I finally had a chance to sit down and go through my solar numbers for 2014 and they look pretty good! Over the course of the year I generated a sizable surplus of power, about 35% more than I used. The two charts below show my solar production, the power I purchased from (or sold to) Seattle City Light, and the power that I used. The chart on the left is a one month moving average while on the right are monthly totals. Negative "grid" numbers represent surplus power that I'm selling.
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Here's a look at the cumulative numbers for the year. The chart on the left is a running total for the year while the chart on the right shows the percent of the energy I used that was generated by my solar panels. The first day that the monthly moving average had a surplus of power was March 25, 2014. Soon after, on May 7, I started having a net surplus of power for the year (and consequently stopped paying an electric bill). August 16 was a particularly special day when I had generated as much power as I would need for the full year. Even if my solar panels had stopped working that day I still wouldn't have needed to pay for power for the rest of the year.
Financially the panels are doing a great job of paying for themselves. For the year, I used about $121 worth of electricity, but my net bill from City Light was about -$43.00. That's right, I generated enough power to have a credit on my bill for the year. The real workhorse, though, is the renewable energy credit from the state. For me this works out to about $1,740.64 for 2014, which works out to be a bit more than the monthly payment for the loan I took out to cover some of the panel cost. In total I'm making about $13 a month in profit (plus having a $0 electric bill).
For those interested in the numbers behind the charts:
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