At mid-summer we are seeing strong results from our solar panels. Previous posts can be found at this link.
Their best performance came on 8 May 2020. It was 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.
Net metering for April through June shows three quantities of electric energy each day. The top blue line is the house usage from the grid needed to operate all devices. The bottom red line is the panel production. The purple bars are the net metered amounts contributing to our utility bills. The net for that 3-month period was negative. The panels exceeded our house needs by 28 kW-hr.
The month of July included many days of air conditioner use. The panels performed well, but our house needs were higher.
We have 15 years of electric energy usage for our house. The average monthly amounts in kW-hr are plotted below by the dark line. The winter months are highest due to the furnace and lights. The spring and fall months are lowest. There is rise in usage in the summer due to AC. The usage this year is plotted in orange through the month of July.
We’ve been asked how long is the payback time. It is hard to say with so little performance so far. That isn’t why we installed them. We wanted to reduce our carbon footprint on the Earth. That is happening. We used a web site provided by the Environmental Protection Agency to compute some equivalencies for the energy our panels have provided so far this year. Year-to-date they have produced about 2000 kW-hr of electric energy for our usage and that of the grid.