Air Source Heat Pumps: How They Work, Cost and Fit

An air source heat pump moves heat between your home and the outdoor air to both heat and cool, using electricity to run a compressor rather than burning fuel. Most US homes install a ducted central system or a mini split, and installed cost commonly runs from about $6,000 to $18,000. A separate, less common type is the air to water heat pump, which heats water for radiators or radiant floors instead of blowing warm air. This guide covers how the technology works, what it costs, and whether it fits your home.

What an air source heat pump actually does

A furnace makes heat by burning gas or oil. A heat pump does not make heat; it moves it. Even cold outdoor air holds usable thermal energy, and a heat pump uses a refrigerant loop to absorb that energy outside and release it inside. In summer the same loop runs in reverse, pulling heat out of your house and dumping it outdoors, which is why one machine replaces both a furnace and an air conditioner.

Because it moves heat instead of generating it, the machine delivers more heating energy than the electricity it consumes. That ratio is the COP, and for a modern unit it typically sits between 2 and 4. A COP of 3 means you get roughly three units of heat for every one unit of electricity, which is the core reason heat pumps can heat cheaper than resistance electric or, in many regions, propane and oil. For a plain-English primer, see our page on what a heat pump is and the deeper walk-through of how heat pumps work.

Air to air vs air to water

The phrase “air source heat pump” covers two designs that share the same outdoor unit concept but deliver heat differently.

Air to air (the common US system)

This is what most American installers mean by a heat pump. An outdoor condenser connects to an indoor air handler or to wall-mounted heads, and it moves heat directly into the air you breathe. It works with existing ductwork or as a ductless mini split.

Air to water

An air to water heat pump sends heat into a water loop that feeds radiators, a radiant floor, or a buffer tank, and it can also make domestic hot water. It is common in Europe and in homes with hydronic heating, but far less common in US new construction. If your house already runs on radiators or radiant floors, air to water lets you keep those emitters while dropping the fossil boiler. Expect a smaller installer pool and, often, a higher project cost than a comparable air to air system because of the water loop and controls.

What an air source heat pump costs

Installed cost depends on system type, capacity in tons, efficiency rating, and the state of your ductwork. These are typical 2026 US ranges before any incentives.

* Ranges reflect equipment, labor, and typical ductwork adjustments. Electrical panel upgrades, long line sets, and difficult access can push costs higher.

The single biggest swing factor is ductwork. Reusing sound ducts keeps a ducted job toward the lower end; adding or heavily modifying ducts pushes it up, and at that point a ductless system sometimes wins on price. For a full breakdown by size and type, see our heat pump cost guide.

Incentives that lower the price

Federal and state programs can meaningfully cut what you actually pay, but they come with conditions.

• Federal 25C tax credit: 30% of the project cost, up to $2,000 per year for a qualifying heat pump that meets the required efficiency tier. It is nonrefundable, claimed on IRS Form 5695, so it offsets taxes you owe rather than arriving as a check.
• IRA rebates (HEEHRA/HEAR): income-qualified households may receive up to $8,000 toward a heat pump where available. These are state-administered and still rolling out, so check your state program before you count on them.
• Utility rebates: many local utilities add their own rebates for high-efficiency equipment. Ask your installer to list current offers in writing.

To qualify for the federal credit, the equipment has to hit the right efficiency tier, so the exact model on the quote matters. Our tax credit and rebates page walks through eligibility and stacking.

The sticker price and the price you actually pay can differ by several thousand dollars once credits and rebates land.

Efficiency ratings and what they mean

Since 2023, US ratings use an updated test standard. You will see three numbers on the equipment sheet.

SEER2 and HSPF2 are seasonal averages, so they predict real-world running cost better than a single peak number. A higher rating costs more upfront and saves more over the years; how fast it pays back depends on your climate and electricity price. For the full explanation, see SEER2, HSPF2 and COP made simple.

Cold weather, defrost, and backup heat

A common worry is that air source units quit in winter. Modern cold-climate models hold usable capacity down to roughly 5F and below, and many keep running well past that. Capacity does fall as it gets colder, and the machine runs a periodic defrost cycle to clear frost from the outdoor coil, which is normal and brief.

For the coldest hours, systems include auxiliary heat. That is usually electric resistance strips in the air handler, or in a dual-fuel setup, a gas furnace that takes over when it is cheaper or colder. Sizing the backup correctly matters as much as sizing the heat pump. To see how these units perform through a real winter, read do heat pumps work in cold climates.

Will it fit your home?

Fit comes down to sizing and your existing heating setup. Capacity is measured in tons, where 1 ton equals 12,000 BTU per hour. A rough rule of 20 to 30 BTU per square foot gives a ballpark, but it varies widely by climate, insulation, windows, and air sealing.

The real answer is a Manual J load calculation, which a good installer performs before quoting. Oversizing is a real problem: an oversized unit short-cycles, meaning it turns on and off too often, which hurts comfort, humidity control, and equipment life. Undersizing leaves you cold on peak days. Get the load calc right and the rest follows. Our sizing guide explains tonnage and BTU math in detail.

• Have good ducts? A ducted central air to air unit is usually the straightforward path.
• No ducts, or uneven rooms? A ductless mini split avoids duct work and gives per-room control.
• Radiators or radiant floor? An air to water heat pump keeps those emitters.
• Very cold region? Specify a cold-climate model and plan the backup deliberately.

Getting a quote without getting oversold

Before you sign, make sure the quote names the exact model, states SEER2 and HSPF2, shows the Manual J result, and lists the backup heat plan and any incentives in writing. Vague quotes are where oversizing and padding hide. Compare at least two or three bids on the same scope, and read our guides on installation steps and reading quotes and avoiding being oversold before you commit.

An air source heat pump is the default choice for most US homes because it heats and cools with one electric machine, qualifies for real incentives, and now handles cold weather far better than its reputation suggests. The money question is not whether the technology works, but whether the specific system on your quote is sized right and priced fairly for your house.

Frequently asked questions