How much solar photovoltaic (PV) power is generated in the United States? According to a new report, official government figures may be understating the total by as much as a third. That's a pretty big deal!
Here's the problem: the Energy Information Administration (EIA) and other energy agencies can easily gather data on electricity from big, utility-scale solar power plants that sell into wholesale markets. But it's much, much more difficult to get data about electricity from solar panels on the customer side of the meter. That means that rooftop solar power on homes and businesses gets overlooked and undercounted.
By how much? A new study by the Solar Energy Industries Association (SEIA) and kWh Analytics — drawing on data from the latest Solar Market Insight Report — finds that the gap is enormous. Some 9.2 gigawatts of customer-side solar capacity has been left out of official statistics. That's 45 percent of total solar PV:
The results are astonishing: we estimate that actual solar production is 50 percent higher than the previous best estimates of solar production. In the 12 months ending in March, solar energy systems in the U.S. generated 30.4 million megawatt-hours of electricity. EIA’s utility-only estimate for the same period is 20.2 million megawatt-hours.
These new numbers reveal, among other things, that three states — California, Arizona, and Hawaii — now get more than 5 percent of their total electricity from solar.
This is of more than academic interest. These estimates play a big role in policy. For instance, how well is the federal investment tax credit (ITC) working? If you ignore behind-the-meter solar, the ITC appears much more expensive than it is.
Or consider the EPA's Clean Power Plan, which relies on EIA numbers to develop its state-by-state renewable energy goals:
In EPA’s "Alternative Approach," one of two methods for establishing goals in the draft Clean Power Plan, this produced a target solar contribution of 8.7 million megawatt-hours in 2030 -- less than a third of actual U.S. solar generation will be in 2015.
If you don't know how much solar PV energy you're generating, it's hard to set sensible targets for future production.
And finally, the difficulty of measuring behind-the-meter solar PV is of great importance to utilities. Almost all utility investments are based on projections of future power supply and demand. If behind-the-meter solar is invisible to utilities, they will overestimate future demand and over-invest in power plants and infrastructure, needlessly raising rates.
All this points to the need for "smart grids," in which behind-the-meter energy technologies communicate with central grid operators, allowing them to do truly integrated resource planning. We can't plan power systems well until we have a better idea how much power we have to work with.