Heat pumps are the future of home climate control. They’re all electric, energy-efficient and can heat and cool homes to replace your home’s furnace and air conditioner in one go. There’s just one (fatal) flaw. In the deep cold of winter, they don’t work as well as a gas furnace. But newer models, like one unveiled by Bosch at CES 2024, are part of an effort to solve that problem and catapult heat pumps forward to become the future of both heating and air conditioning.
Heat pumps are seen as a key tool in America’s electrification and decarbonization. They can replace furnaces, which largely run on fossil fuels like natural gas, with an electric appliance. If that electricity is coming from a clean, renewable source like solar or wind, it cuts fossil fuels largely out of the energy equation.
Bosch’s new heat pump, the IDS Ultra, is the company’s first air-to-air heat pump designed specifically for colder climates. The model, which Bosch says can maintain a home’s temperature down to 5 degrees Fahrenheit and keep working down to minus-13 degrees, is one of several that has passed the first stage of the Department of Energy’s Residential Cold Climate Heat Pump Challenge. Others include products from Daikin, Midea, Johnson Controls, Lennox International, Carrier, Trane and Rheem.
“From a cold climate perspective, it’s really about the technology advancement,” said Ashley Armstrong, senior advisor in DOE’s Office of Energy Efficiency and Renewable Energy and program manager to the Office of State and Community Energy Programs.
Here’s why your next heating system might be all-electric, even if you get snow and frost.
Why cold-climate heat pumps matter
There are generally two types of heat pumps: air-source and geothermal heat pumps, but they both use similar principles to operate. To heat, they capture thermal energy from a source outside of your home (the air or the ground) and transfer it to your home using a pumped refrigerant. To cool your home, they do the same thing, just in reverse.
“In very simple terms, a heat pump is transferring heat from one side to the other,” David Lopes, director of marketing and business strategy at the Home Comfort Group for North America for Bosch, told CNET. “In the summertime it’s transferring heat from the inside to the outside. In the wintertime it’s the opposite.”
Air source heat pumps even work when it’s cold — there’s still thermal energy outside, just less of it, despite how it may feel. But they don’t work as well.
That’s why it’s important, both for the homeowners in cold climates and for the US energy transition generally, for heat pump technology to get better at operating below freezing.
A wide range of changes are needed to improve energy efficiency and reduce fossil fuel emissions all across the country, Armstrong said. “These cold-climate heat pumps, especially those that are next generation that can provide more heat in heat pump mode when temperatures get even colder, are just part of the suite of solutions that are needed to reduce energy consumption and also reduce onsite carbon emissions.”
Making a heat pump work in the cold
The problem with heat pumps in cold weather is the same as what anyone who’s been through a northern winter will tell you about roads: Ice makes everything stop.
The heat pump is cycling refrigerant through coils outside of your home, trying to pick up what thermal energy is available in the air. When it gets too cold, water in the air starts to condense on the coils and then freeze around them, blocking the refrigerant from being able to absorb that energy.
Heat pumps are equipped with defrosting technology to keep this from happening, but that usually means the pump’s energy is being spent trying to warm those coils up rather than warming up your house. At a certain point, if it’s too cold, it becomes a losing battle.
“In very cold weather situations it just ends up doing that the whole time and it never heats up the inside,” Lopes said.