Heat Pump Size Calculator
Find what size heat pump you need in tons for your square footage and climate, and whether a standard or cold-climate model is right for your winters.
Heat pumps are sized in tons, and the makers' rule depends on your climate more than anything else. This gives you the size to shop for, the square footage that size covers where you live, and whether a standard or a cold-climate model is the right kind for your winters.
Conditioned square feet
The space the heat pump heats and cools: finished living area, not the garage or an unfinished basement. A typical home is 1,500–2,500 sq ft.
Your climate
Hot is the South and Southwest, where cooling sets the size. Cold is the Northeast, upper Midwest and mountain states, where heating does. Moderate is in between: the Mid-Atlantic, lower Midwest and the West Coast.
How well the house holds heat
Tight is newer or sealed, with good insulation and double-pane windows; drafty is an older house with single-pane windows and little insulation. It moves the size within your climate's range.
What kind of heat pump
A heat pump makes less heat the colder it gets outside. Cold-climate models are built to keep going below zero; standard models lean on their built-in electric backup sooner.
Look for a
3.5-ton heat pump
The size an installer would quote for 2,000 sq ft in a moderate climate
The backup heater is normal, not a flaw
Every ducted heat pump comes with an electric heater built into the air handler, because a heat pump makes less heat the colder it gets outside and there are a few nights a year when it can't keep up alone. In a moderate climate with this unit that's a handful of the coldest nights; the rest of the time the heat pump carries the house at a third of the backup's running cost. Two things to ask the installer for: a load calculation (called a Manual J) to confirm the size before you sign, and a backup lockout set so the electric heater only runs when it's truly needed, not every time the thermostat is nudged up.
Size follows the makers' rule of 20–35 BTU per square foot by climate (one ton is 12,000 BTU an hour), rounded up to a stock size from 1.5 to 5 tons. The winter verdict comes from published cold-weather performance: standard units lose a third to half their heat by 17°F; cold-climate models keep at least 70 percent at 5°F. A Manual J load calculation replaces all of this. 2026 figures.
💡About this calculator▼
Heat pumps are sized in tons, and the makers' rule is simple: about 20 BTU per square foot in a moderate climate, more where summers are hot and more again where winters are cold, rounded up to a stock size. One ton is 12,000 BTU an hour, so a 2,000 square foot house in a moderate climate lands on a 3.5-ton unit.
This gives you the size and the kind. Enter the conditioned square feet, your climate and how well the house holds heat, and the calculator names the tonnage an installer would quote and the square footage that size covers for a house like yours. Then pick standard or cold-climate and it tells you whether that's the right kind for your winters.
The kind matters as much as the size. A heat pump makes less heat the colder it gets outside. Where winters are mild that only shows on a few nights, and the electric backup heater built into every ducted heat pump covers them. Where 17°F is a normal week, a standard unit leans on that backup for weeks, and a cold-climate model, certified to keep at least 70 percent of its heat at 5°F, is the right buy.
Start with the makers' rule. Carrier sizes heat pumps at about 20 BTU per square foot in a moderate climate, 25 to 30 in a hot one and 30 to 35 in a cold one, where the heating side drives the size; Trane's version is 600 square feet per ton for an existing house. Insulation sets where in the range you sit. One ton is 12,000 BTU an hour.
Round to a stock size. Residential units come in 1.5, 2, 2.5, 3, 3.5, 4 and 5 tons. The calculator takes the smallest at or above your figure; a 5-ton is accepted down to 90 percent of the figure, the floor the equipment-selection standard allows, and beyond that the answer is two systems. A stock size more than 125 percent of the figure is flagged as oversized, because an oversized heat pump short-cycles and leaves the air clammy.
Say what it covers. The coverage row is the stock size divided by your rate: the square footage a house like yours that unit carries, which is how the makers publish it.
Pick the kind for your winters. Standard heat pumps lose 30 to 50 percent of their heat by 17°F and more than half near zero, so in a cold climate the calculator says get a cold-climate model, which is certified to keep at least 70 percent of its heat at 5°F. In a moderate or hot climate a standard model is fine, and its built-in backup heater covers the few coldest nights.
Worked example. A 2,000 sq ft average house in a moderate climate: 20 × 2,000 = 40,000 BTU, so a 3.5-ton unit (42,000 BTU, 105 percent of the figure), which covers a house like it up to about 2,100 square feet. Standard is fine for those winters.
📐How it's calculated▼
Capacity figure (BTU/hr) = square feet × climate rate. Hot 25 (tight) to 30 (drafty); moderate 18 to 22; cold 30 to 35.
Tons = the smallest stock size (1.5, 2, 2.5, 3, 3.5, 4, 5) at or above the figure; a 5-ton is accepted down to 90 percent; beyond that, two systems. Oversized if the stock size is more than 125 percent of the figure.
Covers = the stock size's capacity ÷ your rate, rounded to 50 sq ft.
Default (2,000 sq ft, moderate, average): 40,000 → 3.5 tons (42,000, 105 percent); covers about 2,100 sq ft.
1,800 sq ft, moderate, average: 36,000 → 3 tons at 100 percent, the size both major makers list for it.
1,500 sq ft, cold, tight: 45,000 → 4 tons; cold-climate model recommended.
600 sq ft, moderate, tight: 11,000, and a 1.5-ton is 164 percent of it: oversized, look at a mini-split.
