Nick Canzoneri weighed several factors when he went shopping for a new flat-screen TV at the Best Buy in Gaithersburg, Md., a few days ago. He wanted the right brand ("Sony. I've had one for 20 years. I tend to stick with what I like ") and the right price. Size mattered, too. Canzoneri's son talked him into the enormous 52-inch model he ended up trying to wedge into his Toyota sedan.

Suffice to say, environmental considerations weren't at the top of Canzoneri's list.

Soon, they might be.

Those big, bright flat-panel TVs suck down far more power than the puny cathode-ray tube TVs they're rapidly replacing. Which is why regulators and environmentalists — who usually reserve their passion for shrinking rain forests, melting glaciers and gas-guzzling SUVs — are turning their attention to the once-humble TV set.

Last week, after two years of debate and study, California became the first state to challenge America's love affair with its TV set. A state panel established the nation's first energy-consumption limits for TVs up to 58 inches wide. Regulations for larger sets will be phased in later. The new rules do not affect TVs for sale now, but will require TVs sold in California to use about a third less power by 2011 and about half as much by 2013. TVs that can't meet the standards would be banned from sale in California, which accounts for 10 percent of the 35 million new TVs sold in America every year.

The prospect of the government messing with its citizens' God-given right to a super-size TV turned what might have been a mundane regulatory proceeding into a shot heard around the world. At least three other states (Washington, Oregon and Massachusetts) and two national governments (Canada and Australia) said they, too, will consider energy limits.

Television has long been accused of being a cultural polluter, but the California Energy Commission's move touched off debate about how much our national TV habit has contributed to fouling the physical environment as well.

The energy commission estimated that TVs account for 10 percent of household electrical use in California, once "related devices" like digital recorders and game consoles are included. But the Consumer Electronics Association, which opposed the new rules, says that figure is misleading since it covers all of a household's electronic devices, from iPods to computers. The Arlington-based trade group estimates that the TV alone accounts for no more than 3 percent of a household's monthly power bill.

Further, the group warns that the new regulations could raise prices, limit consumer choice and stifle innovation not just in California, but nationwide, as manufacturers redesign their products to comply with the state's new law. The most vulnerable may be power-hungry big-screen models, sets that use the less efficient plasma technology, and a new generation of TVs that offer a 3-D picture or combine the functions of a TV and a personal computer.

"It's not this generation of TVs that you have to be concerned about, it's the multi-function TVs of tomorrow," says Jason Oxman, a vice president at the Consumer Electronics Association.

The new regulations include technical requirements that could prompt a costly overhaul in TV designs, says Jon Fairhurst, a manager at Sharp Labs, the U.S.-based research arm of the Japanese set manufacturer. To save power, he says, new TVs would have to turn off automatically if attached to a DVD player that is turned off, something no TV does now.

State officials and environmentalists say it's about time that TVs follow other appliances whose energy use is regulated, from air conditioners to water heat-ers. Powering down the set will not only save users money (roughly $31 per household annually, according to the state), it will eliminate tons of greenhouse gases that power plants otherwise would generate.

Without the regulation, the state would need to build a $3 billion power plant to keep up with demand, the state commission says.

"Whether it's refrigerators or TV sets, anytime anyone has proposed regulation, the rallying cry is always the same: 'This will stifle innovation,' " says Noah Horo-witz, senior scientist of the Natural Resources Defense Council environmental group. "Well, refrigerators are far bigger today, they have more features, and they use one-quarter of the power they did 25 years ago."

Hundreds of TVs already comply with the 2011 and 2013 standards, says Horo-witz, and sensors that automatically adjust brightness and contrast based on ambient light would add little to the cost of a new set, he says.

Vizio, a leading HDTV manufacturer based in Irvine, Calif., will have no trouble complying with the standards by 2011, says co-founder Ken Lowe. "If little old Vizio can do it, I'm sure the bigger guys can do it, too," he says.