Second Year Performance Review

Monthly Solar Production 2019

Time to run the numbers again: let’s check out the performance of our solar system during year two. In 2019 we produced 6,764 kWh of power, about 7% less than 2018. Spring and Fall were noticeably grayer in 2019, which likely accounts for the drop. We consumed 2,300 kWh of the power we generated on premises and fed the other 4,464 kWh of excess power production to the grid for others to use.

At the 2019 utility rate of 15.33 cents per kWh, we saved $1,036.92 on our utility bills in 2019. Combine that with 2018 savings and after two years we’ve recouped 14% of our investment.  At the current rate in 12 more years we’ll have saved as much as we spent on the system. But of course the utility rates will rise during that time so we’re probably looking at 10 years or possibly less, depending on the rates.

July was the biggest month in terms of power generated in 2019, compared to May in 2019 (as I said earlier, gray wet spring). March was also a big month last year, which makes sense given the bare trees (one of our strings is partially shaded by oak trees in the morning) and the cold weather, which noticeably boosts panel efficiency. March is also the month when the sun’s angle is optimal for our 45 degree panel orientation.

So far, so good. Here’s to a sunny spring this year.

First Year – Results

solar power generation by month 2018

It’s now been a full year since we installed solar at the house–time to look at the numbers and see how things went in terms of production and return on investment. While planning back in the summer and fall of 2017, we calculated our estimated production using the PV Watts calculator at the National Renewable Energy Lab. Turns out it was pretty accurate on the whole: 7,705 kWh for the  year, versus actual production of 7,250 kWh.

We used 2,418 kWh of that power ourselves, offsetting power we otherwise would’ve had to buy, and pushed 4,832 kWh onto the grid for other people to use. At the current rate of 15.59 cents per kWh, that saved us $1,139.26 in 2018, a return of 7% of our investment.  In short, the system performed very much as expected.

It was interesting to see the variability in power production month to month. May was the biggest month overall, but we had an usually dry and sunny May here. One surprise was that December ended up being a bigger month than November, January, and February, which is surprising given the short days and low sun angle. But we had a lot of sunny days in December, and the cold temperatures help the panels work efficiency.

Here’s to an even better year in 2019!

 

Six Months In: Results so Far

net metering

Last month marked the half year point since our solar system went online, so I thought I’d take a moment to share some numbers and report on how things have gone in general. All in all, we couldn’t be happier–the only significant issue is that our utility company, Central Maine Power, is going through a complete billing system meltdown. Let’s just say I’m glad I keep careful records of our power usage, because they sure don’t! Continue reading “Six Months In: Results so Far”