Solar Gets Its Due From Energy Number Crunchers

Solar is getting its due from the Energy Information Administration, which is now reporting customer-sited photovoltaic capacity, in addition to the utility-scale PV total.

Earlier this year we reported on research by Michael Mendelsohn, a market and policy impact analyst at the National Renewable Energy Lab in Colorado, that revealed that EIA reports on the state of U.S. energy production were missing not just some but the majority of solar energy generated.

EIA solar power estimate

image via Energy Information Administration

But the agency reported late last month a new estimate that attempts to include the under-1 megawatt systems it had been missing. The result isn’t a power generation figure like Mendelsohn came up with, but the EIA did arrive at a well-informed stab at the total grid-connected PV capacity in the country – 3,536 MW AC.

As the chart above shows, this breaks down as about 1,000 MW residential, 1,500 commercial and industrial, and 1,000 MW utility-scale. But even the EIA admits that these numbers are very likely on the low side – which is why they call their estimate a “lower bound.”

“It is important to emphasize that this estimate is a lower bound for total PV capacity, as there are likely PV installations that are not captured” on either the reporting forms filed by utility-scale power plants or those filed by retail electricity providers serving net metered generators.

In his calculation, Mendelsohn used numbers from the Solar Energy Industries Association to try to get at a figure that better captured U.S. solar power production. There were some complexities and hurdles in doing this, and he had to make some adjustments and assumptions. But even taking a very conservative route, Mendelsohn arrived at a production number of 4,958 gigawatt-hours for 2011 — about 2.6 times the EIA number of 1,800 GWh.

As for capacity, Mendelsohn had total solar capacity at 4,458, but that included 503 MW of concentrating solar power and used Solar Energy Industries Association numbers reported in DC. That’s the form of electricity produced by panels, and from 10 to 20 percent of it is lost when converted to AC for the grid. With all that taken into account, the EIA’s figures look to be right in the same ballpark as Mendelsohn.

Pete Danko is a writer and editor based in Portland, Oregon. His work has appeared in Breaking Energy, National Geographic's Energy Blog, The New York Times, San Francisco Chronicle and elsewhere.

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