Heat Pump Size Calculator

What Size Heat Pump Do I Need?

The right heat pump size depends on more than just your home's square footage. Climate zone, insulation quality, window exposure, ceiling height, and ductwork condition all play a significant role in determining how much heating and cooling capacity your home actually needs.

Our heat pump size calculator above gives you an estimate in both BTU/hr and tons, using climate-adjusted base loads and real-world heat-loss factors. Two homes with the same square footage in different climates - or with different insulation levels - can need very different equipment sizes.

People put the question many ways: what size heat pump for my house, how big of a heat pump do I need, how many ton heat pump do I need, how do I know what size heat pump I need. Every version ends at one number, the load in BTU. That makes the tool above a heat pump load calculator and a heat pump size estimator in one, and it is built for the ducted air source heat pump most US homes use, so it also answers what size air source heat pump do I need.

An oversized heat pump causes short cycling, poor humidity control, and wasted energy. If the humidity problem is already there and replacing the equipment is not on the table this year, our dehumidifier sizing calculator works out what capacity it would take to fix it separately. An undersized one runs constantly, struggles in extreme weather, and drives up utility bills. Getting the size right is the single most important decision when buying a heat pump.

How to Calculate Heat Pump Size

If you want to know how to size a heat pump by hand, this is the whole method, and it works as a short heat pump sizing guide. The calculator uses a straightforward but effective method that goes beyond basic rules of thumb:

1. Start with a base BTU per square foot based on your climate zone - from 18 BTU/sq ft in a temperate climate to 28 in a hot and humid one and 30 in a cold one.
2. Multiply by adjustment factors for insulation and air sealing, ceiling height, windows and sun exposure, ductwork condition, home type, humidity demand, and extreme cold conditions.
3. Calculate the target BTU load, then create a ±10% range to reflect real-world uncertainty.
4. Convert to tonnage at 12,000 BTU per ton, and match to the nearest standard equipment size.

This approach is better than a generic square-foot rule but is not a replacement for a professional Manual J load calculation. It's designed to give you a directionally correct, practically useful estimate.

Heat Pump Sizing: Matching the Heating Load and the Cooling Load

Here is the thing that makes heat pump sizing different from sizing an air conditioner, and it is the part most guides skip. A heat pump is one machine doing two jobs, and the two jobs almost never ask for the same size. Outside the mild middle of the country your house does not lose heat in January at the same rate it gains heat in July, so there are two right answers and you have to pick one.

In the North the heating load is the bigger number. In the hot South it is the cooling load. The further you are from the middle, the wider the gap, which is why the same square footage gets different advice in Minnesota and in Georgia.

Size to the cooling load and you get a unit that dehumidifies properly all summer, but on the coldest nights it cannot keep up on its own and the backup heat fills the gap. Electric backup is resistance heat, so those hours cost roughly three times what the heat pump costs to run. A handful of hours a year is nothing. A hundred hours a year shows up on the bill.

Size to the heating load and you have a unit that carries the winter alone, but is now oversized for July, which brings the short cycling and weak moisture removal described in the oversized section below.

The number that decides which of those matters to you is the balance point: the outdoor temperature at which the heat pump's output drops to exactly match the heat your house is losing. Above it the heat pump holds the house by itself; below it the backup starts running. You find yours by taking the capacity table for the specific unit you are being quoted, which lists output at 47°F and 17°F, and seeing where that line crosses your heating load. A contractor who cannot produce that table for a unit they are quoting has not done the sizing.

One thing has genuinely changed the old advice: variable-speed equipment. A single-stage unit is either off or flat out, so oversizing it for winter guarantees a bad summer. An inverter-driven unit modulates down to a fraction of its rated output, so it can carry a larger heating capacity without short cycling in cooling. That is why cold-climate sizing guidance now depends on which kind of equipment you are buying, and why advice written for single-stage systems reads as too cautious today.

Tip: size to the cooling load, then check the balance point before you accept it. If the backup would run only on the coldest handful of nights, take the cooling-load size and keep the good summer. If your climate pushes the balance point up into temperatures you see for weeks at a time, that is the case for going up a size, and it is a much stronger case if the equipment is variable-speed.

Heat Pump Size by Square Footage

Square footage is the starting point for heat pump sizing, but it's not the whole story. The table below shows approximate sizing ranges based on a mixed climate with average home conditions. Your actual result may vary significantly based on insulation, windows, and climate.

