XII. Metering

Customer meters may have various uses in the context of the CSI. Currently, simple meters on residential and most small commercial sites installed for billing purposes measure net energy use by the customer and may "run backwards" if the energy produced by the solar installation exceeds energy use. These simple meters may be used where "net metering" is permitted. Time-based meters, also referred to as advanced metering infrastructure (AMI), are required to measure performance in the event the Commission adopts performance-based incentives. They may also facilitate rate setting for solar projects that recognizes the value of output during peak and off-peak periods. Vote Solar believes that time-of-use pricing could spur development substantially.

System performance metering permits the customer to determine the amount of energy produced by the solar installation and permits the customer to identify system problems requiring adjustments or repairs. The staff report comments that most solar systems already include an inverter with self-contained internal metering and display equipment. The report recommends the installation of such meters be a condition of incentives in the CSI program. The CEC would maintain a list of acceptable performance meters for this purpose.

We certainly understand the need for good metering in order to manage and monitor CSI installations and the CSI program generally. We are particularly interested in the benefits of meters that measure usage with some specificity. We are also interested in exploring a utility tariff that would have the utility pay for solar power on the basis of peak and off-peak deliveries, and one that recognizes the fixed costs of distribution. We will retain the metering requirements currently in place for SGIP solar projects and explore metering and production payment issues in greater detail in workshops to be conducted by Commission and CEC staff. Among the issues we hope to understand are:

1. What types of meters are appropriate and cost-effective for various types of installations?

2. What are the benefits and costs of interval metering compared to net metering?

3. Who should pay for new meters?

4. What are the ratemaking implications of developing a tariff that provides payments to solar installations on the basis of production periods?