What Are Heat Pumps, and How Do They Work?

Heat pumps, which both warm and cool buildings and are powered by electricity, have been touted as the answer to curbing greenhouse gas emissions produced by homes, businesses and office buildings, which are responsible for about one-third of the emissions in New York State.

But how do they work? How much do they cost? Is New York ready for them? And can they really help solve the climate crisis? Here are some heat pump basics.

Why are heat pumps better for the environment?

Currently, we mostly burn fossil fuels to produce heat. This causes pollution. Heat pumps are all-electric.

Even though most electricity still comes from combustion, the United States is slowly transitioning to renewable power like hydro, wind and solar. As this shift occurs, heat pumps will help eliminate greenhouse gases.

A heat pump moves heat.

It consists of a boxy component outside and a sleek-looking blower inside. A thermostat controls the temperature. During warm weather, a pump works just like an air-conditioner by rerouting indoor heat outdoors.

When it’s cold outside, the process is reversed: Heat from the chilly outdoor air is extracted and delivered indoors with the help of refrigerants and a compressor.

Will heat pumps overburden the electricity grid?

New York City’s transition to renewable energy and electrification is happening gradually, involving many projects and moving parts. Con Edison is making investments in the grid to prepare it for an increase in demand, said Jen Hensley, a senior vice president at the company. But for the time being, the grid is ready for heat pumps, she added.

The devices are highly efficient, which should help limit the growing burden on the grid, said Rohit T. Aggarwala, the city’s climate chief.

Miguel Modestino, the director of the sustainable engineering initiative at the Tandon School of Engineering at New York University, explained the pumps’ efficiency: They move heat, they don’t create it. Using the same amount of electricity, a heat pump can provide three to four times more warmth than a plug-in space heater.

Is there more than one kind of heat pump?

Yes. Air-source heat pumps are the most common. Geothermal pumps, another kind, take in heat from below the ground, where the temperature is more stable, Dr. Modestino said.

Geothermal systems, which tend to be more expensive to install, can provide energy for large buildings and even entire communities. But in New York City, where the real estate underground is jammed with pipes, cables and subway tunnels, geothermal pumps, with a few notable exceptions, can be difficult to install. So air-source pumps work better in the city.

What kinds of buildings can use the pumps?

Small buildings (one- to four-family homes and some businesses) are ideal.

New constructions are using larger-scale heat pumps, which can be placed on roofs or across entire floors, said Greg Elcock, vice president for energy efficiency at Con Ed.

It’s the older, larger buildings that are the problem, he said. “We call them the hard-to-electrify stock.”

Installing heat pump pipes across more than 12 stories of a building is still a major challenge, said Pallavi Mantha, an associate at Arup, a global sustainable-development company.

The large buildings are the worst polluters. How can they reach New York’s climate goals?

City law states that properties larger than 25,000 square feet — of which there are about 50,000 — must curb their emissions by 40 percent by 2030.

A state program is helping several city properties, like the Empire State Building, develop heat recovery systems and partial electrification plans. But “there are still technical advances that are happening and we don’t have all the answers yet,” Ms. Mantha said.

Until then, buildings can take an incremental approach by replacing windows, improving insulation, and reducing consumption, Ms. Mantha said.

“If you do all this, it creates an enabling path for electrification,” she said. “It’s buying time until the technology and policy evolve.”

Are people really buying heat pumps?

They are starting to. In New York City, Con Ed customers have completed more than 30,000 installations since 2020. And across the state, nearly 23,000 heat pump projects were installed in 2022, a threefold increase from the year before.

In the United States, shipments of heat pumps outpaced those of gas furnaces by over 15,000 units in January, according to the Air-Conditioning, Heating and Refrigeration Institute, a trade association for manufacturers.

“I’m an evangelist,” said James Rosenthal, who owns an apartment in a 29-unit co-op in Lower Manhattan. Although his building runs on gas, which he still uses for cooking and heating water, he converted his home to rely on heat pumps in 2022. Since then, he has convinced six other neighbors to do the same. Their units were installed either at the base of the building or on its roof.

Aren’t they expensive?

Yes. Installing a heat pump in a single-family home can cost upward of $20,000.

There are financing options, however. Through 2032, a federal tax credit of up to $2,000 is available for installation, and New York State’s Clean Heat program offers rebates through utility companies that can amount to between $8,000 and $12,000 in savings, according to a Con Ed spokesman. There is also financial assistance available specifically for low- and middle-income households. And Mr. Rosenthal said his electricity bills were about 30 percent less in the summer, spring and fall.

Later this year, the Inflation Reduction Act is expected to release more funding for New Yorkers, state officials said.

Is it a pain to install one?

Like any home project, the experience can vary. “It’s major surgery,” said Mr. Rosenthal, who compared the weekslong construction to a renovation. “It was surgical,” said Robert Montalvo, a homeowner in the Bronx, whose pump system was installed in one day.

The level of disruption and duration of the project depends on the space and the piping work involved, said Victor Rodriguez, whose Brooklyn company, Ice Age Mechanical, installs heat pumps in small buildings and homes.

But the steps are always the same, he said, adding that sometimes the process can slow down if a building’s electrical system needs to be upgraded.

“This is the new way forward,” Mr. Rodriguez said. “We are kept pretty busy.”