Tables of heat pump size square footage like this one hide the number underneath, which is heat pump BTU per square foot. The calculator starts from 24 BTU per sq ft on its Mixed/Humid setting, 28 on Hot/Humid, 30 on Cold and 18 on Temperate/Mild, then adjusts for your insulation, windows and ducts. That is why a heat pump size calculator by square footage alone can be a ton or more off: the same 2,000 sq ft house is 3 tons in a temperate climate and 5 or more in a cold one.

What Size Heat Pump for 1000 Sq Ft

A 1,000 sq ft home typically needs 1.5 to 2.5 tons. In a mild climate with good insulation, 1.5 tons is often sufficient. In a cold climate with poor insulation or high ceilings, the requirement can push toward 2.5 tons or more. Climate and insulation are the biggest variables at this home size.

On the calculator's default inputs, heat pump size for 1000 sq ft is 2 tons on the Mixed/Humid setting, from a load of about 24,700 BTU. What size heat pump for 1000 sq ft house in a temperate climate? 1.5 tons, and 2.5 on Hot/Humid or Cold.

What Size Heat Pump for 1200 Sq Ft

A 1,200 sq ft home generally needs 2 to 3 tons. Average conditions in a mixed climate typically land around 2 to 2.5 tons. Leaky ductwork, lots of windows, or a very cold climate can push the requirement closer to 3 tons.

The load here is about 29,700 BTU for a mixed-humid zone, so heat pump size for 1200 sq ft comes out at 2.5 tons on the default inputs. It is 2 tons in a temperate climate and 3 tons in a hot and humid or a cold one.

What Size Heat Pump for 1500 Sq Ft

A 1,500 sq ft home usually requires 2.5 to 3.5 tons. This is the most common home size for heat pump installations, and a 3-ton unit is the typical starting recommendation for a mixed climate with average conditions. Better insulation can reduce the need, while cold climates and large windows increase it.

How many ton heat pump for 1500 square feet depends on the zone. The calculator gives 3 tons for Mixed/Humid, from about 37,100 BTU, 3.5 tons for Hot/Humid and 4 tons for Cold, and on Temperate/Mild it is 2 to 2.5.

What Size Heat Pump for 1800 Sq Ft

A 1,800 sq ft home typically needs 3 to 4 tons. Two-story layouts may need slightly more capacity than single-story homes because of increased exterior wall area. Insulation quality and climate zone remain the dominant factors.

At this size the load is about 44,500 BTU at mixed-humid rates, which is why the calculator shows 3.5 to 4 tons. What size heat pump for 1800 sq ft house in a hot and humid or a cold climate is 4 to 5 tons, and 2.5 to 3 where it is temperate.

What Size Heat Pump for 2000 Sq Ft

A 2,000 sq ft home generally requires 3 to 4.5 tons. In warm climates with good insulation, 3 tons may be adequate. In cold climates or homes with many large windows and high ceilings, 4 to 4.5 tons is more realistic. This size often benefits most from a proper Manual J calculation.

Run the default inputs and what size heat pump for 2000 sq ft house comes to 4 tons for a mixed-humid zone, about 49,400 BTU. In a cold climate, heat pump size for 2000 sq ft passes 5 tons, which means two systems or a cold-climate model, and in a temperate climate it is 3. So the tonnage has no single answer until the climate is fixed.

What Size Heat Pump for 2500 Sq Ft

A 2,500 sq ft home typically needs 4 to 5 tons or more. At this size, the impact of insulation, ductwork, and layout is magnified. A professional load calculation is highly recommended to avoid oversizing, which is a common problem with larger homes.

The calculator puts 2,500 sq ft at about 61,800 BTU on the Mixed/Humid setting, just over 5 tons, so it shows 5+ in every climate except the temperate one, where 4 tons covers it.

What Size Heat Pump for 3000 Sq Ft

A 3,000 sq ft home often requires 5 tons or more. Some homes this size may need multiple systems or a zoned approach. A proper Manual J calculation is essential at this size to determine the right solution - a single oversized unit is rarely the best approach.

For most climates, what size heat pump for 3000 sq ft house is a two-system question. The load is about 74,200 BTU at mixed-humid rates, a little over 6 tons, and only a temperate climate brings it back to a single 4 to 5 ton unit.

In-Between Sizes: 900 and 2,200 Sq Ft Homes

Homes rarely land on a round number. On the default inputs, heat pump size for 900 square feet is 2 tons on Mixed/Humid, from about 22,200 BTU. It is 1.5 tons on Temperate/Mild and 2 to 2.5 tons on Hot/Humid or Cold.

Go up to 2,200 and the answer moves fast with climate. Heat pump size for 2200 sq ft is 4 to 5 tons on Mixed/Humid, from about 54,400 BTU, 3.5 tons on Temperate/Mild, and past 5 tons on Hot/Humid or Cold. A manufactured home is a separate case because it loses heat through the floor, so for heat pump size for mobile home use the mobile home AC size calculator instead.

