Year in Review 2016 - Solar

I created a few new charts this year to evaluate the performance of my solar panels in 2016. Overall they did about as well as expected, though production was a bit lower than last year. I guess I shouldn't have skipped a year of cleaning!

Looking at the monthly data it's clear that a couple worse than expected months mid-year dragged down the annual numbers. Several months actually did better than expected. The "Tigo (DC)" numbers represent the raw DC power coming from the panels, while the "eGauge (AC)" power is the output of the inverter that's fed into my home electrical wiring.

Here's the daily data for all of 2016, which shows quite a bit of variation. It's a noisy chart but the general trend in production isn't too hard to make out. The orange "Use" line represents the power I used, the blue "Solar" line is power that the panels produced, the red "grid" line is power that went through my City Light meter (positive = purchased, negative = sold), and the green "Estimate" line is what my solar installer predicted I'd produce.

Summing up the numbers into a running total makes for a cleaner chart. Solar production tracked the estimate for the year very closely.

2016 was my third full year with solar panels, so I thought I'd take a look at the year-over-year numbers too. As expected the daily numbers have significant variation. If anything it seems as though the estimate for July may be a bit high.

The cumulative chart shows the trends more clearly. My panels produced about 3180 kWh in 2016.

I also compared my electrical use from year to year. You can tell which days I did laundry (the dryer draws A LOT of power). The cumulative chart shows that I was able to continue my miserly ways in from 2015 to 2016 compared to 2014. I used just over 2000 kWh this year.

Last but not least, the grid numbers for the year. These are essentially the sum of the production and use numbers. I finished out the year with a surplus of 1160 kWh. Frustratingly, a change to Seattle City Lights net-metering program (to comply with Washington State law) means that this extra power is forfeited. This creates a perverse incentive for me to increase my electrical use, since that power is effectively free for me to use. To City Light's credit, the forfeited power is transferred to their "Utility Discount Program and/or Project Share Program that assists income-eligible customers."