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CALIFORNIA PUBLIC UTILITIES COMMISSION

WATER DIVISION

STANDARD PRACTICE FOR

DETERMINATION OF STRAIGHT-LINE REMAINING LIFE DEPRECIATION ACCRUALS

STANDARD PRACTICE U-4-W

SAN FRANCISCO, CALIFORNIA

Revised January 3, 1961

MEMORANDUM

January 3, 1961

CHAPTER 1 66

CHAPTER 2 44

CHAPTER 3 77

CHAPTER 4 1111

CHAPTER 5 1515

CHAPTER 6 2727

CHAPTER 7 3232

CHAPTER 8 3434

CHAPTER 9 3939

CHAPTER 10 4343

CHAPTER 1

SCOPE OF PUBLIC UTILITY DEPRECIATION

Purpose of This Practice

1. This standard practice sets forth various factors influencing the determination of depreciation accruals and describes methods of calculating these accruals. Its purpose is to assist the Commission staff and others in analyzing utility depreciation practices, and in determining proper depreciation expenses when preparing results of operation reports of utilities for rate-making purposes. Particular attention is called to Chapters 3, 4, 5, and 8. These cover the details of the procedures which a staff engineer should be familiar with before undertaking a review of depreciation practices of a utility. Also Chapter 9 discusses general considerations and presents a suggested check list for the engineer.

Basic Depreciation Objectives

2. In the continuing duties of the California Public Utilities Commission in the fixing of rates and the supervision of accounts of utilities under its jurisdiction, a basic depreciation object is that of recovering the original cost of fixed capital (less estimated net salvage) over the useful life of the property by means of an equitable plan of charges to operating expenses or clearing accounts. The straight-line remaining life method presented herein and used as standard procedure by the staff meets this objective. Other depreciation objectives which come before the Commission include determination of a proper deduction for depreciation in the rate base and determination of depreciation values for condemnation proceedings. Since the latter involves specialized considerations this aspect is not further considered in this practice. The matter of deduction for depreciation in the rate base is discussed briefly in Chapter 9.

Concepts of Depreciation

3. In its broad sense the term depreciation as applied to physical property may refer to one or more of the following concepts:

As indicated in the basic objective given above, the cost concept is the one applicable to utility depreciation expenses for rate fixing purposes. This is the concept of depreciation assumed throughout this practice.Accounting Transactions Relating to Depreciation

4. For complete details of the accounting transactions relating to depreciation reference should be made to the appropriate uniform system of accounts for the utility under study. As a reference in using this practice, the following tabulation presents in a broad way the essential transactions:

Definitions of Depreciation

5. The National Association of Railroad and Utilities Commissioners used the following definition: (NARUC Depreciation Committee Report of 1943 and 1944.)

6. The Federal Communications Commission employs the following definition: (Uniform System of Accounts for Telephone Companies, June 19, 1935, p. 4.)

7. Depreciation has been defined by the Supreme Court of the United States as follows: (Lindheimer v. Illinois Telephone Company, 292 U. S. 151, 167 (1934).)

Sinking Fund Method

CHAPTER 2

REMAINING LIFE AND TOTAL LIFE METHODS

The Two Methods

1. In depreciation determinations the life used for computing the accruals may be an estimated total life or an estimated remaining life of property in service. Where the total life plant has been used and original estimates prove inaccurate, excessive or deficient accumulations in the depreciation reserve frequently occur. To overcome this, the use of the remaining life principle has been adopted by many utilities. This practice describes the latter method. However, as a matter of information, a comparison between the two methods is presented in this chapter.

The Total Life Equation for Depreciation

2. The basic formula for total life straight-line depreciation is:

d = (1 - c)/L

3. Thus a steel transmission main for natural gas is constructed at a cost of $100,000. A total life of 20 years with 10% net salvage is estimated. The depreciation rate is:

d = (1 - .10)/20 = .045 or 4.5% per annum

The annual accrual is $100,000 X 4.5% or $4,500.

4. Assuming that no additions to gross plant have been made and that there have been no interim retirements, the depreciation reserve accumulated for this line would at the end of 10 years amount to 45% and at the end of 20 years would amount to 90%, just sufficient to retire the line if net salvage equaled 10%.

Reappraisals of Depreciation Charges

5. Depreciation charges even in the simplest projects should be re-examined from time to time. It is obvious that, until final retirement, depreciation charges involve estimates of future life and salvage. What steps are taken on reappraisal of these estimates?

6. Continuing with the example of the natural gas transmission line, several conditions can be visualized upon reappraisal after, say, 10 years' time has elapsed. One condition may be to reaffirm the view of 10 years ago that the line still has a total life of 20 years and net salvage of 10%, in which ideal case no change in rate is necessary.

7. It is conceivable that the gas line will have a remaining life of only five years, giving a total life of 15 years. On the total life basis, the new rate

d = (1 - .10) / 15 or 6%

8. On the other hand, the reappraisal may indicate a relatively longer life and that the line with suitable repairs or replacements may last 30 years. The new total life rate then becomes

d = (1 - .10) / 30 or 3%

Total Life Theory Inadequate

9. Thus the reappraisals indicate that unless the original estimate of total life proves entirely accurate the total life concept fails to accomplish the solution of the basic problem of charging the cost of fixed capital (less estimated net salvage) to expense over its useful life, and deficits or excesses can arise by reason of changes in service life characteristics or changes in causes of retirement.

The Remaining Life Equation for Depreciation Rate

10. The remaining life straight-line depreciation method is designed to ratably recover the cost of plant, less net salvage and less depreciation reserve, over the remaining life of plant. The formula for this procedure is:

d' = [(1 - c') - u'] / E

11. In the reappraisal in the case of the shorter (15-year) life, the rate becomes

d' = (1 - .10 - .45) / 5 = .09 or 9%

12. For the longer (30-year) life, the rate becomes

d' = (1 - .10 - .45) / 20 = .0225 or 2.25%

13. These conditions are illustrated in the following chart:

(insert scanned chart)

CHAPTER 3

FACTORS INFLUENCING DEPRECIATION ACCRUALS

General

1. Several factors influencing depreciation accruals will be reviewed before considering the actual depreciation accrual. These factors are pertinent to a complete review of depreciation practices of a utility and should be considered by the staff engineer in preparing a report.

Accounting for Plant Additions and Retirements

2. The depreciation computations are normally based on the cost of property recorded on the company's books. Proper accounting records of plant are therefore important. The following points should be checked:

3. Application of the remaining life principle consistently applied over a period of years in connection with a depreciated rate base will normally tend to produce equitable results in rate proceedings even if these points have been incorrectly determined. Nevertheless, it is desirable to stress the maintenance of proper basic plant records.

4. Where feasible, it is desirable that the utility record the dollars in major accounts by year of placement, and relate retirements to the year of placement. This information is necessary where actuarial studies are contemplated in determining estimates of service lives. Such studies are desirable for large groups of property or where the total investment in an account is large. This information will also afford an age distribution of the dollars of plant by year of placement which data permits more accurate determination of remaining lives. These items are discussed in more detail in Chapter 5.

Retirement Pricing and Unit Prices

5. In large group accounts where it is impractical to determine actual costs of each item retired, average unit costs are often used. Determination of unit costs is facilitated if age distribution data are available. Inaccuracies in estimating unit costs or inaccuracies from other causes in pricing retirements, result in distortion of the gross plant and depreciation reserve accounts. While the remaining life method will tend to correct these inaccuracies, it is nevertheless important to obtain reasonable accuracy in the unit retirement costs applied to group accounts.

