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Generating my own electricity

Our new photovoltaic solar panels started generating electricity a month ago today. It was dusk on a cold February day when the system was all ready to go, so I was suprised to see the light flashing on the generation meter and the inverter showing that, even in such poor light, it was making a little bit of power.

The next day was even more exciting. Cold and crisp, with a bright sun, it was a perfect day for generating electricity. I even found myself sharing the generation figures on Twitter!

We’ve got a 2.1kWp array. That’s 12 Sharp panels on a steep (45 degree angle) roof over the garage. The front of the house faces south west, and we has solar thermal panels for hot water installed a few years ago. With those panels, and two dormer windows, there isn’t enough room to add PV panels.

I’d more or less given up on the idea, because there are a couple of big trees that shade the south east facing garage roof, so I didn’t think it was suitable. Until, that is, I talked about it with Stuart Houghton, director of much recommended installer Abacus Renewable Energy, and he offered to come and measure the potential of the site using a Solar Pathfinder gizmo. This predicts how much energy can be generated taking any shading into account.

It calculated that without shading, and with a better roof angle of 38 degrees, our system would generate 1,948 kWh a year. With the shading, that falls to a predicted 1,589 kWh. However, as the measurement was taken at the lowest part of the roof, and the panels have been installed rather higher up, Stuart is confident we will generate more that that.

The predictions are broken down by month. February’s is 83.31kWhs and March’s 133.84. To date we’ve generated a total of 96kWh, so it looks as if we’re on track. Things go up quickly as we go into spring and summer, as the shade only falls on the roof in the winter months.

I regularly add our meter readings to the imeasure site, both as a record of our usage, and to compare with others. It’s really satisfying to see the line on the graph that measures our electricity use – which is normally very stable – start to go down. So far that’s just because we’re using the power we’ve generated, rather than importing it.

The next challenge is to learn how to work with the system and get the most we possibly can out of it. The easy one is running the washing machine. We already prefer to do a wash on a sunny day, so it dries on the line. Now it makes sense to put the load in slightly later in the day, when the panels are generating at full tilt. I never need an excuse to put off Hoovering, although a sunny day isn’t going to be my preferred time! Working out how to get the best out of our solar thermal panels took a bit of trial and error. I think that getting the best out of the PV will be easier.

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