BERLIN — The green future of German heating is a white box the size of a U.S. refrigerator. It also happens to use the same technology.

"A refrigerator takes the temperature from the food inside the fridge and then kind of blows it out," says Wolfgang Gründinger, chief spokesperson for the start-up Enpal, which sells heat pumps. "And a heat pump is just the other system, like the other way around."

Heat pumps use a fan to draw outdoor air, circulating it past tubes of chemical refrigerant to extract warmth from outside, blowing it indoors to heat a home. Gründinger stands in front of two of the machines propped up near a foosball table inside the company's buzzing Berlin office. "It's super silent and super efficient," he says, "You need one kilowatt-hour of electricity to produce four kilowatt-hours of heat."

This efficiency means the cost of electricity needed to power a heat pump is around a third cheaper than natural gas. The savings are even greater for those who run heat pumps from solar panels.

A new bill under consideration in Germany's parliament would ban gas boilers and make heat pumps the law of the land by next year. Heat pumps are not widely used elsewhere in Europe, aside from Scandinavia. In the U.S., heat pump demand and usage have risen considerably in recent years, partly thanks to subsidies and tax credits.

"People realize that gas is super expensive, that we are dependent on foreign countries when it comes to gas, and they can just make their electricity on their own rooftop and have their heat pump at home," Gründinger says.

Natural gas prices in Germany have soared due to sanctions the country has placed on Russia, which, before the war in Ukraine, supplied Germany with nearly half its supply. Germany's Green Party has come up with what it thinks is a solution to both high energy prices and a warming climate. The party, one of three in Germany's coalition government, has overseen the bill now under consideration that aims to do away with the country's gas and oil heating infrastructure for good.

"Heat pumps are the key technology," says Kassem Taher Saleh, a Green Party parliamentarian. "They are future-oriented, climate neutral and provide security. They are truly the only option for brand-new buildings."

An early summary of the bill, leaked to German media three months ago, revealed the Green Party's plan would be to require all new buildings in Germany to install heating systems that use at least 65% renewable energy, starting next year. The heat pump is currently one of the only ways to meet this goal. (Heat pump sales in Germany rose by more than 100% in the first quarter of 2023, but this had more to do with gas prices than the heat pump bill).

Early bill language also mandated that any building in Germany — including family homes — whose heating systems had broken down would be required to meet this goal, and it was this part of the proposed bill that sent German homeowners into a frenzy.

Taher Saleh says his party was caught by surprise by the leak, and says many Germans' fears were rooted in what he calls "disinformation" from early German press reports.

"They were full of false narratives, wrong numbers, false facts," he says. "A lot of these were being peddled not only by the opposition, but also by our own government coalition partner, the libertarian FDP party. Suddenly the news narrative was that everyone has to change their heating systems starting this winter."

The Green Party has not done enough to counter this narrative, though, and German homeowners are scared that as part of their country's commitments to reducing carbon emissions by more than half of 1990 levels by the end of the decade, they'll now have to make costly changes to their home heating systems.

"This law will instantly reduce the value of the building stock and Germany in a very dramatic way," says Kai Warnecke, president of Haus und Grund, an association that represents nearly a million private homeowners and landlords. "The estimation for a standard one-family house which needs to be redone and have a heat pump installed is around 150,000 euros [$163,725], and therefore the calculated outcome for the whole German building stock is, on a conservative level, 1 trillion euros [$1.091 trillion]."

That's equal to about a quarter of Germany's GDP last year.

Warnecke warns this bill, should it become law, would bankrupt middle class homeowners and send the country's economy into a freefall, despite promises by the Greens to dole out subsidies to middle class homeowners to help with heat pump installations.

But earlier this month, as Germany's parliament began debating the bill, it became clear the Green Party may be willing to compromise — only requiring new buildings to conform to the new rules and giving homeowners more time to comply.

That should be a relief to German homeowners. But Andree Boehling, an energy expert at Greenpeace, says the climate can't wait.

"Any energy expert will tell you that it's patently clear that this revised bill – in its current state – will result in Germany failing to hit its 2030 climate protection targets," says Boehling. "Now it's up to parliament to ensure the bill is tightened up with stricter measures."

Outside Berlin's parliament building, Tanja Baer, a 44-year-old chemistry teacher visiting from the city of Mainz, says she's watching all of this closely. "I'm all for climate protection, but the way and the speed at which the Green Party wants to do this is simply too much," says Baer.

Baer and her husband have four children and they're looking to buy a new house. She says they can only afford an older home with a gas or oil boiler, and there's no way they can afford replacing that with a new heat pump, even with subsidies the Green Party is promising.

"I used to vote for the Green Party, but no more," says Baer. "The party has simply disappointed me too many times."

NPR producer Esme Nicholson contributed to this report from Berlin.

Copyright 2023 NPR. To see more, visit https://www.npr.org.