If you’re like most Americans, you’ve spent your life invisibly attached to an electric meter. When you wake up and switch on the light, you nudge it forward a little faster. When you toast bread, watch TV, open the fridge, flick on the computer, you push its pace. For all practical purposes, it only goes one way.

But in the last few years, a small but quickly growing band of Americans have found out that you can make the meter spin backward. These are not the off-the-grid, back-to-the-land, composting-privy sorts who pioneered the renewable energy movement in its early days. No, these are suburbanites (and city and small-town dwellers) who are installing photovoltaic (PV) systems on their roofs — systems that tie directly into the power grid. They buy power from the local utility, just like always. But when the sun comes out, they are the local utility, pulling electrons from the sun and pushing the extra out to the grid.

Christian Grieco, for instance. IT consultant for a cable TV company. Lives in a cookie-cutter suburb of Albany, New York — that’s him in the two-story colonial with the quarter-acre lot. And the 24 panels on the roof. He explains, “I called my neighbor over and said: ‘You see it spinning backwards? My electricity is going into your refrigerator.’”

I know how he feels, because we put 12 of these panels up on our roof last spring. Now, when friends come to visit, they are forced to ritually admire the new system, much as we once permitted them the pleasure of viewing, say, our infant’s new tooth. A stop by the electric meter to see it performing its trick is now de rigueur on sunny days.

Ten years ago, such a scene was all but impossible. For one thing, the local utility wouldn’t allow it — partly because it was a hassle for them, and partly because it was a danger to line repair crews. So the key invention was a simple and reliable “inverter” — mine is a little red box in the basement, a “Sunny Boy” model, built in Germany. It translates the electric conversation between my rooftop, which is now a 2-kilowatt power plant, and the rest of the grid; there’s a device performing much the same function at nuclear reactors and coal-fired power plants and hydro stations and all my brother providers. If I produce more power than I use in a given month, I get a credit. Most months, my electric bill just gets substantially smaller.

Which brings us to the other reason this didn’t happen a decade ago: The economics didn’t make sense. Though the sun provides energy for free, the cost of the panels and other gear was so high that solar couldn’t begin to compete with grid power. In a sense, it still can’t — solar energy in this country costs consumers something like a quarter per kilowatt-hour, compared with something like a nickel for conventional fossil fuel. But that’s starting to change. Not because regular electricity is getting a lot more expensive; with its abundant coal America can generate cheap power for a very long time. But because — sporadically, haltingly, and over the objections of the federal government — America is beginning to realize that the real cost of cheap energy is considerably higher. That burning coal means polluted air, sick kids, global warming. And so, in a few key places, government is beginning to tilt the balance. If you put in a solar system in New Jersey, the state will cover as much as 70 percent of the cost. In California and in New York, about half. A scattering of other states — including Arizona, Vermont, and Massachusetts — offer similar subsidies.

The pressure for such programs is increasing as the news about climate change becomes more urgent — in August, a study in Science reported that solar technology was developed enough to play a major role in fending off global warming, but only if we increased its use 700-fold in the next half-century. That sounds impossible — but it’s only a 14 percent annual increase, less than half the current global rate. “It was about three years ago that solar started to go into an overdrive growth rate worldwide,” says Christopher Flavin, director of the Worldwatch Institute, a Washington environmental monitoring group. More solar power has been harnessed on the world’s rooftops in the last two years than in all of previous history. And now Americans are stepping up to the plate in rapidly increasing numbers. One solar panel manufacturer calculates that the domestic PV market is growing as fast as 60 percent a year, fast enough that within a decade, California alone should have more solar panels than any single nation. “The global installed capacity will hit a gigawatt this year,” says Randy Udall, head of the solar program in Aspen, Colorado, one of the nation’s most advanced solar cities. On the one hand, that’s barely more than two big coal-fired power plants. Still, it’s enough to encourage an industry: The world spent $20.3 billion on development of solar and wind power in 2003, one-sixth of the total global investment in power-generation equipment. Notes Udall, “This is not a children’s crusade any more.”

The subsidy for renewable energy doesn’t come close to matching the billions in government support for fossil fuels, which includes everything from the oil-depletion allowance to the endless federal largesse for “clean coal” research. Still, the government help, almost all of it from states instead of the federal government, is crucial. “Absent that, I couldn’t have done it,” says Grieco, who took advantage of New York’s law to cut his costs in half. “I didn’t have $31,000, but I did have $15,000.” At that rate, he’ll have a 20-year payback on his investment, and the panels should last another 20 years after that.

Dori Wolfe’s company, Global Resource Options, installs systems across the Northeast. They did $1.3 million in sales last year. This year, thanks to the rebate laws, they were closing in on $3 million by September. Some states, like Vermont, consistently max out the government funding pool — “as soon as a customer commits,” says Wolfe, “I get the paperwork to the state capitol so they don’t miss out.”

In a perfect world, people would buy clean power even without subsidies, simply because they wanted to help clean the atmosphere. But, as Udall points out, much as Thomas Jefferson mystifyingly managed to overlook the fact that he owned slaves, we now collectively overlook our production of 45,000 pounds of greenhouse gases per family per year — enough to fill two Goodyear blimps. Surely our descendants will wonder why we didn’t notice, why we did nothing.