Heat Pump BTU and Tonnage Chart

Heat pump capacity is measured in BTUs per hour (BTU/hr). One ton of cooling or heating capacity equals 12,000 BTU/hr. The term “ton” comes from the amount of energy needed to melt one ton of ice in 24 hours. This is the heat pump sizing chart, also called a heat pump size chart. Here is a quick reference chart:

It's important to understand that nominal tonnage is not the full story in cold climates. A heat pump's actual heating output drops as outdoor temperatures fall. That's why cold-climate models are tested for low-temperature performance - the nameplate tonnage alone doesn't tell you how much heat the unit can deliver when you need it most.

Heat Pump Square Footage by Tonnage: How Much Each Size Covers

The sections above work forwards, from your home size to a tonnage. Plenty of people arrive from the other direction: a contractor has quoted a specific unit, and the question is whether that size actually fits the house. These are the same numbers read in reverse. Treat every range as a starting point, because climate zone and insulation move the answer more than floor area alone does.

1 Ton Heat Pump Square Footage and the Small BTU Sizes

Below 1.5 tons the equipment is nearly always ductless, and it is sold by BTU instead of tons. With the calculator left on its defaults, each ton covers about 485 sq ft on Mixed/Humid. So 1 ton heat pump square footage, the same thing as 12000 BTU heat pump square footage, is about 485 sq ft.

By the same arithmetic, 9000 BTU heat pump square footage is about 365 sq ft, 18000 BTU heat pump square footage about 730 and 24000 BTU heat pump square footage about 970. Those figures stretch by a third on Temperate/Mild, where a ton covers 650 sq ft, and shrink by a fifth on Cold, where it covers 390. For one room or one zone, our mini split heat pump sizing calculator is the better tool.

1.5 Ton Heat Pump Square Footage: What It Covers

A 1.5 ton heat pump (18,000 BTU) suits roughly 600 to 1,000 sq ft. That covers a small bungalow, a condo, or an addition running on its own system. In a mild climate with solid insulation it can stretch to the top of that range; in a cold zone it will struggle above about 800 sq ft.

2 Ton Heat Pump Square Footage: What It Covers

A 2 ton heat pump (24,000 BTU) generally covers 900 to 1,300 sq ft. This is a common size for smaller single-story homes. If the house sits at the upper end of that range and has large windows or a cold climate, the next size up is usually the safer call.

2.5 Ton Heat Pump Square Footage: What It Covers

A 2.5 ton heat pump (30,000 BTU) fits roughly 1,000 to 1,500 sq ft. It is the usual step between a small home and the 1,500 sq ft mainstream, and it is often the right answer for a well-insulated 1,500 sq ft house in a mixed climate.

3 Ton Heat Pump Square Footage: What It Covers

A 3 ton heat pump (36,000 BTU) covers about 1,200 to 2,000 sq ft, which makes it the most commonly installed residential size. A 1,500 sq ft home in a mixed climate typically lands here. Pushing it toward 2,000 sq ft only works with good insulation and a moderate climate.

3.5 Ton Heat Pump Square Footage: What It Covers

A 3.5 ton heat pump (42,000 BTU) suits roughly 1,500 to 1,900 sq ft. It is the half-step that stops a 3 ton unit running flat out in a colder zone without jumping to a 4 ton system that would short-cycle in shoulder season.

4 Ton Heat Pump Square Footage: What It Covers

A 4 ton heat pump (48,000 BTU) covers about 1,800 to 2,500 sq ft. At this size, duct capacity starts to matter as much as the equipment: undersized ductwork will cap what the unit can actually deliver no matter what the nameplate says.

5 Ton Heat Pump Square Footage: What It Covers

A 5 ton heat pump (60,000 BTU) handles roughly 2,400 to 3,000 sq ft, and it is the largest single residential unit commonly sold. Above 3,000 sq ft the answer is usually two systems or a zoned setup rather than one larger machine, and a Manual J calculation stops being optional.

What Factors Affect Heat Pump Size?