Unit and Group Bases for Accounting

6. The manner in which the depreciable plant is divided to form the bases on which the accruals are computed is an important factor in the depreciation computation. Where individual property units comprise the base the method is spoken of as unit accounting. Where groups of property, such as an entire account, comprise the base, the method is spoken of as group accounting. The accrual computation presented in Chapter 4 may be used with either base, provided appropriate unit or composite group values for salvage and remaining life are selected. The differences between the two bases may be summarized as follows:

Subaccounts of Plant, Classes of Property and Age Groups

7. To facilitate service life estimates in group accounting or to distinguish between certain recognized parts of a large account, subsidiary data showing subdivisions of an account are often maintained. These include the following:

Inventories and Appraisals

8. Where an inventory and appraisal of the property of a utility has been made, it may be desirable to adjust the books to record the appraisal and related depreciation reserve or to reach some agreed upon restatement in the light of existing facts as a preliminary step in adopting the remaining life method. In such cases appropriate authority of the Commission is needed, and any recommendation to adjust a reserve must be very carefully considered. As discussed in Chapter 4, the book reserve is ordinarily used, but if a restatement of the plant accounts has been approved, the corresponding restated reserve should be used. Once a reserve has been adopted for remaining life method, it should never again be adjusted except to correct accounting errors.

Historical Development of Depreciation Reserve

9. In preparing a report of depreciation practices of a utility, a historical review of past methods of determining credits to the reserve is often helpful. Where initial application of the remaining life method is being made, the considerations of Paragraphs 8 and 9 of Chapter 4 apply. It will be noted that ordinarily the book reserve should be retained and carried forward.

Maintenance Practices and Depreciation

10. In determining the service life of utility plant there is an inherent relationship between maintenance practices and depreciation. By increasing maintenance expenses the service life may often be prolonged, thereby permitting reduced annual depreciation expense. While no exact measure of this relationship is, of course, possible, it is well to inquire into the general level of maintenance when reviewing a utility's depreciation practices. Large maintenance programs will indicate longer service lives are more appropriate while the lack of maintenance program will tend to indicate that lives somewhat shorter than those for otherwise comparable properties would be appropriate. Maintenance practices also affect depreciation when replacement of smaller parts of a major plant unit are made. In a particular account as between two utilities, different service lives for otherwise comparable property will be indicated, if one charges all such replacements to maintenance while the other uses great refinement in retirement units and treats replacements of many smaller units as capital replacements. The latter condition tends to produce shorter service lives for the account, all other factors being equal.

CHAPTER 4

THE REMAINING LIFE DEPRECIATION ACCRUAL DETERMINATION

General

1. This chapter presents the basic steps in determining the straight-line remaining life accrual as of a given date, usually the first of the year, and discusses the source of each element in the accrual equation. Detailed information pertaining to methods of obtaining the element of remaining life expectancy is presented in Chapter 5. Procedures for advancing the determination through the year to cover additions and retirements and for applying the determination in succeeding years are presented in Chapter 8.

The Accrual Equation

2. The basic equation for the straight-line remaining life accrual is:

D' = (B - C' - U') / E

The Standard Form for the Accrual Determination

3. The standard form for the accrual determination is illustrated in Tables 4-A to 4-E which show the complete determinations for typical utilities. This form is available with ruled lines (Form D-1) for work sheet purposes or in the plain style (Form D-2) for finished typing. The form is designated as an annual determination since the results represent an annual accrual or rate.

4. The numbered columns on the form show the elements B, C', and U' of the basic accrual equation in Columns 1, 2, and 3. Column 4 headed "Net Balance" shows the numerator of the equation, Column 5 shows the remaining life expectancy E. The accrual is then computed and shown in Column 6. The lettered columns on the form give supporting information sometimes used in developing the estimated values. Under group accounting a separate line is used for each account or sub account. Under unit accounting a separate line is used for each unit or group of similar units. Ordinarily the accuracy of estimates in the accrual determination is such that the entries may be rounded to the nearest dollar.

Plant in Service

5. The dollars of all depreciable plant in service at the beginning of the year as taken from the utilities' books are used in the accrual determination and entered under the heading "gross plant" in Column 1 of the standard form.

Future Net Salvage

6. Future net salvage as included in the accrual equation represents an estimate of the dollars which will be realized from the future retirement of all units now in service. Net salvage is gross salvage realized from resale, re-use or scrap disposal of the retired units less cost of removal. It is customary to arrive at the net salvage in dollars by applying an estimated percentage to gross plant. Column A of the standard form provides space for entering the estimated percent. The amount in dollars in Column 2 is then the product of the percent in Column A times the plant in Column 1.

7. In estimating the percent net salvage, past experience, when available from the accounting records, should be determined before arriving at a final estimate. However, future conditions often change materially from the past experience because of reduced salvage value of older units or changed conditions in the salvage market or in costs of removal. Also, the past retirement experience of most utility plant is based on but a small portion of today's existing plant. For estimating purposes it is often desirable to consider gross salvage and cost of removal separately. As a rule, gross salvage fluctuates with changes in material costs whereas cost of removal fluctuates with changes in labor expense. Where cost of removal is high, it may be economical, if practicable, to merely abandon plant, which consideration should be reflected in the estimates. It is the usual practice to develop one estimated percent net salvage value for all like units of property. If, however, there is a difference in characteristics or different market demand for units of different ages, the possibility of separate salvage estimates for different age groups should also be considered. When separate estimates are developed for different classes of property or different age groups, the composite estimate for the account should be determined by direct weighting. That is, by multiplying each percent estimate times its related dollars of plant, totaling these products and dividing by the total plant dollars. This gives the composite net salvage expressed as a ratio or a percent. Further detail on procedures used to assist in making salvage estimates is presented in Chapter 7.

Book Depreciation Reserve

8. The dollar balance in the depreciation reserve at the beginning of the year as taken from the company's records should, except in unusual cases, be entered in Column 3 of the standard form and be used in the accrual determination. This book reserve should be retained and carried forward each year by accounts on the remaining life basis. For companies having generally more than $100,000 of gross plant, where the reserve has not been maintained by accounts, the initial application of the remaining life method will require an allocation of the reserve by primary accounts. Companies with less than $100,000 of plant may, as an alternative, compute an over-all composite accrual as described in Paragraph 12 below.

9. An allocation of the reserve by accounts if required should be based on prorating the book reserve according to the reserve requirement or upon a historical reconstruction of the reserve for each account where records are available. If the reserve has previously been kept by groups of accounts or by departments, the allocation to accounts should be made within the group or department without disturbing these subtotals. It will be noted that a reserve requirement study is not required once the remaining life method is started and carried forward. Reserve requirement studies will not be made by the staff, except for the initial allocation to primary accounts, or except in special cases recommended by the Branch Engineer and approved by the Director or Assistant Director of the Utilities Division. Details of procedure when a requirement study is to be made should be reviewed with the Staff Advisory Section.

Remaining Life Expectancy

10. The remaining life in years to be entered in Column 5 of the standard form represents the composite remaining life expectancy for all units, age groups, and classes of property of the account at the beginning of the year. A determination of this value may be made by any one of several methods. The choice of method depends on a number of factors, particularly upon the data available from accounting and engineering records and upon the practical aspects of time and work economy. Details of the various methods and their applicability are discussed in the next chapter. Where the remaining life is determined directly, no entries need be made in Columns B, C or D on the standard form. Where the remaining life is determined from estimates of other service elements the latter should be entered in the appropriate columns.

Depreciation Accruals

11. Having completed entries in Columns 1, 2, 3, and 5 of the standard form, the annual accrual for conditions as of the first of the year may be computed as indicated on the form. It may be used directly as the total accrual for the year or may be adjusted for plant additions as discussed in Chapter 8.

