Energy Report, April 2010

We started producing green power on April 1, so this is our first full month of production from our solar electric system. We didn't use any electricity for space heating or water heating, as the solar heat collectors provided plenty of hot water for all our needs.

Statistics

Solar electricity produced: 717 kW h (23.9 kW h per day)
Electricity consumed: 279 kW h (9.3 kW h per day)

Discussion

For the month of April we produced 2.5 times as much electricity as we consumed, and we exported a net surplus of 438 kW h. We don't expect to maintain this ratio year-round, because we will consume more and produce less in the winter months. The solar energy production was 5% more than was predicted by the PV-Watts calculator for this month, so we're optimistic that we will reach its predicted yearly production of about 7000 kW h. Even if our consumption doubles during the 3 coldest months we should use considerably less than that.

On an average day our system produced 23.9 kW h of AC electricity delivered to the grid. The daily production varies quite a bit depending on the weather conditions. Here are two graphs showing our production on a very clear sunny day, and on a very cloudy and rainy day.

The DC rating of the solar panels is 6150 watts under "standard test conditions", which means brighter sun than we typically get in Michigan, and we lose about 5% in the inverters as well. So under typical conditions the system produces around 5000 watts under full sun at mid-day. But occasionally we have seen much higher power levels, on days with scattered clouds where the sun is not blocked by a cloud but additional light is reflected from clouds that appear near the sun. The result is a brief period of brighter-than-normal sunlight. Here's the inverter monitor showing 6623 watts during one such spike, which lasted only a minute or so but it was nice while it lasted!

 

 


This page was updated on Monday January 23, 2017