The double stud framing of a Habitat for Humanity ZEH in Colorado allows for energy efficiency.

Photo courtesy of NREL

Economics of Zero-energy Homes

Cutting down on carbon emissions is a big deal. The polar bears can attest to that. So can drought-ridden villages in rural areas around the globe. But there are other concerns, too. First, there's the money factor.

Zero-energy homes run the gamut in price. A ZEH built in Frisco, Texas, in 2004 was listed at $1 million; a ZEH constructed in Edmond, Okla., in 2005 had an estimated retail cost of $200,000 [source: Oliver].

Regardless of price range, building a zero-energy home does cost more than building a traditional home of the same size and features. Estimates put the increase at anywhere from 20 percent to 60 percent [sources: ToolBase, Oliver]. It's a pretty big increase, but that can go down considerably when you factor in any available federal and state energy-efficiency rebates.

And then there's the whole $0 energy bill thing. A regular single-family home in the United States pays about $2,200 a year on power [source: EnergyStar]. Reducing that to nothing can save $22,000 over 10 years. If you factor in those government incentives, energy-savings might be able to make up for an increase in purchase price.

There's a wrinkle in the energy-savings estimate, though. A ZEH is only ZE if the people who live in it practice good energy habits. If the homeowners leave the lights on all the time, run the AC at 60 degrees F (16 degrees C) in summer and take daily 30 minute showers, the actual energy use of the home is probably going to exceed its generating capacity. In that case, the energy bill is going to be greater than zero.

In the end, the true energy-efficiency of a zero-energy home depends a lot on the people maintaining it. PV systems require regular checkups to work at their maximum efficiency. Even the highest efficiency air-conditioning setup is going to have to work overtime if people leave the door open in the middle of summer. But if the home is used as prescribed, it could potentially work out to provide substantial benefits -- both to homeowners and to polar bears.

For more information on zero-energy homes and related topics, look over the links on the next page.