Nicholas and Loan Gatai used to cringe when they received power bills that routinely topped $200. Last September the Sacramento, Calif., couple moved into a new, 1,500-square-foot home in Premier Gardens, a subdivision of 95 "zero-energy homes" just outside town. Now they're actually eager to see their electric bills. The grand total over the 10 months they've lived in the three-bedroom, stucco-and-stone house: $75. For the past two months they haven't paid a cent.

Almost unknown outside California, ZEH communities are the leading edge of technologies that might someday create houses that produce as much energy as they consume. Premier Gardens, which opened last summer, is one of a half-dozen subdivisions in California where every home cuts power consumption by at least 50 percent, mostly by using low-power appliances and solar panels. Several more are under construction this year, including the first ZEH community for seniors.

Aside from the bright patch of solar modules on the roof, Premier Gardens looks like a community of conventional homes. But inside, it's clear why they save energy. "Spectrally selective" windows cut power bills by blocking solar heat in the summer and retaining indoor warmth in cold weather. Fluorescent bulbs throughout use two thirds the juice of incandescents. A suitcase-size tankless hot-water heater in the garage, powered by gas, saves energy by warming water only when the tap is turned on.

The rest of the energy savings comes from the solar units. Set flush with the roof tiles, the two-kilowatt photovoltaic panels unobtrusively turn the sun's rays into AC power with the help of an inverter in the garage. An LED readout shows the system's electrical output. Just looking at it can give owners a warm feeling. "When I pull into the garage, sometimes I just like to look at the Sunny Boy [inverter] to see how much power we've generated," says homeowner Kurt Gonzales, whose family bought a 2,200-square-foot house.

In ZEHs, the solar production doesn't just feed the home it serves. If the panels are generating more power than the home is using--when the house is empty during a sunny day--the excess flows into the utility's power grid. Gonzales and other residents are billed by "net metering": they pay for the amount of power they tap off the grid, less the kilowatts they feed into it. If a home generates more power in one month than it uses, the bill is zero.

That sounds like a bad deal for the power company, but it's not. The Sacramento Municipal Utility District's solar expert Mike Keesee says that's because solar homes produce the most power on the hot sunny afternoons when everyone rushes home to turn up the air conditioner. "It helps us lower usage at peak power times," says Keesee. "That lets us avoid building costly plants or buying expensive power at peak usage time."

What's not to like? Mostly the costs. The special features can add $25,000 or more to the purchase price of a house. (At Premier Gardens, the premium was $18,000.) Rebates and tax breaks bring the cost down, especially in California, but in many states ZEHs can be prohibitively expensive. California's Clarum Homes announced that it'll build nothing but ZEHs in-state but isn't so sure that's cost-effective in lower-subsidy states like Nevada. For the consumer, it's a matter of pay now for the hardware to save later on the utilities. Advocates say the features pay for themselves over seven to 12 years.

Cutting the added costs is the goal. The Department of Energy hopes by 2020 to reduce those costs to zero while building homes that use 70 percent less energy. The key is new research in solar-panel technologies. Meanwhile, in Premier Gardens, the zero-energy future has already arrived for the Gatais. But now the hot weather is here, Nicholas is resigned to cranking up the AC and living a little. "I'll need to pay something," he says. Or perhaps not.