Many factors beyond square footage affect the correct heat pump size. Here are the most important ones, and all are incorporated into our calculator:

• Climate Zone: Colder climates need more BTU per square foot because the temperature difference between indoors and outdoors is greater.
• Insulation & Air Sealing: A well-insulated, tightly sealed home retains heat much better and needs a smaller heat pump. A leaky, poorly insulated home loses heat rapidly, requiring more capacity.
• Ceiling Height: Higher ceilings mean more air volume to heat and cool. A home with 10-ft ceilings has 25% more air volume than the same floor area with 8-ft ceilings.
• Windows & Sun Exposure: Large windows, especially facing south and west, gain significant solar heat. More window area also means more heat loss in winter.
• Ductwork Condition: Leaky ducts in unconditioned spaces (attics, crawlspaces) can waste 20-30% of conditioned air, effectively increasing the required equipment capacity.
• Home Layout / Stories: Two-story homes have more exterior wall area than single-story homes with the same square footage. Open-plan designs may need slightly more capacity for air distribution.
• Humidity & Cooling Load: Humid climates require more cooling capacity for proper dehumidification. Oversizing in humid climates is especially problematic.
• Very Cold Winter Temperatures: In extreme cold, a heat pump's output drops. Backup heat strategy and cold-climate-rated equipment become essential.
• Existing System Efficiency: Your old furnace or AC size is not a reliable guide for your new heat pump size. Older systems were frequently oversized.

The cheapest ton is the one you never have to buy. On the calculator, a 2,000 sq ft house on Mixed/Humid comes to about 56,900 BTU with poor insulation, 49,400 with average, 44,500 with good and 40,500 with excellent. Going from poor to good removes about 12,400 BTU, a full ton of equipment.

If the attic is thin or the house is drafty, air seal and insulate first, then size the heat pump for the house you end up with.

Oversized vs Undersized Heat Pumps

If a Heat Pump Is Too Big

• Short cycling: The unit reaches the set temperature too quickly and shuts off, then restarts shortly after. This constant on-off cycling wastes energy and increases wear.
• Weak dehumidification: In cooling mode, short run times prevent adequate moisture removal from the air, leading to a clammy, uncomfortable home.
• Reduced comfort: Temperature swings become wider, and some rooms may not get adequate airflow.
• Lower efficiency: Heat pumps are least efficient during startup. Frequent cycling reduces overall seasonal efficiency.
• More wear: Each start-stop cycle stresses compressor components, potentially reducing equipment lifespan.

If a Heat Pump Is Too Small

• Runs constantly: The unit can't keep up with the heating or cooling demand, especially during extreme weather.
• Struggles in extreme weather: Comfort drops significantly during the coldest or hottest days of the year.
• Backup heat runs more often: Electric resistance backup heat is far more expensive to operate, driving up bills.
• Higher bills: Constant running plus backup heat use leads to unnecessarily high energy costs.
• Poor comfort: The home may never fully reach the desired temperature.

The key takeaway: bigger is not better. And replacing your old system with the same size - a “like-for-like replacement” - can be wrong if the original system was oversized, which is common with older equipment.

Size is only half of it, though. A correctly sized heat pump still underperforms if the ducts cannot move the air it was designed around, so once you have the tonnage, check the airflow it implies with our system airflow calculator before you commit to equipment.

Heat Pump Size for Cold Climates

In cold and very cold climates, heat pump sizing is more complex than in milder regions. The key issues are:

• Nominal size alone is not enough. A 3-ton heat pump doesn't deliver 36,000 BTU of heating when it's -10°F outside. Heating output drops as outdoor temperatures fall.
• Low-temperature heating capacity matters. Look for the heat pump's rated heating output at 5°F or 17°F, not just at the standard 47°F test condition.
• Backup heat strategy is essential. Most cold-climate installations need a backup heat source - either electric resistance strips or a dual-fuel setup with a gas furnace.
• Don't just size way up. Oversizing to compensate for cold weather creates the same short-cycling and dehumidification problems. Instead, choose a cold-climate-rated unit with verified low-temperature performance.
• Design outdoor temperature matters. Your local design temperature - the coldest temperature your area typically experiences - should drive the sizing conversation with your contractor.
• Cold-climate-rated models may be necessary. ENERGY STAR specifically certifies cold-climate heat pumps that are tested for low-temperature operation.

Mini Split vs Central Heat Pump Sizing

Sizing a central (ducted) heat pump is different from sizing a ductless mini split system:

• Central systems are sized for the whole home's total heating and cooling load, then the ductwork distributes conditioned air to every room.
• Mini split systems are often sized zone-by-zone or room-by-room. Each indoor head unit is matched to the specific load of its area.
• One large ductless unit is not always the answer. A single 3-ton mini split in a living room won't adequately heat or cool bedrooms with closed doors.
• Multi-zone mini split systems connect multiple indoor units to one outdoor compressor. Each zone should be independently sized.

Our calculator above is designed for whole-home central sizing. If you need ductless or mini split sizing, use our mini split heat pump sizing calculator instead, which works zone by zone and snaps the result to the nominal ductless capacities these units are actually sold in. For a single room or a rental where a permanent install is not an option, a window heat pump drops into the sash and covers both seasons for that one room.

