From an interview with Clay Sterling by Michael Burke published in The Journal Times (Racine):

Q. What is an off-grid home, and how did you achieve that?

A. There’s no physical connection between the home’s electrical system and the utility. You have an on-site power generation system, so you are your own utility. In my case, the sources are both solar and wind electric.

You store that energy in a battery pack for immediate or later use. Generally, those are sized for about three days of no power input — and generally, in three days you’ll have some power input.

But there are times, like in November, December and March, when you’re not generating enough. So you have to back up the whole system with a gasoline generator.

Q. Are we talking about do-it-yourself or professionally installed solar projects?

A. Professionally installed. We train homeowners and DIY people, but now 60-70 percent of people who go through program are in the trades. The systems are also being manufactured in ways that speed up installation for electrical and plumbing shops that want to offer this work.

Q. Where can one install a useful solar system?

A. For solar electricity, you need no shading from at least 9 a.m. to 3 p.m. every day of the year, and the sun’s position changes. Sometimes a roof is a suitable place. Sometimes a backyard, on a pole or on the ground.

Solar hot water, on the other hand, is very forgiving. You can have a little shade throughout the day with little or no impact.

Q. What are the investment costs and payback times for solar electric?

A. Before you install anything, you have to address energy efficiency. A homeowner could reduce electrical loads by 30-50 percent with energy-efficient measures. For every dollar you spend on energy efficiency, you reduce system cost by $3-$5.

A 4-5 kilowatt photovoltaic system for an average home would cost about $40,000 today, complete. After doing energy-efficiency measures, it would cost about $28,000.

Using $40,000, Focus on Energy would give a 25 percent rebate. A federal tax credit would knock off another 30 percent, for a final cost of about $21,000.

You’re still looking at a long time to pay off this system. But you can assume that each year the cost of energy will rise and value of dollar will decline.

The $28,000 system would end up costing you $14,700.

Q. What about solar hot water costs?

A. About $7,000-10,000 for a system. After the rebate and tax credit, you might spend $4,725. It would connect to a traditional hot water heater but reduce the amount of energy needed to heat water. It would supply 50-75 percent of an average home’s water-heating needs, averaged over a whole year.