Alternate Accrual Determination for Small Utilities

12. Utilities having generally less than $100,000 of total plant, who elect not to separate the reserve by accounts as discussed in Paragraph 8 above, will have but one total entry in Column 3. Under these conditions, it is appropriate to develop a composite value for remaining life for the entire plant. The total accrual is then obtainable by completing the determination across the totals line only on the standard form. The two alternate examples of Tables 4-D and 4-E illustrate the solution.

13. To develop a composite value of the remaining life from separate estimates by accounts, reciprocal weighting may be used as an approximation as follows:

14. Further simplification for utilities having generally less than $25,000 of plant may be made by omitting estimates for each account and developing by direct judgment a remaining life estimate for the entire plant.

(insert 5 pages here)

CHAPTER 5

METHODS OF ESTIMATING THE REMAINING LIFE EXPECTANCY

General

1. There is presented in this chapter: first, material on the general nature of remaining life estimates and plant mortality; second, the types of data available from which remaining life estimates may be developed; third, methods of weighting and a discussion of the factors governing the selection of a method; fourth, a brief presentation of the available methods of estimating remaining life; and, finally, a discussion of the governing factors and procedures in the selection of a method. Each of these items comprises a separate section of the chapter. Those familiar with depreciation practices, or those interested in an over-all picture, only, may wish to turn directly to the final section commencing at Paragraph 18.

A - REMAINING LIFE AND PLANT MORTALITY

Basic Nature of the Remaining Life Estimate

2. Determination of the remaining life basically involves the judgment estimate of the engineer as to the future effect of wear and tear, decay, action of the elements, inadequacy, obsolescence, and public requirements. In special cases other factors may be important, such as anticipated changeovers to new or improved major units of plant, and other specific plans of management. To arrive at a satisfactory estimate of future conditions, the past experience generally gives indications which may be used as a major element in the remaining life estimate. The weight to be given past experience depends upon the extent to which conditions affecting service life in the future are expected to be similar to or different from those in the past. However, substantial weight is generally given to results of past experience in the same or comparable properties.

Plant Mortality Experience

3. From the numerous studies of utility properties made by many individuals and organizations under widely varying circumstances, it is known that large groups of like plant generally follow a mortality pattern. This pattern is such that the portion of an original group surviving at a time may be statistically predicted as a function of age. A graph or curve illustrating this relationship is known as a survivor curve. Chart 5-A illustrates a survivor curve together with various related curves and service life elements. The more important service life elements include the following

B - DATA AVAILABLE FROM UTILITY RECORDS

Sources of Data

1. Data available from utility records affording information on which to base estimates may be found among the following sources:

2. Each of these sources should be checked with a view toward arriving at all available pertinent information. The more important types of information to be assembled as a basis for estimating lives are discussed in the next five paragraphs.

Mortality Summary Data

3. The mortality summary of an account or class of property provides the most reliable source for developing past results and statistically predicting future experience. Such a summary sets forth the dollars or units of plant placed each year and shows the related retirements by age at retirement. This information, when not maintained directly, may frequently be developed by study from those sources listed under Items b, c, d, and e in the preceding paragraph. In order to maintain this information it is necessary to record the dollars in each account by year of placement and relate retirements to year of placement. Where the group comprises many small units, this is sometimes accomplished by studies of representative samples. For accounts or single classes of property with over approximately $100,000 in plant, the accumulation of this data when at all feasible is recommended.

4. From the mortality summary, using actuarial methods, smoothed and extended survivor curves applicable to the plant in question may be developed. Available alternate methods of solution of the data include both the stub survivor curve directly, selecting a type curve by matching with the stub curve, smoothing the observed survivor ratios or retirement ratios, and smoothing the observed frequency curve. These various elements are illustrated in Chart 5-A. Complete details for using these methods are beyond the scope of this practice. Where data are available and the staff is to determine a solution, assistance of the Water Advisory Branch should be obtained. Where review of a utility's solution is made, the reasonableness of the band of years of past experience selected as representative of future conditions should be checked.

Distribution Data

5. Distribution data, when available, permits accurate development of remaining life from a selected survivor curve. These data show the dollars of plant surviving separated by age groups. Where mortality summaries are maintained, these data may be taken direct from the summary. In other cases, although mortality summary data are not available, age distribution data may be developed. This can be done by (?) from accounting records based on known placements or retirements of major units coupled with a first-in first-out treatment of unidentified additions and retirements. The first-in first-out treatment of additions and retirements is to be used with caution, particularly if applied to an entire account, for it distorts the mortality dispersion experience. An alternate and perhaps more accurate means of initially developing distribution data is to select an applicable survivor curve and apply the portion surviving for each age to known gross additions each year. The first four columns of standard form D3 provide for this calculation as illustrated in Table 5-A. When an age distribution study has been made, it is desirable if feasible, that all information thereafter be carried forward annually, particularly for accounts exceeding $100,000 in value.

6. Distribution data is sometimes used to determine age dollar and average age information. Determination of the remaining life of a group account by subtracting average age from an estimated average probable life is an approximation subject to possible wide error in results. Whenever a survivor curve believed reasonably representative of future condition may be selected, even if a type curve is selected on a judgment basis, the remaining life result, obtained by direct weighting as described below, is to be preferred over determining an average age and applying the group approximation.

(where are paragraphs 7 and 8?)

(insert two pages here)

Accounting Records of Gross Additions and Plant Balances

9. Where mortality summary data and age distribution data are not developed, considerable information on which to base estimates may be developed from the plant accounting records maintained in conformance with the uniform systems of accounts. Some caution must be exercised, however, to eliminate the distortion caused by transfers and adjustments to accounts, by changes in accounting classification, and by abnormally large retirements or replacements of units. Use of these data yields more reliable results in accounts with stable plant or plant with uniform growth where no noticeable trend toward longer or shorter service lives is evident. With these precautions in mind the following may be developed:

C - METHODS OF WEIGHTING

Types of Weighting

10. Before considering the methods for obtaining remaining life it is well to consider the means by which estimates for separate classes of property or separate age groups may be weighted to afford a composite value. Three types of weighting are used as follows:

Selecting a Method of Weighting

11. In selecting a method of weighting, several considerations apply. First, it is desired that the method of weighting used shall produce the same results as though the book reserve had been prorated to the various age groups or classes of property on the basis of the applicable reserve requirement. Secondly, it is desirable that the result obtained by weighting be in conformance with the provisions of certain of the uniform systems of accounts, that the accrual computed for an account as a whole shall be the same as if separate accruals had been computed for each class of property and the total obtained. Under these considerations, direct weighting produces proper results if the average service life of each age group or class of property weighted is approximately the same. Reciprocal weighting produces proper results if the reserve for the various classes of property or groups weighted is distributed in proportion to the plant dollars, a condition which is more likely in stable plant with slow growth. Average service life weighting produces proper results which is more likely in stable plant with slow growth. Average service life weighting produces proper results if the book reserve and the reserve requirement are closely the same. From these considerations it is concluded that direct or future dollar weighting is the proper method to use between age groups, whereas either reciprocal weighting or average service life weighting will usually yield the better approximation between classes of property. In very large accounts where individual classes of property exceed $100,000 of plant, occasionally a utility may prefer to prorate the book reserve within the account according to a reserve requirement between each class of property rather than to attempt any of the other weighting methods. Such a proration is used only infrequently, is made only at the time of a periodic review for weighting purposes within a very large account, and is normally not carried forward from the date of the calculation.

