Peak Solar!


This time of year, around the summer solstice, is the annual peak for solar energy around here! I have just a few DIY panels on the roof and side of my house – cost me a couple of thousand dollars five years ago. There are too many shady trees in my leafy exurbia to make a full professional installation worthwhile. The four 150-watt panels I bolted down to the roof face east instead of south and only get about four or five hours of direct sun even during the longish days of late June. With luck I average about 300 watts of actual output from my solar roof for about five hours — about 1.5 kilowatt-hours per day.

Not much by home solar standards — my peak solar production is less than a tenth of the annual average solar energy of a typical home installation.  

But it also cost me less than a tenth of what a professional installation would. The panels charge a 12 volt battery bank, which is connected to an inverter that is usually switched on to cover the house circuit with my refrigerator. The system is not grid tied — either the house circuit is running off the panels and batteries, or it is running off the utility grid.  I have no way to return excess solar power to the grid — that would require a professional installation. But the advantage is that I have backup power in case of a blackout. Two more panels on the south side of the house charge another battery bank and inverter that power a couple of floor lamps and the fan for the wood stove.

Most of the year this DIY system produces enough to keep the fridge running totally off solar power.  If it’s a sunny day, this time of year, there’s enough extra juice to charge my electric motorcycle — three days of surplus sun is about enough for one round trip to work.

Works out about right.  Of course, I have downsized the fridge — more on that later.


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