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.
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Click to enlarge
This month continued the trend I noticed in November with the bulk of my production occurring in the first half of the day. I may need to do some investigating to see if that's due to the correlation between lower production and lower conversion efficiency and the number of panels I have facing each direction.
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Click to enlarge
Supporting this hypothesis is the plot of energy by panel direction. The chart below is averaged by the number of panels, so the higher production of the east panels means that each panel is definitely generating more during the day than the panels facing west. It's particularly apparent at the end of the month. The scatter plot shows large vertical smears of color on these days, indicating a large variability in individual panel production.
The monthly totals reflect this trend as well, with a clear difference between the east-facing and west-facing panels (5,6, & 9-14 versus 1-4, 7, & 8). Panels 9-14 have the least obstructed view to the east.
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Click to enlarge
I'm omitting the usual month-to-month comparison charts from this post, but will be including them in another post (coming soon!) summarizing the full year of data for 2014.