D - AVAILABLE METHODS OF ESTIMATING REMAINING LIFE

Survivor Curve Methods

12. If a survivor curve believed representative of future conditions can be developed or a type survivor curve is selected on a judgment basis, the determination of the remaining life is greatly facilitated. Standard form D4 provides for computing the elements of a survivor curve as illustrated in Table 5-C. Where mortality summary data are available, the curve should be developed from these data. Care should be exercised to select data from a band of years reasonably representative of the anticipated future conditions. In determining the shape of the extended portion of the curve, it is helpful to ascertain a reasonable maximum life or cutoff point for the curve. Other factors such as the operation of uniform chance retirement which produces a flat curve and the possibility of high early mortality which produces an early drop in the curve, or similar factors should be kept in mind. Usually it will be evident from the summary data that certain of these factors are operating in the plant and the calculated results will reflect these conditions.

13. When mortality summary data are not available the selection of a general type survivor curve is desirable. In selecting type curves the considerations enumerated in the preceding paragraph are applicable. Type curves may be obtained from actuarial analyses made of mortality data of comparable classes of property in comparable utilities or they may be obtained from general studies. One widely accepted study of this latter type is that conducted at the Iowa State College Engineering Experiment Station as described in their Bulletins Nos. 125 and 155. These curves are referred to in this practice as Iowa type curves. Tabulations of remaining lives by ages for each Iowa curve are given in the appendix. It will be noted that a particular type curve is identified by two elements. One is the average service life and the other is the type designator. The latter designates the general shape of the curve. When selecting the survivor curve on a judgment basis, the average service life must be estimated and an appropriate survivor curve shape selected. Turnover studies or related experience in other properties offer a guide to selecting an average service life. As a guide in selecting Iowa type curves, "L" types designate curves indicating high early mortality, "S" types designate curves with maximum retirements occurring about the mid-span of years, and "R" types designate curves with few early retirements and heavy retirements near the end portion of the curve. For each of these groups the higher subscripts indicate progressively greater concentration of retirements at one period.

14. Another method of developing a survivor curve is the simulated plant balance approach which involves a mathematical selection of that survivor curve which applied to the gross addition year by year will match the recorded year by year balances of the plant account. This method is applicable only where it is determined that past mortality experience has been consistent between generations and is reasonably indicative of the future. It is not applicable to plant accounts where substantial technical changes in the facilities have occurred. Two procedures have been advanced for developing the "simulated" balance solution. One procedure involves the successive trial of a number of curve patterns applied to the known additions to select the curve which most closely matches the actual plant balances. A complete discussion of this procedure using a set of precalculated tables based on the Iowa type curves is found in the paper entitled "Life Analysis of Utility Plant and Depreciation Accounting Purposes by the Simulated Plant Record Method" by A. E. Bauhan. The second procedure involves the use of the actual plant balances in the development of an equation for an approximate survivor curve of a predetermined generic type. A complete discussion of this procedure is set forth in a paper entitled "Mortality Curves for Physical Plant" by J. F. Brennan. Copies of these papers are in the Commission staff files (Staff Advisory Section).

Forecast Method

15. In certain accounts such as buildings, structures, telephone central office, dams, reservoirs, generating plants and other classes of property comprised of major units which it is expected will be retired as a single unit at one time, the development of an appropriate remaining life is more readily accomplished by direct estimate. This method is referred to as the Forecast Method or in some cases, the Life Span Method. The tabulation below shows a sample calculation using this method. First step in the procedure is to list each major unit of property included in the account together with its relating plant dollars surviving today (Columns 1 and 3). Next, a direct judgment estimate is made of the remaining service span or the terminal date when each unit will be retired (Columns 4 and 5). To the remaining span a small correction is applied for so-called "interim retirements" of smaller units comprising part of the major unit. Interim retirements and additions include such items as changes within a building or changes at an electrical generation station not altering the basic structures, etc. As an approximation the assumption is made that future annual interim retirements will occur at a consistent ratio to the present plant balance (Column 6). The correction for interim retirements is then developed by picturing the resulting survivor curve shape. The major unit of property with its forecasted terminal date is represented by a square-shaped survivor curve. The interim retirements cause the top of this square to slope downward to the terminal date when the entire unit is retired. The correction for interim retirements is then the area of the triangle lost at the top of the square by reason of the interim retirements. The base of this triangle is the remaining span. The depth (height of this triangle) is the interim retirement rate times the number of years during which they will continue, namely, the interim retirement rate times the remaining span. The correction for interim retirements (Column 7) is then the area of this triangle, or one-half times the interim retirement rate times the remaining span squared. In more accurate applications, this correction may be developed from an actuarial analysis of mortality data for the interim retirements. After applying the correction to obtain the effective remaining life (Column 8), the composite remaining life for the account is obtained by direct weighting with the dollars for each unit (Column 9). However, average service life weighting is more appropriate where only a few items occur in an account and a long time interval exists between the extreme probable retirement dates.

Approximation Method

16. Where survivor curves cannot be selected and the forecast method is not applicable, indications of remaining life may be obtained from the accounting records of gross additions and plant balances. Standard form D-5 provides for calculation by this method as illustrated in Table 5-D. The method is subject to the limitations discussed in Paragraph 9 above. However, indications may be obtained from a short span of years thereby avoiding some of the inconsistencies occasionally found in accounting data. Referring to Table 5-D, to apply the method, the starting plant balance, Item (4), plus the total gross additions (1) for a span of years is totaled to give plant exposed (6). The total of the plant balances (3) less one-half the beginning balance (5) and less one-half the ending balance (8) for the same span of years is likewise totaled (10) and a correction for past dollar years for transfers (11) is made to obtain Past Dollar Years (13). The quotient of these two totals [(13) divided by (6)] represents the realized life (14) of the plant during the span of years selected. The plant surviving at the end of the span (7) divided by the total of gross additions (6) indicates the portion of exposed plant surviving (9). The remaining life (16) has been obtained by selecting an appropriate average service life (12), subtracting from this the realized life (14) and dividing this difference (15) by the portion surviving (9).

Direct Judgment Method

17. Where lack of appropriate data and other considerations make the application of any of the preceding methods unavailable, direct engineering judgment estimates of service life expectancies may be appropriate. It should be helpful to the engineer to study possible ranges of life estimates, setting down reasonable minimum and maximum expectancies before coming to final conclusions. Likewise, where the judgment method is being used, it may be desirable to consider the relationship of age plus remaining life which equals probable life. As previously noted at any age the probable life of survivors equals the age plus remaining life expectancy. This relationship is strictly true only for groups with all units of one age whose probable life is correctly estimated. However, the relationship is of value in determining a judgment estimate of remaining life. It should be noted that the average life of all units originally placed in the group, is less than the probable life of surviving units because of the prior retirement of short-lived units.

E - CHOOSING A METHOD OF ESTIMATING REMAINING LIFE

Steps in Choosing a Method

18. As can be seen from the foregoing, the methods available for estimating remaining life range in detail and accuracy from full actuarial analysis with age group weighting, through various approximation methods, to the simple direct judgment selection of a value for "E". In choosing a particular method best suited to the property in question the engineer should first have in mind the general nature of plant mortality characteristics and pertinent experience in similar properties; second, he should determine the type data available from the utilities' records; third, he should evaluate available methods in relation to the size of plant and the practical aspects of accuracy and work economy; and, finally, consistent with all the foregoing, he should select a method designed to yield the greatest accuracy practicable. Oftentimes it may be desirable to use different methods for different accounts and sometimes even for different classes of property within the same account. These steps are discussed in detail in the remaining paragraphs of this chapter.

Step One: "Have in mind the general nature of plant mortality characteristics and pertinent experiences in similar properties."

