US: EIA to begin including small-scale solar output in new data

The power generated by small-scale distributed PV systems in the U.S. will be included in the electricity data gathered and published by the Energy Information Administration (EIA) for the first time, beginning in December.

The Department of Energy’s EIA had hitherto omitted such data from its harvesting of electrical output, based on the increasingly inaccurate presumption that the sector was simply too small to pay too much attention to.

However, as the growth of small-scale distributed PV in both the residential and commercial rooftop sectors has accelerated these past few years, the EIA will now include monthly estimates of capacity and generation by state and sector in its Electric Power Monthly.

Previously, the EIA restricted its estimates of small-scale PV to its Annual Energy Outlook, overlooking monthly state-level estimates that could be integrated with EIA data gathered on utility-scale solar PV.

The EIA defines small-scale solar as PV installation with a capacity lower than 1 MW, which accounts for nearly all rooftop arrays installed nationwide across the U.S. This distributed, behind-the-meter source of electricity supply accounted for 33% of all solar generation in the U.S. in September, the EIA said. Combined with utility-scale PV and solar thermal, solar accounted for 1% of the total reported electricity generation from all “utility-scale sources” (but including small-scale PV) that month.

A large percentage – 40% – of the distributed solar electricity produced in the U.S. is located in California, with EIA data revealing that the state produced 3,057 MW (ac) of small-scale solar electricity in September, followed by New Jersey on 793 MW (ac) and Arizona on 609 MW (ac).

The EIA only estimates the amount of solar PV capacity produced because electric utilities do not necessarily know how much electricity is generated by rooftop PV systems. Instead, the EIA collects information on the number of systems installed in each state, and with the aggregrate capacity of each system calculates the estimate.

Utilities and third-party owners – such as solar leasing providers like SolarCity and Sunrun – have been providing EIA with the data in order to ensure greater accuracy when estimating and reporting just how much solar capacity the U.S. currently has installed, from the smallest 5 kW system right up to the giant solar farms of the Nevadan and Californian deserts.