📎Sources:Carrier — Heat Pump Size Calculator (BTU per square foot by climate, tonnage table),Trane — What Size Heat Pump Do I Need? (square feet per ton, sizing chart),NEEP — Cold Climate Air Source Heat Pump Specification, Version 4.0 (capacity at 5°F ≥ 70% of rated),ASPE Pipeline — Low-Ambient Derating in Heat Pumps (capacity loss by outdoor temperature, 2026)
🔍Finding your inputs▼
Conditioned square feet: The space the system heats and cools: finished living area, not the garage, attic or an unfinished basement. A typical home is 1,500 to 2,500. If you're between sizes, the smaller figure is usually the safer one for a heat pump, because oversizing hurts dehumidification and cycling.
Your climate: Hot is the South and Southwest, where cooling sets the size and 17°F is a rare freeze. Cold is the Northeast, upper Midwest and mountain states, where heating sets it. Moderate is the Mid-Atlantic, lower Midwest and the West Coast.
How well the house holds heat: Tight is newer construction or a sealed older house with good insulation and double-pane windows; drafty is single-pane windows, little insulation and air you can feel. It moves the size within your climate's range, and it's the input with the most room for error, so if you're unsure pick average.
What kind of heat pump: Standard units are fine where winters are mild and lean on their built-in electric backup on the coldest nights. Cold-climate units are certified to keep at least 70 percent of their heat at 5°F and carry a house through a real winter mostly on their own; they cost more. The card changes the winter verdict, not the size.
⚠️Special situations▼
The contractor quoted a 4-ton for my 2,000 sq ft house and the calculator says 3.5. Who is right?
Ask for the Manual J. Both sizes sit inside the selection window (a 4-ton is 120 percent of the 40,000 BTU figure, under the 125 percent limit), so neither is wrong on its face, but a heat pump that's a half ton big short-cycles in summer and pulls less humidity out of the air. If the contractor sized up for winter heating, that's the wrong tool: the cold nights are what the backup heater and a cold-climate model are for, not extra tonnage that's oversized for eight months a year.
Why does every heat pump come with an electric backup heater? Doesn't that mean it can't do the job?
It means it can't do the job on the coldest few nights, which is true of every air-source heat pump, because there's less heat in the air to pull as it gets colder. The backup is an electric heater in the air handler that runs alongside the heat pump when the outdoor temperature drops below the point where it keeps up. In a moderate climate that's a handful of nights a year; the rest of the winter the heat pump carries the house at about a third of the backup's running cost. Have the installer set the backup lockout so it doesn't run every time the thermostat is nudged.
I live in Minnesota. Can a heat pump really heat my house?
A cold-climate model can. Standard units lose more than half their heat near zero, but cold-climate models are certified to keep at least 70 percent at 5°F and many hold more, so they carry a well-sized house through most of the winter on their own with the backup covering the deepest cold. Size it by the cold-climate rate, 30 to 35 BTU per square foot, choose a variable-speed model from the NEEP cold-climate list so it can turn down in summer, and have the backup heater sized from the load calculation.
My 600 sq ft addition comes out oversized even at 1.5 tons.
The smallest ducted stock size is 18,000 BTU, and a tight 600 sq ft space needs about 11,000, so a 1.5-ton runs at 164 percent of the load: short cycles, clammy air, early wear. The right equipment is one that turns itself down: a ductless mini-split sized to the load, usually a 9,000 or 12,000 BTU head, or a variable-speed unit that can run at a third of its rating. Our mini-split installation cost page prices that route.
❓Common questions▼
What size heat pump do I need for 1,500 square feet?
About 30,000 BTU, a 2.5-ton unit, in a moderate climate with average insulation; a drafty house in the same climate lands at 3 tons. In a hot climate the figure is 37,500 to 45,000 BTU, a 3.5- or 4-ton, and in a cold climate 45,000 to 52,500, a 4- or 4.5-ton, where the heating side drives it. The makers' rule is 20 to 35 BTU per square foot by climate, and one ton is 12,000 BTU.
How many square feet does a 3-ton heat pump cover?
About 1,500 to 2,000 square feet in a moderate climate, the range Carrier and Trane both publish, at roughly 20 BTU per square foot. In a hot climate the same 36,000 BTU covers about 1,200 to 1,450 square feet, and in a cold one 1,000 to 1,200, because the heating side needs more capacity per square foot there.
What is a cold-climate heat pump and do I need one?
A heat pump built to keep making heat well below freezing. The industry specification certifies models that keep at least 70 percent of their rated heat at 5°F, where a standard unit has lost more than half. If your winters regularly sit below about 20°F, get one: a standard unit there runs its electric backup for weeks at about three times the cost per hour of heat. In a moderate or hot climate a standard model is fine and the backup only runs a few nights a year.
Is a bigger heat pump better for cold weather?
Usually not. The selection standard caps capacity at about 125 percent of the summer load, and a unit sized for winter is oversized for eight months: it short-cycles, wears sooner and leaves the air clammy because it doesn't run long enough to dehumidify. The tools for winter are a cold-climate model, a variable-speed unit that can run low in summer and high in winter, and a properly sized backup heater for the coldest hours.
Why does my heat pump need backup heat?
Because it pulls heat out of outdoor air, and there's less to pull as the air gets colder. A standard unit loses 30 to 50 percent of its capacity by 17°F and more than half near 0°F, while the house needs the most heat at exactly those temperatures. The outdoor temperature where the heat pump's output equals what the house needs is called the balance point; below it, the electric heater in the air handler makes up the difference. Cold-climate models push that point far lower.
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