19. Paragraphs 2 and 3 of this chapter provide a basis for this information. Also the staff engineer should review recent depreciation studies of comparable utilities, and make a field inspection of the properties. For the larger utilities, experience in comparable accounts of the same utility should be noted. Other background information on mortality characteristics is covered in Chart 5-A and in Chapter 6.

Step Two: "Determine the type of data available form the utilities' records."

20. Paragraph 4 enumerates some sources of data. Paragraphs 5 through 9 discuss types of data which may be assembled to aid in determining estimates. The various factors of Chapter 3 as applied to the utility in question are also pertinent. Particular attention should be given to the methods used in determining unit retirement costs or retirement charges. Often appropriate mortality summary or age distribution data may be assembled from the unit cost data. One further consideration should be undertaken in this step; namely, the base for individual estimates should be fixed. Thus the classes of property within each account should be considered and those to be treated separately in the estimates should be selected. The presence of district mortality characteristics and the availability of data to permit separate estimates are criteria to be considered in this selection.

Step Three: "Evaluate available methods in relation to the practical aspects of accuracy and work economy.

21. The available methods are described in Paragraphs 13 through 17 above. Certain methods, as indicated, require detailed technical knowledge for which qualified personnel may not be available to smaller utilities. Different degrees of approximation are involved in each method. Generally, the more approximate methods are easier to apply but are subject to greater possibility of error. Considering the methods solely form the standpoint of accuracy, the preferable methods may be enumerated in the following order:

Step Four: "Select a method designed to yield the greatest accuracy practicable."

22. The final selection of a method will be somewhat apparent from the foregoing steps. Limitations on available data will result in deletion of some methods; smaller utilities will lack qualified personnel to perform some of the more accurate methods, etc. As a general guide, it is desirable to apply a survivor curve wherever possible. From a survivor curve weighting by age groups may be applied as illustrated in Tables 5-A and 5-B. The standard form for this calculation is designated Form D-3. Space is provided on the form for deriving age distribution data from gross additions and a selected survivor curve. Where the survivor curve is determined by actuarial analysis, or where age distribution data are otherwise available, Columns 2 and 3 of the form need not be used. Where the Iowa type curves are selected the appropriate remaining life to be entered in Column 5 may be taken from the tabulations given in the Appendix. To aid in testing the reasonableness of final results, some typical average service lives are given in Chapter 6. These typical results may be helpful, but they are to be used with caution.

23. The final selected value of the remaining life as previously discussed should be entered in Column 5 of the standard determination form D-1 or D-2. Where estimates of average service life, probable life, or average age were used to develop the remaining life estimate, these values should be shown in Columns B, C, and D of the standard determination form.

Choosing a Method for Smaller Utilities

24. The preceding discussion of the steps in choosing a method to be used for estimating the remaining life expectancy is applicable to utilities of all sized. However, smaller utilities having limited technical personnel available or having a minimum of records relating to plant additions and retirements, will find but one or two methods applicable. As a general rule, the utilities having less than $100,000 of plant must rely largely on the Judgment Method described in Paragraph 17. These utilities may also occasionally use the Forecast Method described in Paragraph 15.

CHAPTER 6

TYPE CURVES AND TYPICAL EXAMPLES OF

SERVICE LIFE ESTIMATES

Applicability of This Material

1. The material presented in this chapter is offered as an aid in formulating engineering estimates of service life expectancies. Application of these data to a particular group of properties must be based on knowledge of local conditions, company policy with regard to retirements and other factors influencing service life.

Ranges of Typical Average Service Lives

2. The following tabulations give ranges which have been selected a typical for values of straight-line average service lives used by utilities in California. Also shown is a suggested method for an average utility to use in estimating remaining lives of the indicated account.

Ac. No.

Old New*

Class of Plant

Total Service Life of an Original Group (Av. Service Life

in Years)

(See Notes 1, 2)

Suggested Method Estimating Remaining Life

(See Note 5)

   

A. Electric Utilities

   
   

PRODUCTION PLANT

   
   

Steam Production

   

311

311

Structures and Improvements

40-60

Forecast

312

312

Boiler Plant Equipment

30-40

Forecast

314

314

Turbogenerator Unit

35-45

Forecast

315

315

Accessory Electric Equipment

25-45

Forecast

316

316

Miscellaneous Power Plant Equip.

15-30

Forecast

         
   

HYDRAULIC PRODUCTION

   

321

331

Structures and Improvements

30-100

Forecast

322

332

Reservoirs, Dams and Waterways

75-100

Forecast

323

333

Water Wheels, Turbines, and Generators

35-50

Forecast

325

335

Miscellaneous Power Plant Equipment

35-60

Forecast

326

336

Roads, Railroads and Birdges

35-75

Forecast

         
   

OTHER PRODUCTION

   

331

341

Structures and Improvements

35-60

Forecast

332

342

Fuel Holders, Producers and Acces.

15-25

Survivor Curve

333

343

Prime Movers

15-25

Survivor Curve

334

344

Generators

15-25

Survivor Curve

335

345

Accessory Electrical Equipment

15-25

Survivor Curve

336

346

Miscellaneous Power Plant Equipment

15-25

Survivor Curve

         

* Effective January 1, 1961 by Decision No. 61160.

Notes: 1. Plant of a particular utility may justify a service life outside of above ranges.

      2. Net salvage estimates are to be separately considered.

      3. Larger utilities will find more accurate methods, such as selection of a type curve or actuarial solutions, desirable. Small utilities may find only the Approximation Method or the Judgment Method applicable. For further information, see Chapter 5, Section E.

Ac. No.

Old New*

Class of Plant

Total Service Life of an Original Group (Av. Service Life

in Years)

(See Notes 1, 2)

Suggested Method Estimating Remaining Life

(See Note 5)

   

A. Electric Utilities - continued

   
   

TRANSMISSION PLANT

   

342

352

Structures and Improvements

35-50

Forecast

343

353

Station Equipment

25-50

Forecast

344

354

Towers and Fixtures

35-55

Survivor Curve

345

366

Poles and Fixtures

25-35

Survivor Curve

346

356

Overhead Conductors and Devices

35-50

Survivor Curve

347

357

Underground Conduit

40-50

Survivor Curve

348

358

Underground Conductors and Devices

25-35

Survivor Curve

349

359

Roads and Trails

50-75

Judgment

         
   

DISTRIBUTION PLANT

   

351

361

Structures and Improvements

35-50

Forecast

352

362

Station Equipment

25-35

Forecast

354

364

Poles, Towers, Fixtures

25-50

Survivor Curve

355

365

Overhead Conductors and Devices

25-35

Survivor Curve

356

366

Underground Conduit

40-50

Survivor Curve

357

367

Underground conductors and Devices

25-35

Survivor Curve

358

368

Line Transmissions

25-35

Survivor Curve

359

369

Services

20-35

Survivor Curve

360

370

Meters

25-35

Survivor Curve

361

371

Installations on Customers Premises

35-30

Judgment

363

373

Street Light and Signal Systems

15-30

Survivor Curve

         
   

GENERAL PLANT

   

371

390

Structures and Improvements

30-75

Forecast

372

391

Office Furniture and Equipment

15-25

Survivor Curve

373

392

Transportation Equipment

5-20

Judgment

374

393

Store Equipment

15-25

Judgment

375

394

Tools and Shop Equipment

10-30

Survivor Curve

377

376

395

Laboratory Equipment

15-30

Judgment

378

379

Communication Equipment

10-25

Judgment

379

398

Miscellaneous Equipment

15-25

Judgment

         
         

* Effective January 1, 1961 by Decision No. 61160.

Notes: 1. Plant of a particular utility may justify a service life outside of above ranges.

