January 2012 will go down in the history books. Is this climate change? I feel as though I have moved to Boulder CO. Sometimes it's been cold, but mostly it's almost balmy. Last November, December, January heating degree days (base 65F) were 584, 978, 1,086, for a total of 2,646. This year the values are 429, 685, 823, for a total of 1,937, or 73% of last year's heating demand. I haven't once needed to wear my neoprene overbooties when riding a bike.
At the same time, January was extraordinarily sunny. The online estimating software called PV Watts estimates that my system, if completely unshaded, would make 330, 318, and 366 kWh in November, December, and January. The actual numbers, which include the effects of shading, have been 413, 303, and 468. December clearly has the most shading from trees to the south, and it's closest to the estimate. November and January have been 25 and 28% over the estimate. We at South Mountain think that Sunpower may be correct when they claim their panels outperform others watt for watt, but this also must be more sunshine.
In January, last year we used 418 kWh in the heat pump and this year it was 277. In fact, we only consumed 30 kWh more than the PVs generated. So it's scary but darn enjoyable.