The Department of Energy, or DOE, announced Friday that it’s strengthening energy efficiency requirements for light bulbs in U.S. markets, in a move anticipated to save Americans $27 billion on their utility bills over 30 years. The DOE estimates that the new standards will prevent 70 million metric tons of carbon from being emitted over 30 years — equivalent to the annual emissions of 9 million homes.

According to the new rule, light bulbs sold or imported after 2028 must have an efficiency level of at least 120 lumens per watt, almost triple the current minimum standard. Under the new standard, a light bulb as bright as an old-school 60-watt incandescent bulb would require no more than 6.5 watts of electricity.

The federal government has already once strengthened its efficiency standards under the Biden administration. Last year, the classic Edison-style incandescent bulb was almost entirely phased out. (That rule, which set the current efficiency standard of 45 lumens per watt, actually predates Biden’s presidency and was initially scheduled by Congress to go into effect in 2020, but it was delayed by the Trump administration.)

By 2028, when the new standards kick in, the DOE predicts that some 98 percent of new bulbs sold in the U.S. will be LEDs.

The federal standards do not prescribe a particular kind of bulb for common household usage, but merely mandate minimum efficiency levels. And they only apply to new sales and imports; no one is required to replace the bulbs already in their homes.

Exemptions are carved out for certain types of bulbs, like oven lights, where LEDs are unsuitable because they don’t perform well under high heat.

Andrew deLaski, the executive director of the Appliance Standards Awareness Project, a coalition of energy efficiency proponents, said the trend toward greater efficiency has made a difference in the battle against global warming — especially since the widespread adoption of LEDs.

“What was a 60 watt light bulb now uses, say, 9 or 10 watts,” deLaski said. “That’s a big reduction in energy use, which means less fossil fuels being burned in power plants which leads to climate change. But even an efficient technology can get better.”

Those improvements are already on their way, as lighting manufacturers have been steadily increasing efficiency in light bulbs for years, driven by economic incentives as well as federal regulation. Lighting manufacturers weighed in on the new standard during the federal rulemaking process.

“The modern LED light bulb is a much better light bulb than the one you bought five years ago, way way better than the one you bought ten years ago, and in another universe than the CFL [ compact fluorescent lamp] that you can’t even buy anymore,” said deLaski.

The new federal standards effectively guarantee that these innovations are shared across the market, ensuring “that all the choices available in stores and from internet sellers are going to be LEDs that incorporate the latest efficiency technologies,” deLaski said.