      2. Net salvage estimates are to be separately considered.

      3. Larger utilities will find more accurate methods, such as selection of a type curve or actuarial solutions, desirable. Small utilities may find only the Approximation Method or the Judgment Method applicable. For further information, see Chapter 5, Section E.

Ac. No.

Old New*

Class of Plant

Total Service Life of an Original Group (Av. Service Life

in Years)

(See Notes 1, 2)

Suggested Method Estimating Remaining Life

(See Note 5)

   
B. Gas Utilities
   
   

UNDERGROUND STORAGE

   

342

351

Structures and Improvements

25-60

Forecast

343

352

Wells

25-40

Forecast

343.3

353

Lines

25-50

Survivor Curve

343.4

354

Compressor Station Equipment

25-30

Forecast

343.5

355

Measuring and Lighting Equipment

25-30

Survivor Curve

343.6

356

Purification Equipment

25-30

Survivor Curve

343.7

357

Other Equipment

25-50

Judgment

         
   

LOCAL STORAGE PLANT

   

346

361

Structures and Improvements

35-60

Forecast

347

362

Gas Holders

40-50

Forecast

348

363

Other Equipment

25-50

Judgment

349

         
   

TRANSMISSION PLANT

   

352

366

Structures and Improvements

25-35

Forecast

353

367

Mains

25-45

Survivor Curve

354.1

368

Compressor Station Equipment

25-30

Forecast

354.2

369

Measuring and Regulating Equipment

25-30

Survivor Curve

355

371

Other Equipment

15-30

Judgment

         
   

DISTRIBUTION PLANT

   

358

375

Structures and Improvements

30-50

Forecast

359

376

Mains

35-60

Survivor Curve

360.1

377

Compressor Station Equipment

15-35

Forecast

360-2

378

Measuring and Regulating Equipment - General

15-25

Survivor Curve

361

380

Services

25-45

Survivor Curve

362

381

Meters

25-40

Survivor Curve

363

382

Meter Installation

25-40

Survivor Curve

364

383

House Regulators

25-35

Survivor Curve

365

384

House Regulator Installations

30-35

Survivor Curve

366.1

385

Industrial Meas. & Reg. Equip.

15-30

Survivor Curve

366

386

Other Property on Customers' Premises

15-30

Judgment

367

387

Other Equipment

15-40

Judgment

         
   

GENERAL PLANT

   

371

390

Structures and Improvements

30-75

Forecast

372

391

Office Furniture and Equipment

15-25

Survivor Curve

373

392

Transportation Equipment

5-20

Judgment

374

393

Stores Equipment

15-25

Judgment

375

394

Tools, Shop and Garage Equipment

10-30

Judgment

376

395

Laboratory Equipment

15-30

Judgment

378

397

Communication Equipment

10-25

Judgment

379

398

Miscellaneous Equipment

15-25

Judgment

 

* Effective January 1, 1961 by Decision No. 61160.

Notes: 1. Plant of a particular utility may justify a service life outside of above ranges.

      2. Net salvage estimates are to be separately considered.

      3. Larger utilities will find more accurate methods, such as selection of a type curve or actuarial solutions, desirable. Small utilities may find only the Approximation Method or the Judgment Method applicable. For further information, see Chapter 5, Section E.

Ac. No.

Class of Plant

Total Service Life of an Original Group (Av. Service Life

in Years)

(See Notes 1, 2)

Suggested Method Estimating Remaining Life

(See Note 5)

         
   
C. Telephone Utilities
   

207

 

Right of Way (when depreciable)

40-70

Judgment

212

 

Buildings

25-60

Forecast

221

 

Central Office Equipment

30-45

Forecast

231

 

Station Apparatus (fixed capital life basis)

15-25

(Various)

235

 

Large Private Branch Exchanges

15-40

Forecast

241

 

Pole Lines

20-40

Survivor Curve

242.1

 

Aerial Cable

20-35

Survivor Curve

242.2

 

Underground Cable

25-40

Judgment

243

 

Aerial Wire

10-25

Survivor Curve

244

 

Underground Conduit

50-75

Judgment

261

 

Furniture and Office Equipment

15-35

Judgment

264

 

Motor Vehicles and Other Work Equipment

5-20

Judgment

         
   
D. Water Utilities
   
   

SOURCE OF WATER PLANT

   

311

 

Structures and Improvements

20-60

Forecast

312

 

Collecting and Impounding Reservoirs

40-100

Forecast

313

 

Lake, River and Other Intakes

30-70

Forecast

315

 

Wells

20-40

Forecast

316

 

Supply Mains

25-100

Forecast

         
   

PUMPING PLANT

   

321

 

Structures and Improvements

20-60

Forecast

324

 

Pumping Equipment

15-35

Survivor Curve

325

 

Other Pumping Plant

15-25

Judgment

         
   

WATER TREATMENT PLANT

   

331

 

Structures and Improvements

20-60

Forecast

332

 

Water Treatment Equipment

15-40

Forecast

         
   

TRANSMISSION AND DISTRIBUTION PLANT

   

341

 

Structures and Improvements

20-60

Forecast

342

 

Reservoirs and Tanks

25-100

Forecast

343

 

Transmission and Distribution Mains

   
   

Cast Iron and Asbestos Cement

50-100

Survivor Curve

   

All Other Pipes

25-50

Survivor Curve

345

 

Services

20-40

Survivor Curve

346

 

Meters

25-40

Survivor Curve

347

 

Meter Installations

25-45

Survivor Curve

348

 

Hydrants

25-50

Survivor Curve

349

 

Other Transmission and Distribution Plant

15-40

Judgment

         
         

Notes: 1. Plant of a particular utility may justify a service life outside of above ranges.

      2. Net salvage estimates are to be separately considered.

      3. Larger utilities will find more accurate methods, such as selection of a type curve or actuarial solutions, desirable. Small utilities may find only the Approximation Method or the Judgment Method applicable. For further information, see Chapter 5, Section E.

Ac. No.

Class of Plant

Total Service Life of an Original Group (Av. Service Life

in Years)

(See Notes 1, 2)

Suggested Method Estimating Remaining Life

(See Note 5)

         
   

GENERAL PLANT

   

371

 

Structures and Improvements

20-60

Forecast

372

 

Reservoirs and Tanks

5-20

Survivor Curve

373

 

Transportation

5-20

Judgment

374

 

Stores Equipment

5-25

Judgment

375

 

Laboratory Equipment

5-25

Judgment

377

 

Power Operated Equipment

5-25

Judgment

378

 

Tools, Shop and Garage Equipment

5-25

Survivor Curve

         

Notes: 1. Plant of a particular utility may justify a service life outside of above ranges.

      2. Net salvage estimates are to be separately considered.

      3. Larger utilities will find more accurate methods, such as selection of a type curve or actuarial solutions, desirable. Small utilities may find only the Approximation Method or the Judgment Method applicable. For further information, see Chapter 5, Section E.

Iowa Type Survivor Curves

3. There are presented in the tables in the Appendix the portions surviving and remaining lives by ages for various average service lives for the 18 type curves developed at the Iowa State College Experiment Station. Remaining life expectancies have been computed form the data given in Bulletin 125, 155 and 156 issued by the Iowa college. These curves are referred to as "Iowa" type curves or as "Winfrey" type curves. The former designation is adopted in this practice. The latter designation refers to Professor Robley Winfrey, author of these Iowa bulletins.

4. A tabulation indicating curve types found applicable to certain classes of plant is also shown in the appendix. The indicated applicability of these curves is, of course, only general in nature and is largely based on the experience of the Iowa studies. In particular instances, the engineer may determine other type curves to be more specifically applicable than these general studies.

