electricity

Off-grid alternative energy homes typically rely on battery banks to store surplus power for use when the various generation devices aren't working at their strongest (i.e. solar panels in cloudy weather or at night, windmills when it isn't windy, micro-hydro when the water flow has dried up, etc). The battery most often used in these installations is called a deep-cycle battery, and is substantially different than the battery you would expect to find in an automobile.

There's an old truism that says "if you can't measure something then you can't fix it." This applies especially well to an off-grid renewable energy installation not only because there are so many components that have to be working in order for the whole system to work, but because the fail-state for many key components may not be immediately obvious UNLESS you're keeping a record of their performance over time.

I happen to live off the grid. I don't mean this in a tinfoil-hat, leave-no-data-trail, They-are-going-to-get-me kind of way. I mean it in a "the-electrical-grid-owned-by-PG&E-ends-two-miles-away-from-my-house" kind of way. This means that I've had to learn a lot about electricity, and energy conservation, and renewable energy, and balance of system, and much more since I moved here five years ago.