November 20, 2009
by Paul Gipe
Most contracts for solar PV, such as those under Ontario's Standard Offer Contract program and its new Feed-in Tariff program, are written in terms of AC kilowatts (kWAC).
However, the solar industry, especially the manufacturers of solar PV panels, refer to its technology in kWDC. This is in part historical, as early solar panels were used exclusively in remote DC systems, and in part because the solar panels themselves produce DC.
Most statistics on the industry refer to the raw amount of solar power installed in kWDC or MWDC. There are exceptions of course. California, for example, only reports kWAC installed.
Two 10-MWAC projects in Ontario are equivalent to the industry's standard notation of 23.5 MWDC.
This can be extremely confusing--to put it mildly.
California assumes that there is about 15% of a kWDC are lost in the conversion to a kWAC. Thus a solar PV kWAC is about 85% of a solar PV kWDC.
Conversely, a 10 MW solar PV plant is equivalent to about 11.76 MWDC. Thus two 10-MWAC projects in Ontario are equivalent to the industry's standard notation of 23 MWDC.