5. The portions surviving shown in the Iowa tables may be used to develop age distribution data as illustrated in table 5-A, and the remaining lives shown may be used to develop a composite remaining life from age distribution data as illustrated in Tables 5-A and 5-B.

6. A more compete set of Iowa type survivor and average remaining life tables has been compiled by Edison Electric Institute and American Gas Association. The tables give survivors of an original addition of 1,000 and corresponding average remaining lives to the nearest tenth of a year at half-year ages from 0.5 to 74.5, inclusive, for average lives from 5 to 100 years, inclusive. The tables were computed for the familiar mortality dispersion curves listed in the Iowa Bulletins, for dispersion intermediate to those in the bulletins and for two other type curves, SC and SQ. The curve designated SC is the Patterson C type curve, having a uniform distribution of retirement form age zero to twice average life. The designation SQ is for the square type survivor curve which ahs no mortality dispersion, i.e., all retirements occur at average life(at terminal life).

CHAPTER 7

DETERMINATION OF GROSS SALVAGE

AND COST OF REMOVAL

1. The detailed procedures presented below are applicable to larger utilities or larger accounts where they may be used as an aid in arriving at estimates of proper future net salvage. This material supplements Paragraphs 6 and 7 of Chapter 4 which present the basic consideration. Net salvage is defined as gross salvage realized from resale, re-use or scrap disposal of the retired units less cost of removal.

Determining Recorded Salvage Experience

2. Where records are available recorded salvage experience for each account may be determined by analyzing the credits and debits to the reserve. To do this, total the retirements for each year and determine the corresponding totals of gross salvage and cost of removal. Dividing each of the latter by the retirements gives the percent gross salvage and percent cost of removal realized for each year. This calculation for a series of years is illustrated in the upper portion of the examples shown in Tables 7-A and 7-B using standard form D-6. In using this information for determining estimates it is often helpful to plot a graph of successive values each account, it may be desirable to make a determination for all accounts as a whole to test the over-all reasonableness of the various estimates.

Future Gross Salvage

3. In most classes of property the percent gross salvage realized on retirement varies with the age of the unit. Generally, the older units yield lower values. Past experience is usually based on but a few retirements, probably of shorter-lived units; therefore, future gross salvage will usually be less than the recorded experience. For very accurate determinations predicted salvage values by ages should be weighted with predicted retirements by ages. As an approximation, however, reasonable results may be obtained by assuming a straight-line diminution from realized gross salvage of early retirements to the predicted ultimate gross salvage of oldest-lived units. The sample calculation shown in part 2 of Table 7-A illustrates an application of this assumption. The past experience for a recent span of years is noted. Anticipated ultimate gross salvage of the oldest surviving units is then estimated and an average of these two values is selected as the anticipated future gross salvage applicable to today's plant. In predicting ultimate gross salvage of older-lived units for certain classes of property such as cable, wire, buildings, motor vehicles and similar items, market conditions in the future may influence the results more than any other factor. The engineer should use reasonable market predictions for the immediate future as though applicable throughout the property life. Corrections for long-term changes in the market may be made, if necessary, at the time of periodic reviews under the remaining life plan.

(skipped two pages)

Future Cost of Removal

4. As pointed out in Chapter 4, cost of removal is essentially a labor cost. Predicted future cost of removal should be based on a reasonable projection of recent experience reflecting anticipated changes in labor cost for the immediate future. Possible abandonments of plant, or changes in cost of removal when resale of a plant item is not planned, are future factors to consider.

Accounts With High Turnover and Re-use of Plant

5. In certain accounts, notable the station apparatus account of telephone utilities, the placement and retirement of property units may be recorded on a location basis while the actual unit is retained and used successively at several locations during its "fixed capital" or physical life. Under these conditions the net salvage is a composite of the value for retirements where re-use occurs and the value at final retirement. The composite estimate of future net salvage may be arrived at by weighting separate service life and salvage estimates as illustrated in the following example:

CARRYING FORWARD THE ACCRUAL DETERMINATION

Problems in Carrying Forward the Accrual

1. The depreciation accrual determined from standard form D-1 or D-2 is based on plant balance, book reserve and remaining life as of the beginning of the year. For each account where a complete study has been made in developing this determination three problems arise in applying it to the utilities' books and carrying it forward. First, the accrual to record for the study year is needed. Next, it is necessary to consider the means of determining accruals in the intervening years before another complete study of the account is made. Finally, the length of period between complete studies should be considered, it being inherent in the remaining life method that periodic reviews of estimates and reappraisals to correct for changing conditions will be made. These three problems are discussed under separate subheadings below. However, before turning to these, there is first presented material on accounting procedures for crediting the accruals and determination of the depreciation rates which are applicable to the problems.

Accounting Procedures for Crediting the Accruals

2. Several methods for recording the accrual on the books of a utility at the time of a study are used. These may be summarized as follows:

3. During intervals between complete depreciation studies, the methods used to determine accruals include the above methods carried forward plus some additional methods involving partial redeterminations from the basic estimates. The various alternatives may be summarized as follows:

Determining Depreciation Rates

4. The standard forms D-1 or D-2 for the accrual calculation provide space in Column E for computing the remaining life depreciation rate for each account. This rate is obtained by dividing the accrual in Column 6 by the plant in Column 1. It is usually expressed in percent, that is, as a percent of gross plant. The composite deprecation rate for the entire depreciable property is obtained by dividing the total of Column 6 by the total of Column 1.

Selecting a Method of Determining the Study Year Accrual

5. Ordinarily the staff engineer in reviewing depreciation practices of a utility will apply the accounting procedure currently used by the utility. However, where a procedure is being established or a change is indicated other considerations may apply. Briefly, method a in paragraph 3 above, is the simplest and is used by some large as well as some small utilities, methods b and c yield results based on average plant which conforms to the procedure used in determining rate base, while method d as noted above is not recommended. As between methods b and c, the latter is more applicable to larger utilities where monthly balances are available and greater accuracy may be desired. For smaller utilities, method b is recommended for staff use.

Selecting a Method for Determining the Accrual in Years Between Studies

6. When determining the accrual in the intervening years between complete studies of an account, methods a, b, and c of Paragraph 3 above, which use the depreciation rate developed at the time of the last study applied to new plant balances, yield reasonable results with a minimum of calculation. When selecting as between these three methods, the considerations discussed in the preceding paragraph apply. Where large changes in plant are taking place or where it is desired to extend the period before another complete study is made, methods e and f of Paragraph 3 involving partial re-estimates or recalculation are more appropriate. This is particularly true for larger utilities or for individual account exceeding $100,000 of plant.

Period Between Complete Studies

7. Depreciation charges even in the simplest project should be re-examined from time to time. It is obvious that, until final retirement, those charges involve estimates of future life and salvage. This is particularly true under group accounting where average and weighted values are used. The remaining life method requires reappraisals and reviews of the estimates used from time to time. Complete study of the basic data and new determinations of estimates should be made for each account at intervals depending upon the occurrence of changes in conditions which suggest change of characteristics of the account. Thus, wherever large additions or large retirements have been made, new studies in the subsequent year are indicated.

 

Recommended Maximum Interval Between Studies

Where Accrual in Intervening Years is Determined Each Year by:

Accounts of over $100,000 of Plant

Accounts of $25,000 to $100,000 of Plant

Accounts of Less than $25,000 of Plant

Applying depreciation rates to new plant balances (Methods a., b., c., Paragraph 3)

2 years

3 years

4 years

Applying new age distribution data from derived survivor curves to give new remaining lives and applying this to new plant and reserve balances (Method e.)

4 years

5 years

5 years

Applying new judgment estimates of remaining lives to new plant and reserve balances (Method f.)

