My neighbor has a 9.8 kW solar system that has been in place for at least 5 years, maybe as long as 8 years. Here in the Silicon Valley summer, it is sunny and hot in the afternoons, but cools off at night and stays cool until late morning or early afternoon. The air conditioning load is low after 8 or 9 PM and does not pick up until noon.

His roof surface faces about 30 degrees south of west, and he therefore does not generate full power all day. Production is low during the early part of the day, but continues until the sun is close to setting. Production is lower in the winter because of the sun angle, but I don’t know by how much.

When his hot water heater had to be replaced, he switched from gas to electric. Last time I asked, he was not going to replace his gas furnace with electric, so the house is heated with gas and heating costs are not part of the electric bill.

Because of the daily A/C cycle and the elimination of space heating from the electrical load, his electric bill is essentially zero. On average, he is sending more power into the grid than he is consuming.

At the time he installed his system, the cost and the rebates were both a lot higher. He financed the system with a HELOC. Don’t know how much he borrowed or what the payments are, but I think he spent around $30,000 net. I suspect the HELOC payments might have been similar to the electric bill. The installation contractor was back repairing problems several times the first year, and this spring a number of panels died and had to be replaced. I have no idea what that cost was or who paid, as he said the panels were defective.

With net metering, no heating load, and the electrical usage pattern here, his is close to an ideal set up for solar. I don’t think you can replicate his results.

First, your A/C load is full time during the summer months. There is no time that the A/C is not running from late May through early October. Second, if your home was built in the 70′s or 80′s, chances are you have electric heat. Even if your panels face south, there are fewer hours of sunlight in the winter. You use less heat than we do, but it’s inefficient electrical resistance heating. I don’t see how you could on average put more power into the grid than you consume, unless you covered your roof with panels and doubled my neighbor’s output.

I would love to see the projections the solar sales people used in their calculations. The graph of production vs. usage would be especially informative, if they included that in their presentation.