Heat Pump vs Gas Furnace: Emissions and Running Costs
In most regions, a heat pump produces fewer emissions than a gas furnace, and it can cost less to run—but neither result is guaranteed. Emissions depend on the electricity supply and equipment efficiency; running costs depend on local electricity and gas prices, climate, and how well the home is insulated.
How the two systems work
A gas furnace burns natural gas (or, in some homes, propane) to heat air that is sent through ducts. Its seasonal efficiency is commonly expressed as AFUE: an 80% AFUE furnace delivers about 80 units of heat to the home for every 100 units of fuel energy consumed over a season, with the remainder lost mainly through exhaust.
A heat pump uses electricity to move heat rather than generate it by combustion. In heating mode, it draws heat from outdoor air or the ground and transfers it indoors. Its efficiency is usually expressed as a coefficient of performance (COP), the heat delivered divided by electricity used. A COP of 3 means three units of heat for each unit of electricity. COP changes with outdoor temperature, equipment, and operating conditions.
Air-source heat pumps are the most common type. Cold-climate models can operate at lower outdoor temperatures than older designs, though their capacity and efficiency still fall as it gets colder. Some homes use backup electric resistance heat or a furnace when the heat pump cannot meet demand economically or comfortably. Ground-source systems draw on more stable ground temperatures but usually involve higher installation costs and site work.
Which option usually lowers emissions?
Heat pumps often have the emissions advantage because they avoid on-site fuel combustion and can deliver several units of heat per unit of electricity. But electricity generation can emit greenhouse gases, so the comparison depends on the grid mix and on the furnace’s actual seasonal efficiency. A gas furnace also has upstream emissions from producing and transporting fuel, in addition to carbon dioxide released when gas is burned.
As electricity gets cleaner, a heat pump’s emissions generally fall without replacing the equipment. The result can vary by location and time: a coal-heavy grid may make the advantage smaller, while a low-carbon grid makes it larger. The right comparison uses local, current emissions data and realistic seasonal performance—not just a product’s best-case rating.
There is no single emissions figure that applies to every house. Home size, insulation, thermostat settings, equipment sizing, defrost cycles, and backup-heat use all affect energy consumption. A poorly installed heat pump that relies heavily on resistance heat may not deliver the expected benefit.
Which costs less to run?
Compare the cost of delivered heat, rather than comparing a dollar per kilowatt-hour directly with a dollar per therm. One useful approximation is:
- Heat pump cost per unit of heat = electricity price per kWh ÷ seasonal COP.
- Gas furnace cost per unit of heat = gas price per unit of fuel ÷ fuel energy per unit × 1 ÷ furnace efficiency.
For a more familiar comparison, one therm of natural gas contains about 29.3 kWh of energy. If a furnace is 90% efficient, it delivers roughly 26.4 kWh of heat per therm before accounting for distribution losses. A heat pump with a seasonal COP of 3 would need about 8.8 kWh of electricity to deliver the same heat. Multiply each energy requirement by the local fuel price to compare operating costs. Use the same price units and include fixed charges only if they change because of the heating choice.
For example, if electricity costs 18 cents per kWh and gas costs $1.50 per therm, the simplified heat-pump cost for that amount of heat is about $1.58 (8.8 × $0.18), while gas is $1.50. Under those assumptions, gas is slightly cheaper to operate. If the heat pump’s seasonal COP is higher, or electricity is cheaper relative to gas, the result can reverse. This example excludes maintenance, fixed fees, and differences in distribution efficiency; it is not a prediction for a particular home.
Climate, comfort, and installation trade-offs
Cold weather does not automatically make a heat pump unsuitable. The practical question is whether the chosen model can supply enough heat at the home’s design temperature and what it costs to do so. In very cold conditions, a heat pump may need backup heat; electric resistance backup can raise bills sharply, while a dual-fuel system can switch to a furnace if that is cheaper or necessary.
Heat pumps can also provide cooling, potentially replacing a separate air conditioner. They often deliver air at a lower temperature than a furnace, which may feel different even when the room is comfortable. Proper sizing, duct condition, airflow, controls, and commissioning matter for either system. Oversizing or poor ductwork can undermine comfort and efficiency.
Installation cost is separate from running cost. Replacing a furnace with a heat pump may require electrical upgrades, duct changes, or new outdoor equipment. Conversely, an existing furnace and gas connection can make a furnace replacement less disruptive. Compare total ownership costs over the expected service period, including installation, maintenance, and any cooling equipment avoided—not just one winter’s bill.
How to make a fair comparison
Gather the information for your home and ask contractors to show their assumptions. Useful details include:
- Local electricity and gas rates, including seasonal pricing and relevant fixed charges.
- The furnace’s AFUE and the heat pump’s performance at temperatures typical of your winter, not only its headline rating.
- Estimated annual heating use, based on bills or a proper load calculation, plus expected backup-heating use.
- Whether existing ducts can deliver the required airflow and whether the electrical service can support the proposed equipment.
- Installed costs, maintenance needs, cooling benefits, and any applicable local incentives, checked with current official sources.
Do not compare a heat pump’s rated COP at mild conditions with a furnace’s seasonal AFUE as if the figures described identical conditions. Ask for a seasonal estimate and a cold-weather capacity check. Also distinguish household emissions from upstream emissions: a gas bill may omit methane leakage in the fuel supply chain, while electricity emissions depend on generation and grid accounting.
Common misconceptions and practical cautions
“A heat pump always costs less” is too broad: unfavorable electricity-to-gas prices or very cold operating conditions can make it more expensive. “A furnace is always cleaner in a cold climate” is also too broad: grid emissions, seasonal performance, and backup use determine the comparison. Neither system is automatically cheaper or cleaner based on its name alone.
Never block outdoor heat-pump airflow with snow, leaves, or stored items; follow the equipment manual for clearing and maintenance. Keep furnace vents and combustion-air openings unobstructed, and have fuel-burning equipment inspected and maintained according to the manufacturer’s instructions and local requirements. A carbon monoxide alarm is an important safety measure in homes with combustion appliances, but it does not replace maintenance. If an alarm sounds or occupants feel unwell, leave the area and contact emergency services or the appropriate local authority.
Frequently Asked Questions
Is a heat pump cheaper to run than a gas furnace?
Sometimes. It depends on local energy prices, the heat pump’s seasonal COP, furnace efficiency, climate, and backup-heat use. Compare the cost of delivering the same amount of heat using your own rates.
Does a heat pump produce fewer emissions than natural gas?
Often, but not everywhere or in every operating condition. The answer depends on electricity-generation emissions and seasonal equipment performance, as well as emissions from producing and transporting gas.
Can a heat pump work in a very cold climate?
Many models can heat in cold weather, but capacity and efficiency decline as temperatures fall. Check performance at local winter temperatures and confirm whether backup heat is needed.
What is a dual-fuel heating system?
It pairs an electric heat pump with a gas furnace. Controls can use the heat pump in suitable conditions and switch to the furnace when the heat pump cannot meet the load or another operating point is preferred.
Should I replace a working gas furnace with a heat pump?
There is no universal answer. Compare installation cost, expected energy bills, cooling needs, emissions, equipment condition, and the home’s electrical and duct capacity before deciding.
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Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.