3 years

4 years

6 years

Annual Reviews and Schedules of Studies

8. Large utilities are, in general, required to review depreciation accruals annually and file with the Commission annual reports showing changes in estimates or rates which management feels should be made together with the resulting accruals. In connection with these reviews it is suggested that periodic studies of a number of accounts be made each year, according to a predetermined schedule, so that over a span of a few years detailed studies of the entire plant are made. Suggested material to include in the review reports is a follows:

9. Smaller utilities not filing annual review reports will more often combine their reviews with periodic studies of all accounts at one time. Such reviews should be made every three or four years, and in any event not longer than five years apart, depending on size and circumstances as indicated in paragraph 7 above. The results of these reviews shall be filed with the Commission.

CHAPTER 9

GENERAL CONSIDERATIONS AND STAFF PROCEDURES

Check List for the Staff Engineer

Examination of a Utility's Books

2. In undertaking a depreciation study, the books of the utility with respect to the plant accounts and the depreciation reserve should be inspected and checked to assure that reasonable procedures have been used in arriving at the current values. The historical origin of the initial entries either on formation of the company, on outside appraisals, or on prior actions by the Commission should be checked and the accumulations since that date reviewed. If doubt as to the correctness of the original entries or if evidence of arbitrary write-ups or write-downs appears, the matter should be reviewed with the possibility of requesting the Finance and Accounts Division to undertake an audit. In connection with the depreciation reserve account, check for possible transfers to or from surplus. Where it appears that the accounting requires corrections, the accrual determinations should be deferred until these corrections have been determined. Approval of the Director or Assistant Director of the Utilities Division should be obtained if an appraisal and reserve requirement study for purposes of restating the books is contemplated. In recommending such a procedure specific reasons for doing so should be stated. All efforts to utilize recorded book figures (with adjustment, if necessary) without appraisals should be explored.

Special Considerations for Smaller Utilities

3. As previously noted in Paragraph 12 of Chapter 4, utilities having generally less than $100,000 total plant may simplify the accrual determination by using composite values rather than attempting separate results by accounts. For these utilities it is essential that two minimum conditions be met. First, the accrual should be determined as described herein, and credited annually to the reserve. This may be based on judgment estimates for very small utilities applied as a single percent to gross plant. Second, the retirements of plant should be recorded and deducted from both the capital and the reserve accounts. The staff engineer in viewing the depreciation practices with utility representatives should stress these two essentials in preference to presenting too much detail with regard to the depreciation determinations itself. Good engineering judgment in selecting over-all estimates to arrive at a composite rate may be the only practicable means of determining consistent depreciation charges for very small utilities.

Depreciation Charged Through Clearing Accounts

4. In larger utilities it is common practice to charge depreciation on such items as vehicles and work equipment to a clearing account from which the portion assignable to construction and the portion assignable to maintenance is later determined. Where clearing accounts are used, the engineer must set out separately the depreciation accruals which are charged to clearing. These accruals are not part of the charges to the depreciation expense account.

Preparation of a Staff Report

5. In preparing the chapter on depreciation reserve and depreciation expenses for a standard results of operation report, certain pertinent items from the engineer's study should be included. The nature of the original entries should be recited and a tabulation of the historical growth of the depreciation reserve should be shown. A weighted average book depreciation reserve for the years under consideration should also be shown. This may be determined as the mean of the beginning- and end-of-year balances, or the mean of average monthly balances where these are available. The weighted average depreciation reserve is carried forward to the rate base chapter for the reserve deduction. The depreciation accruals as recorded for a recent year and determined for the current year should be shown. Where the company has not previously used the remaining life method, the following paragraph should be included:

A complete determination as prepared on standard forms D-1 or D-2 should also be included. Additional material which may be presented in larger company reports includes: A tabulation of company and staff estimates, a tabulation of the depreciation reserve by accounts as of a recent date, and a tabulation showing methods of allocations between divisions or departments. Further information in preparation of a report is contained in Standard Practices U-2 and U-3.

Analysis of Reasonableness of Results

6. In the final analysis, a determination of depreciation accruals is based on engineering judgment of anticipated future conditions. It is therefore well to apply some test of reasonableness to the final results. Normally the composite accrual rates for a company should fall somewhere in the range from 2% to 4%. Where a composite rate exceeding 4% develops, it may be well to check the estimates or to analyze company policies with regard to placement of new plant and retirement of old units. As a further test of the reasonableness, it is well to compare the results determined for rate-fixing purposes with those reported for income tax purposes. In particular, the depreciation reserve carried on the books as compared with the depreciation reserve carried for income tax purposes should be noted.

Depreciation for Income Tax Purposes

7. In computing the depreciation allowance for income tax purposes it is often feasible, particularly for small companies, to apply the same determination for both tax and rate fixing purposes. However, differences in such factors as use of beginning of year versus weighted average plant, charges for interest during construction, past credits and debits to reserves, and other factors may cause differences in the two determinations. For information regarding depreciation requirements for income tax purposes "Bulletin F" of the U.S. Treasury Department, Internal Revenue Service should be consulted.

Extraordinary Obsolescence

8. Occasionally instances of extraordinary obsolescence such as the unexpected early retirement of a major unit of property may require some form of an adjustment. When instances of this type arise, application of the remaining life method will often provide a reasonable accrual. If, however, in the opinion of the staff engineer, special consideration is required he should refer his recommendation in the matter to the Director or Assistant Director of the Utilities Division.

Standard Forms

9. To assist the staff engineers, standard forms have been prepared for recording data and calculating depreciation results. These forms as illustrated in this practice are as follows:

Form No.

Illustrated By

Subject

D-1

(not shown)

Annual Depreciation Accrual and Rate Determination (worksheet)

D-2

Tables 4A to 4E

Annual Depreciation Accrual and Rate Determination (form for typing)

D-3

Tables 5A and 5B

Remaining Life from a Survivor Curve

D-4

Table 5C

Elements of a Survivor Curve

D-5

Table 5D

Remaining Life from Accounting Records

D-6

Tables 7A and 7B

Determination of Salvage Values

CHAPTER 10

COMPANIES USING THE REMAINING LIFE METHOD

General

1. Most of the large utilities in California determine depreciation accruals using the remaining life method. It is being employed as standard practice in small company rate proceedings, at which time provision is made for continuing the accrual on this basis. Thus over a period of time it is anticipated that most small utilities will determine accruals on the straight-line remaining life basis.

Larger Utilities

2. All large electric, gas, telephone and water utilities in California, with the exception of one, now utilize the remaining lfie basis for book depreciation accruals, as follows:

California Electric Power Company

3. Agreements have generally been reached with the larger utilities setting forth details of introducing the remaining life method. Where decisions have required the remaining life method, agreements have usually been reached as a basis for such decision. It is not possible to include a typical agreement since conditions differed to some extent in each case.

4. In general, the above companies submit annual statements of their depreciation accruals. Twenty-two of these companies use the straight-line method. Three use the sinking fund method with various interest rates.

Smaller Utilities

5. In general, agreements as such have not been entered with the smaller companies. The staff engineer as standard practice in rate proceedings in the "Results of Operation Report" generally determines the recommended depreciation accrual on a remaining life basis for rate-fixing purposes. If such allowance is approved by the Commission and allowed in the new rate level, the Commission normally includes a provision in the order as indicated below. At the present time over 300 smaller utilities are using the straight-line remaining life method.

Typical Wording of Ordering Paragraphs

6. Where the remaining life depreciation method has been ordered by the Commission, typical ordering paragraphs have been substantially as follows:

* For small companies, periods ranging from three to five years depending on size and composition of plant are used.

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