A very small percentage of U.S. homes are off the electricity grid — far fewer, for example, than in Africa. That said, North American designers of off-grid homes often end up posting questions on GBA.
To help this subset of builders avoid common design errors, I’ll share what I’ve learned from living in an off-grid house for 42 years.
Off-grid homeowners have a much stricter energy budget than owners of grid-connected homes. This is due to simple economics: off-grid electricity is expensive — on the order of $0.50 to $1.00 per kWh.
Sure, photovoltaic (PV) modules are relatively cheap. But batteries and gas-powered generators (or propane-fired generators) are expensive, and those of us who live off the grid need batteries and generators — because the sun doesn’t always shine.
During certain seasons, off-grid homeowners are likely to have an energy surplus. In Vermont, for example, a 1-kW PV system that produces 48 kWh of electricity in the month of December will produce three times as much electricity (145 kWh) in the month of May. If weather forecasters predict three days of sunny weather in May or June, you can plug in extra hairdryers, do several loads of laundry, and vacuum the house. But during a snowstorm in the middle of December, you’ve got to be careful about energy use. That’s when you will be using your broom instead of your vacuum cleaner.
You can power your off-grid house with a micro-hydro system or a wind turbine if you want, but by far the most common way to generate off-grid electricity is with a PV system.
If you have a large lot, you probably want to install a ground-mounted PV array. If you live in a snowy region, ground-mounted arrays make snow removal easier than it would be for a roof-mounted array. (Off-grid…