The falacy of solar power

That title is a bit inflammatory. It should be "The falacy of solar power on grid-tied homes." Instead of putting solar panels on your roof, here's why you should invest that money elsewhere."

I'm a big green geek, so I've always been drawn to solar power. Now as I am planning to build a new home for my family, I am asking if I should incorporate solar power in to my plans. I have come to the conclusion that putting photovoltaic panels on your roof is almost always a bad idea. Bummer. Read on to see why I think that, and what I think should be done instead.

First, some context. I'm talking about common single-family houses in North America, connected to the electrical grid, where the power company is required to do net metering.

Net metering means that any power you produce in excess of your consumption is sold back to the power company. The nice thing about this program is that you don't have to bother with batteries and charge controllers and transfer switches. That's a lot less equipment, a lot less complexity, a lot less cost. The big items are then the PV panels and an inverter. Any extra power you produce is pushed out in to the grid, and then consumed by someone else in the system. Similarly, any power you consume that you don't produce is pulled from the grid.

With net metering in place, the power you produce isn't really for you to use. Your PV array is just another producer on the electrical grid, while your house is just another consumer. It doesn't matter when you produce, when you consume, or how much. The difference is just settled in dollars.

It doesn't really matter where your PV array is, either. You can move your solar panels + inverter to a location with ideal characteristics - lots of sun. But why limit yourself to just your house roof vs. shed roof vs. a dedicated pole on the ground? Why not your neighbor's house, if it has good sun all day long?

I live in Western Washington, which is known for being overcast a lot of the time. Why not put a solar array up in Eastern washington?

Being close to the equator would improve the output of the panels, so why not put an array in New Mexico?

According to the Department of Energy, Californians pay about twice as much as me for their power. They also have more sun. So why not put up panels in California, sell the power there at $0.15 / Kwh, and use that money to buy my cheap Washington power ($0.08 / Kwh)?

I can also aim for locations that produce their power in ways that pollute. If my power is from water but yours is from coal, better to put my solar panels in your area than in mine.

Producing power at home is quite personal, but producing it at a remote location is different. It would make sense to buy an acre of desert in California and invite people to erect their solar panels there, for a small fee. Or find investors and cover the area with solar, for a return on investment. Bigger systems benefit from economies of scale. Wholesale prices on PV panels and inverters are just the start. Solar/steam/turbines, with a large array of solar-tracking mirrors that superheat water to drive a turbine is pretty attractive, but only at a large scale.

Surely this is better financially than doing it under gray Seattle skies, 1 house at a time, right?

In fact, the power company here (Puget Sound Energy) offerers a "Green Power Program", where I pay a little more for my power (about a penny per Kwh) to do something similar. The money goes to pay for renewable energy production, but you can't really track dollars or Kwh very closely. It's way cheaper than installing a solar array on my roof, though.

So, while photovoltaic panels may be a great technology to invest in, it seems like there are lots of reasons that the roof of your house is not the ideal place to put that equipment.

So, when does solar at home make sense?

First, solar house design. In my climate, that means windows to the south and thermal mass to match, along with plenty of insulation and reducing air leaks.

Second, solar hot water is interesting. No complex electronics or batteries, and it only works close by, so no producing hot water in Arizona to use in Washington. There are plenty of downsides that I won't go in to here.

Third, when off-grid, local solar power can be part of the picture. But this is a lot more expensive and complex than a grid-tied system, and you probably still want a generator for backup when it's not sunny. Again, lots of complexity that I won't go in to here. RV and boat people have this pretty well figured out - go talk to them.