One solution for off-the-grid living in Arizona.

Our little off-the-grid vacation place has solar power. It’s an extremely simple system that consists of two 120-watt (I think) solar panels mounted on the roof and four deep cycle batteries in a little cabinet. The panels are attached to the batteries with a charger. Whenever there’s sun — which is just about every day in Arizona — the solar panels charge the batteries. All we do to maintain them is make sure there’s enough distilled water in the battery cells.

The building has both AC and DC power. That’s a weird thing that we decided on when we first set up the place. It’s a very small place with just one room, a loft, and a bathroom alcove. There are very few electrical appliances, and they’re split between AC and DC. On the AC side is an iHome clock radio (the kind you can put an iPod in), a 700-watt microwave, and a 600-watt single cup coffee maker. There are also outlets that can power a small ShopVac or laptop. Everything else is powered by DC power: 9 small light fixtures, the water pump, and a ceiling fan. (Do you know how hard it was to find a DC ceiling fan?) There are round DC power outlets everywhere there’s a standard AC power outlet. The fridge, stove, water heater, and furnace are all propane gas.

Theoretically, we can run the whole place on DC power with gas. On very short stays, we don’t even bother with the fridge. But since the batteries are hooked up to a 2000-watt AC inverter, we usually turn on the inverter so we can use those AC appliances and outlets when we want to. We have a little meter that plugs into a DC outlet to monitor the amount of juice in the batteries. At night, the power level gets low, but never too low to run lights or watch a movie on a laptop with power connected. And, in the morning, even before dawn, there’s always enough power to run my coffee maker.

It’s a great system. It cost about $2K for Mike to design and install and it meets all of our limited needs. I’m certain that if we built a house up here with more conveniences, a system just three or four times the size — perhaps supplemented with a small wind generator — would easily meet those needs. After all, it’s cool enough up here that air conditioning is not required in the summer — especially if the house had an energy efficient design that kept the hot air out. And if the sun isn’t shining, the wind is probably blowing.

Today, while relaxing with a book, the radio suddenly died. I checked the little DC meter and saw that we had plenty of juice — 15.4 volts, in fact. That’s the highest I’ve ever seen it. I went out to check the inverter and found lights blinking on it. Consulting the manual revealed that we had too much power for the inverter to use. The system is designed to shut down when available power exceeds 15 volts.

Oddly enough, to get the AC power to work, I had to come inside and turn on a bunch of lights and the ceiling fan and run the pump for a while. In other words, I had to throw away excess power. Once I got stored power down to 14.8 volts, I went outside and turned the inverter back on. Everything worked fine.

Keep in mind that this is a very small system and there’s no tracking on those solar panels. The panels are fixed to the roof, pointing southwest. (Imagine how much power we’d pull in if the panels were set up to track the sun?) It was about 2:30 PM when the problem occurred; it’s now almost two hours later and the sun is lower, so I don’t think the problem will reoccur.

My point is this: Arizona is a perfect environment for solar power, especially for small to moderate use. There’s no reason why solar can’t be set up to at least supplement power coming into an on-the-grid home. And for an off-the-grid home with modest needs, it seems to be a perfect solution.

So why aren’t more homes built with solar as part of the standard builder package?