The antique-style lamps that are fast becoming a design necessity for retro bars, hip restaurants and chic homes from New York to London are helping to save the Earth—and keep people buying.

The old-fashioned bulbs, which look like the inefficient incandescent technology patented by Thomas Edison in 1878, could encourage people to change their lightbulbs more than once a decade, even as the world moves to greener lamps.

By rearranging LED chips onto a strip inside the bulb instead of in a clump, bulb makers found they can satisfy the innate human desire for warmer, natural light, which the first generation of LED bulbs failed to offer.

“People are looking for that sparkle and the cozy and warm effect that you see in incandescent bulbs,” said Kristof Vermeersch, head of global product management of LED spots at Philips Lighting NV.

Shifting fashions in lighting could help drive sales of LED bulbs that would otherwise need to be replaced every 10 to 15 years, because they’re so much more efficient than incandescent bulbs that need to be replaced a few times a year.

“The real problem of LED lighting is that the bulbs last for ages, so they don’t have these replacement cycles where the market just carries on making money,” said Tom Rowlands-Rees, an analyst at Bloomberg New Energy Finance. Now the industry has found a way to make people pay more for lighting because it’s cool, “not because they need it,” he said.

When filament LED technology was first demonstrated, by Japanese company Ushio Inc. in 2008, it wasn’t an immediate hit. Sales started to take off in the past two years, however, as the design was improved, prices fell and larger manufacturers from Philips to GE Lighting started making them, too.

“When LED first came out, it looked like alien material,” said Justin Wang, chief executive officer of AXP Technology Inc., the California company that introduced filament LED in the U.S. “But when filament LED came out, it looked like a familiar incandescent bulb.”

Just four years ago, the market for filament LED was tiny, and mainly focused in a few northern European countries. Now shipments are growing rapidly, and the market could be valued at $20 billion globally by 2020, calculated Wang, using LEDinside and TrendForce Corp. shipment and pricing forecasts.

Filament LEDs could also solve a problem for policy makers who have long desired to ban inefficient incandescent bulbs, over the objections of consumers who prefer the old-style look. Almost a third of British people who voted to leave the European Union in 2016 said they wanted to see the return of the old bulbs that were banned by Brussels bureaucrats, according to a YouGov poll. Even Donald Trump wrongly warned in 2012 on Twitter that energy-saving bulbs can cause cancer because of the miniscule amounts of ultraviolet rays they give out.

With better aesthetics, filament LEDs could help speed the switch from the 7 billion incandescent lamps still lighting the planet. Lighting demand is expected to rise 50 percent in the next two decades as poorer countries gain more access to power, according to the United Nations. Switching to LEDs could offset some of that increase, avoiding the release of more than 390 million metric tons of carbon dioxide a year.

It’s still difficult for consumers to tell the difference between an incandescent bulb and a filament LED, and manufacturers like GE say they need to do more to promote the benefits of this growing market.

“LED has been a tricky sell because you have to teach consumers and retailers about the technology,” said Matt Sommers, consumer innovation manager at GE Lighting. “We can’t just assume that they can look at it and know what it is.”