This is a little complicated. Honestly, too complicated for a spreadsheet or for my limited mathematical abilities.
We have a moving target and two sets of numbers, one ending in December and the other in November. There are reportedly ~60,000 MW of wind turbines in the U.S. as of the end of 2012. Would someone care to estimate the actual capacity factor of these turbines? I would like to know approximately how much energy these turbines produced. Actual performance is usually estimated at 1/3 the nameplate capacity. In other words, 60,000 MW of turbines should produce 20,000 MW on average, which over 1 year adds up to 174,720 GWH (or "thousand megawatt hours" -- the EIA's preferred units). The number of wind turbines increases in spurts throughout the year as new turbines are installed and new wind farms are put on line. These MW quotes are for total number of installed turbines. Total power increases, though some old turbines are removed or upgraded. Output energy also increases. As follows: Year (start of year; January), total capacity MW, increase MW over previous year, energy from previous year in GWH (1000 MWH) 2013, 60,000 MW, 13,124 MW, 125,914 GWH 2012, 47,000 MW, 6,800 MW, 109,521 GWH 2011, 40,200 MW . . . In other words, in 2012, energy increased by 16,393 GWH. That was coming from more turbines than there were in 2011, but how many more? The numbers increased continuously, by a total of 19,924, but a turbine installed in October 2012 contributed practically nothing to the 2012 totals. You could say that the 60,000 MW of turbines should have produced 174,720 GWH in 2012, but they only produced 125,914 so the capacity is lower than claimed. But that is not true, because most of the 13,124 MW added that year was not there at the beginning. Would it be reasonable to say the average capacity in 2012 was halfway between 47,000 MW and 60,000 MW? 53,500 MW nameplate, or 17,833 MW with the fudge factor of 1/3? That would produce 155,789 GWH which is still considerably above the actual total of 125,914. Using that crude method of assuming the average was 53,500 nameplate, the capacity would be 27%, not 33%. - Jed
