ArticlesHeating a building is one of the largest uses of energy worldwide, and it is also one of the more stubborn sources of emissions. Heat pumps are often described as a way to reduce both energy use and carbon dioxide from heating. But how can a machine that runs on electricity deliver more heat than the electricity it consumes, and does it really work when the weather is freezing? This article explains the basic idea, summarizes what the International Energy Agency (IEA) and the U.S. ENERGY STAR program say, and lists practical points to check before considering one. It is general information, not advice for a particular home.
The core idea: moving heat instead of making it
A gas boiler or electric resistance heater creates heat by burning fuel or by passing current through an element. A heat pump moves heat that already exists. In winter it collects heat from outside air, the ground, or water, even when it feels cold, and delivers it indoors. Many models can also run in reverse in summer, taking heat out of the building the way an air conditioner does.
The moving is done with a refrigerant, a fluid that changes between liquid and gas. A compressor squeezes the gas, which raises its temperature, and the hot gas gives up heat to the indoor air or water as it condenses back into a liquid. An expansion valve then lowers the pressure, the fluid evaporates outdoors, absorbing heat from the surroundings, and the cycle repeats. This is the same cycle found in a refrigerator, applied in the opposite direction for heating. Describing the refrigerant cycle is standard physics background rather than a claim taken from the two sources cited below.
Because electricity is used to run the compressor and fans rather than to create the heat directly, the delivered heat can exceed the electrical input. The IEA reports that heat pumps currently available on the market are three to five times more energy efficient than natural gas boilers [1]. The comparison is between energy efficiency in typical operation, so real results depend on climate, installation, and how the system is used.
Why heating matters for energy and climate
The IEA's scale of the issue is striking. It says that over one sixth of global natural gas demand is used for heating buildings, and in the European Union that share is one third. Heating in buildings is responsible for 4 gigatonnes of carbon dioxide emissions each year, which is 10 percent of global emissions [1]. These figures come from a 2022 report, so they describe the situation at that time rather than today.
The agency concludes that heat pumps powered by low-emissions electricity are the central technology for a secure and sustainable heating transition. It adds that installing heat pumps in place of fossil-fuel boilers significantly reduces greenhouse gas emissions in all major heating markets, even with the current electricity mix, and that the advantage grows as electricity grids decarbonize [1]. In other words, a heat pump does not need a perfectly clean grid to come out ahead, though a cleaner grid improves the result.
Are heat pumps ready for cold weather?
A common worry is that heat pumps only suit mild climates. The IEA offers evidence against the blanket version of that claim: it says that in Norway, 60 percent of buildings were equipped with heat pumps, with Sweden and Finland above 40 percent, which undercuts the argument that heat pumps are unsuitable for cold climates [1].
ENERGY STAR, the U.S. government-backed efficiency program, explains the technology behind this. Many new certified air source heat pumps provide space heating even in the coldest climates, because they use advanced compressors and refrigerants that improve low-temperature performance. ENERGY STAR's cold climate certification requires third-party verified performance testing down to 5 degrees Fahrenheit. The program adds that a cold climate unit will keep working below 5 degrees Fahrenheit, but pairing it with a back-up energy source heats a home most efficiently when temperatures fall even lower [2]. Note the nuance: modern units can handle cold, but the program itself recommends talking with a contractor about the right unit and whether to include a back-up system.
Sizing and installation matter
A heat pump that is too large or too small for the home will struggle. ENERGY STAR says that proper sizing is essential for the best performance and comfort, and that a contractor should verify the right size with a calculation called Manual J, which estimates how much heating and cooling a home requires [2]. This ties to a point the IEA makes about buildings themselves. Households that add a heat pump without improving efficiency in parallel can nearly triple their peak winter electricity demand. Improving a home's efficiency rating by two grades, for example from D to B in European countries, can halve heating energy demand and reduce the heat pump size needed [1]. Practical translation: insulation and air sealing do not compete with a heat pump, they make a smaller and cheaper system possible.
Dual fuel systems
ENERGY STAR describes a dual fuel option for homes that already have a relatively new furnace paired with an older central air conditioner. Adding a certified heat pump creates a system that can heat with either the heat pump or the traditional furnace, allowing each to be used according to cost and environmental benefit [2]. For some households this can be a stepping stone, keeping the existing furnace as a backup while shifting most heating to electricity.
Costs, savings, and incentives
The IEA says that, over their lifetime, heat pumps can save consumers money and protect them from fuel price shocks. It reports that the average household or business using a heat pump spends less on energy than one using a gas boiler, and that these savings offset the higher upfront cost in many markets, in some even without subsidies. Its estimates of household savings, made in the context of the 2022 energy price spike, ranged from 300 US dollars per year in the United States to 900 US dollars in Europe [1]. Prices change, so check current local energy rates before assuming those figures apply to you.
ENERGY STAR notes that although these products can cost more upfront, the difference is repaid over time through lower energy bills. It also says certified air source heat pumps are eligible for a federal tax credit of up to 2,000 US dollars for products purchased and installed between January 1, 2023 and December 31, 2032, and that many utilities offer incentives as well [2]. Incentive rules can change over time and vary by location, so confirm the current terms with ENERGY STAR or your utility before relying on them.
Grid impacts and bigger picture
Widespread heat pump use means more electricity demand. The IEA reports that in a scenario where governments meet their announced climate and energy commitments, the share of electricity in building and industry heating doubles between 2021 and 2030 to 16 percent. Over the same period global electricity demand rises by a quarter, and heat pumps contribute less than one tenth of that rise. The agency says that efficiency improvements, demand response, and careful grid planning can greatly reduce the strain [1]. Heat pumps are also not limited to homes. The IEA notes that large heat pumps can provide heat up to 140 to 160 degrees Celsius for industry, with the paper, food, and chemicals sectors having the largest near-term opportunities [1].
Questions to ask before buying
What size does a Manual J calculation recommend for this home? [2] Is a cold climate certified model appropriate where I live, and do I need a back-up heat source? [2] Can I improve insulation or air sealing first, or at the same time? [1] What incentives and utility rebates apply now? [2] How does my local electricity price compare with my current fuel price? [1]
Takeaway
Heat pumps work by moving heat, which is why they can deliver several units of heat for each unit of electricity. The IEA's analysis supports their role in cutting heating emissions and energy bills, and ENERGY STAR's guidance shows that cold weather is a design question rather than an automatic barrier. The outcome in any single building depends on sizing, insulation, local prices, and the electricity mix, so treat the headline numbers as a starting point and get a qualified contractor's assessment.
Sources
[1] International Energy Agency, The Future of Heat Pumps: Executive Summary - https://www.iea.org/reports/the-future-of-heat-pumps/executive-summary
[2] ENERGY STAR, Air Source Heat Pumps - https://www.energystar.gov/products/air_source_heat_pumps