Terms & Concepts
Calculating utility bills and modeling energy profiles can be complicated. This section explains some of the more confusing topics to make working with the PowerBill API easier.
The PowerBill API takes into account all the intricacies of the many styles of solar metering, including traditional net metering, Value of Solar Tariffs (VOSTs), Feed in Tariffs (FITs) and everything in between.
- Accounting Units - Net metering can be accounted for with units of currency (dollars) or units of energy (kWh).
- True-up Frequency - The frequency in which units accrued from net metering (dollars or energy) reset to zero and excess units are converted to actual payments. True-up frequency can be monthly (or by billing period), annually or perennially (i.e., carried over from one billing cycle to another indefinitely).
- Net Surplus Compensation (NSC) - Payment customers receive for excess generation at the end of the true-up period. NSC is typically valued at the avoided cost of energy (around $0.04/kWh). Some utilities do not compensate for excess generation. NSC for a true-up period (this could be annual or monthly) is calculated as total production minus total consumption multiplied by the NSC rate. When total consumption exceeds total production, NSC is $0.
FITs pay the customer for all the electricity generated by the solar system at a certain rate for a specified number of years. FITs are handled as incentives in PowerBill, and a credit will show under the incentives section of the results each year the FIT is valid.
Time of use (TOU) rates charge customers different rates for energy used at specified times of the day (TouPeriods). For example, a customer might be charged $0.05/kWh for electricity used during the middle of the night (Off-Peak), and $0.15/kWh for energy used during the middle of the day (On-Peak).