Six-Month Update on Our Solar Panels


We installed our solar panels in March 2016, and they’ve done great! After six months of usage, I put together some numbers in case you’re interested in how they’ve performed. If you missed my initial solar panel post, you can read it here. This is a 7.0 kW, 28-panel system facing half east and half west.

Six-Month Summary
Here is a summary of our data from April through September, the half of the year when we get the most sun and use the most electricity due to the air conditioner.

Total Avg/Month
Solar Production 5343 kWh 891 kWh
Total Usage 7612 kWh 1269 kWh
Energy Sold Back to Power Company 2797 kWh 466 kWh
Energy Produced and Used 2546 kWh 424 kWh
Total Financial Benefit (at 10.8c/kWh) $577 $96.17

Monthly Data
The panels produced more than we used this spring, so we actually built up a nice credit with Green Mountain Energy for the first couple of months. Then as the temperatures rose and we started using the a/c, the panels couldn’t produce enough to keep up, so we started using up our credit and finally had to start paying for power again. Here are the details month by month:

Month Power Generated Power Used Effective Electric Bill Savings
April 800 kWh 489 kWh $-33.59 $86.40
May 837 kWh 812 kWh $-2.70 $90.40
June 994 kWh 1503 kWh $54.97 $107.35
July 1080 kWh 1623 kWh $58.64 $116.64
August 863 kWh 1768 kWh $97.94 $93.20
September 769 kWh 1417 kWh $69.98 $72.58

Estimated vs. Actual Production
Before installing our system, I used the Department of Energy’s PV Watts calculator to estimate our production. It was pretty accurate. So far we’re actually producing slightly more than expected, an average of 3.8 percent more during this period.

Time Period Estimated Production (kWh) Actual Production (kWh) Difference
April 815 800 (1.8%)
May 898 837 (6.8%)
June 927 994 7.2%
July 942 1080 14.6%
August 860 863 0.3%
September 705 769 9.1%
SIX-MONTH TOTAL 5147 5343 3.8%

We are very happy with how well the system is performing. It’s actually doing so well that we hope to add a pergola in our backyard and top it with additional solar panels to generate even more power. From October through March, we’ll largely stop using the air conditioner, so our monthly usage should drop to around 500-550 kWh. At the same time, we’ll obviously be getting less sun, so the savings from the panels won’t be quite as dramatic. I’ll try to post a full-year update in April 2017.

As always, if you would like any more information, just ask through my contact page.