Few climate technologies have ever had a moment quite like the one heat pumps are currently enjoying.
While the share of electric vehicles and induction stoves sales may be growing, they still represent a sliver of all cars and stoves sold respectively. US heat pump sales, though, surpassed those of gas furnaces last year as the tech of choice to keep homes comfortable.
The sudden rise of the heat pump may have you wondering: what actually are they, how do they work, and are there incentives that can help lower the price?
What does a heat pump do?
Calling it a “heat pump” is perhaps a bit misleading. That’s because heat pumps both heat and cool your home depending on the season. To do this, they use electricity rather than methane gas, cutting down harmful greenhouse gas emissions and public health and safety concerns.
“It sounds like magic,” said Vince Romanin, the founder of window heat pump startup Gradient. Spoiler: it’s just physics.
How do they work?
The short answer is they work by moving – pumping, if you will – heat from one place to another. It’s actually the same thing that air conditioners do: they pump heat out of your house and draw cool air in. If you’ve ever stood outside next to an air conditioner, you can feel that heat being pushed out. A heat pump can do that same task in summer, but in winter, it also has the ability to reverse the process and pull heat in from the outside into your home. Some heat pumps, called ground source heat pumps, use the ground outside a home as a place to pull or dump heat.
Are heat pumps better than gas furnaces?
In many cases, yes. They’re wildly more efficient. It’s a lot easier to move heat around rather than creating it from scratch by lighting gas on fire and then blowing the resulting heat around. Romanin noted that heat pumps are 300% more efficient than gas furnaces.
“It is ridiculous to burn a fossil fuel at thousands of degrees to heat up your apartment by 10 to 20 degrees. It’s a crime against the laws of thermodynamics,” he said.
That efficiency can translate to cost savings. An analysis by Carbon Switch found switching from a gas furnace to a heat pump would save the average US household $557 a year on its home energy bill.
Beyond efficiency, it’s also much safer to not pipe gas into your home on a regular basis due to a range of public health and safety impacts. Improperly installed or maintained ventilation systems can result in pollution being sucked up into your home. Then there’s the danger of a flammable material being transported to and ignited in your basement.
We haven’t even gotten to the climate benefits yet. A study released last year found that replacing gas furnaces with heat pumps in every US home could cut carbon emissions by up to 53%. Meanwhile, the Carbon Switch analysis found home emissions would drop by 142m metric tons.
Do heat pumps work in cold weather?
Yes. Mostly.
The conventional wisdom has been that air source heat pumps don’t work well in cold weather, because it’s hard to extract heat from extremely cold air. Some systems also use energy-intensive forms of heating to prevent their icing up, cutting into efficiency gains. Ground source heat pumps have an easier time since the ground temperature remains fairly constant.
But “it’s astonishing what manufacturers, what universities have been able to do”, said Subhrajit Chakraborty, an R&D engineer at the University of California, Davis’s Western Cooling Efficiency Center.
Air source heat pumps have gotten much more efficient at capturing heat even when it’s sub-zero outside. This year, Energy Star, a US government program promoting energy-efficient appliances, launched a cold-climate rating for heat pumps. A database kept by the non-profit Northeast Energy Efficiency Partnerships shows there are more than 1,400 models that fit the bill.
Real-world tests in cold climates from Maine to Minnesota show that heat pumps can operate in some of the harshest winter conditions out there.
OK, and how much do they cost?
They aren’t overly cheap. In the US, installing a heat pump is a four- or possibly five-figure investment depending on the size of the house, climate and other factors. Air source heat pumps are generally cheaper than ground source ones, though Chakraborty said the efficiency gains of a ground source heat pump may make it more cost-effective over a 15-year or longer timescale.
Are there incentives to help me afford one?
There are. In the US, the Inflation Reduction Act includes tax credits that cover 30% of the cost of a heat pump up to $2,000 (about £1,700). For households with under 80% of the median area income, the law is even more generous. It will cover 100% of the upfront costs of buying and installing a heat pump up to $8,000 (about £6,700). Many states also offer rebates. Stacked together, these benefits could help make heat pumps accessible to everyone rather than just the well-off, who have traditionally bought them.
In the UK, the government offers homeowners up to £6,000 ($7,150) to cover installing a heat pump. The urgency to install more heat pumps has increased in the wake of the Ukraine war, yet a third of the £6.6bn ($7.8bn) put forward by the government for efficiency upgrades remains unspent as of last month.
Some Australian states as well as the federal government offer incentives for heat pump hot water heaters, a related type of technology that warms up water instead of space.
What stands in the way of installing a heat pump in every home?
For one, not everyone lives in a freestanding home. Apartment dwellers have had few options. Gradient and a growing number of HVAC companies in the US are looking to change that, though, by offering window heat pumps.
The Gradient model is a sleek-looking unit that sits like a saddle over your window sill and requires no professional installation. It works in more temperate climates, though Romanin said a cold-climate model is on the way. But the company, along with Midea America, are set to do a pilot in New York public housing starting this year that will install window heat pumps that can operate in colder temperatures as part of a $70m HVAC upgrade program.
Installing a heat pump and electrifying other appliances also might require homeowners to update their electrical panels, which can add another $1,300 to $3,000 to any project. (In the US, the IRA does include a $600 tax credit for those upgrades when done in conjunction with other electrification upgrades.)
What comes next for the humble heat pump?
Chakraborty’s group is working on a multifunction heat pump that can be used for space and hot water heating.
Romanin said new forms of heat-pump refrigerant are also making their way to the market. HFCs, currently some of the most common refrigerants, are also extremely potent greenhouse gases. They became widespread because they replaced CFCs, refrigerants that damaged the ozone layer. HFCs are now on their way out, but Romanin said “if we don’t focus on what we’re replacing them with, we could repeat this same mistake”.
Gradient uses a relatively low-impact HFC called R32. But he said “this is a stepping stone refrigerant for us”, and that the company is seeking even better options.
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