Despite being the lowest producing month of the year my numbers for December 2014 turned out to be really good compared to the installer's estimate. In fact, the DC production was 47% more than the estimate of 43 kWh at nearly 72 kWh. AC production was lower (63 kWh) due to DC-to-AC conversion losses. As expected my solar production wasn't enough to meet my usage needs for any day this month, though overall about 34% of my use was provided by the solar panels on my roof.