Now that 2020 is over, we can report annual results from our home’s solar panels. Previous posts can be found at this link.
Panel production data is accessible via a phone app or the computer. Charts for monthly and daily production can be generated. Records from our electric utility show our home averages 400 kW-hr of energy per month to operate all the electrical devices, based on 15 yrs of data. Our panel output nearly reached that amount in the summer months thus offsetting our house needs. Winter months production was low due to low sun angle and more cloudy days.
Viewed on a daily output basis, variability is obvious due to seasonal and weather differences.
Best performance came on 8 May 2020, a cloudless low-humidity day. Add to that the fact the Sun was shining almost perpendicular to the face of the panels. They delivered almost 20 kW-hr of electric energy (area under the curve). Our house typically needs less than 10 kW-hr in a day during May. The flat top on the curve shows they were at maximum power output for a few hours at over 2.5 kW.
We have records for 15 years of electric energy usage for our house prior to panel installation. The average monthly amounts in kW-hr are plotted below by the dark line. The winter months are highest due to the furnace motor and lights. The spring and fall months are lowest. There is rise in usage in the summer due to AC. The usage for 2020 is plotted in orange when solar panels were involved.
We’ve been asked how long is the payback time. It is hard to say with so little performance so far. Each year will be different. We are glad to be able to reduce our carbon footprint on the Earth. A web site provided by the Environmental Protection Agency computes some equivalencies for the energy our panels have provided this year. In 2020 they produced about 2,824 kW-hr of electric energy. Most of that energy was for our home usage. On the brightest sunny days of summer, our extra energy went to the grid for others to use.