Heat Pump vs Air Conditioner: What Changes in the Size

A heat pump is an air conditioner that can also run backwards, so in cooling the two are sized the same way. The difference is winter. An air conditioner is sized for the cooling load only, while a heat pump has to cover whichever load is bigger.

Take a 2,000 sq ft house. In a cold climate our AC sizing gives 3 tons, and this calculator gives 5 tons or more for a heat pump in the same house, because heating is the bigger job there. In a hot and humid climate both land between 4 and 5 tons.

So heat pump vs air conditioner sizing only differs where winters are cold. In the South, replace an AC with a heat pump of the same tonnage. In the North, expect a bigger heat pump than the AC it replaces, and use the balance point check above to decide how much bigger. For heat pump vs AC or heat pump vs central air sizing, that is the whole answer: the same tonnage in the South, bigger in the North.

The Difference Between a Heat Pump and an Air Conditioner

One part separates them, the reversing valve. It lets the outdoor unit swap jobs, so the machine that pushes heat out of the house in July pulls heat into it in January. That is the whole difference between heat pump and air conditioner: an AC only runs one way. AC vs heat pump, heat pump versus air conditioner, heat pump vs AC unit and central AC vs heat pump all come down to that one valve.

On efficiency the answer splits by season. Are heat pumps more efficient than air conditioners in cooling? No. Two units with the same SEER2 rating use the same electricity to cool the same house. The gain comes in winter, when a heat pump moves heat instead of making it and so beats the electric resistance heat that an AC and air handler pair falls back on.

A few of these comparisons are not really choices. Take heat pump vs HVAC: a heat pump is one kind of HVAC system. Or condensing unit vs heat pump: the outdoor half of an AC is a condensing unit, and a heat pump's outdoor unit does that job plus heating. With air handler vs heat pump, the air handler is the indoor half, and a heat pump needs one too. For what a ducted heat pump costs to put in, see the HVAC replacement cost calculator.

Heat Pump vs Gas Furnace Size and Cost Considerations

If you're replacing a gas furnace with a heat pump, understand that the two systems are sized and rated very differently:

• Furnace size ≠ heat pump size. A 100,000 BTU furnace at 80% efficiency delivers 80,000 BTU to your home. A heat pump's delivered capacity varies with outdoor temperature, so a direct comparison isn't straightforward.
• Operating cost depends on many factors: local electricity rates, gas prices, climate, insulation, and how often backup heat runs.
• Don't copy the old furnace size blindly. Older furnaces were frequently oversized, and replacing with the same capacity heat pump will likely result in oversizing.

A dedicated heat pump vs gas furnace cost comparison calculator can help you evaluate the financial trade-offs for your specific situation. For the furnace side of that comparison, see the new furnace cost by size and efficiency.

When to Get a Manual J or Professional Heat Loss Calculation

While our calculator provides a solid estimate, there are situations where a professional Manual J calculation is strongly recommended:

• Your home has poor insulation or known air leakage problems
• Your ductwork is leaky or runs through unconditioned spaces
• You have high or vaulted ceilings (10 ft or more)
• Your home has large window areas or significant south/west glass exposure
• You live in a cold or very cold climate
• Your home has an unusual layout or additions
• You're receiving conflicting quotes from different contractors
• Your calculator result falls between two nominal equipment sizes
• You want to remove fossil fuel backup entirely and go all-electric

For more information, see these industry resources:

• ✦ENERGY STAR® Air Source Heat Pumps Guide
• ✦Trane: Understanding Heat Pump Sizing
• ✦Carrier: Heat Pump Systems & Capacities

A proper Manual J gives room-by-room load data, which helps size equipment precisely and design ductwork correctly. A good contractor should base their recommendation on detailed home measurements, not a quick eyeball or a rule of thumb.

Checking the Size on a Contractor's Quote

Three quotes with three different tonnages is normal, and it is the usual reason people start determining heat pump size on their own. The calculator has an optional field for this. Enter the size you were quoted and it tells you whether the quote is broadly aligned with its estimate, more than 20% over it, or more than 15% under it.

Then put two heat pump questions to each contractor. Is this unit sized to the heating load or the cooling load? And what is its output at 17°F, with what backup heat covering the rest? What the load report itself should show is covered in our guide on how to get a Manual J done.

A quote that arrives with those answers can be trusted over this estimate. One that arrives with neither is a guess, whatever the tonnage.

References & Methodology Sources

• ENERGY STAR: Air Source Heat Pumps
• Trane: Heat Pump Sizing Guide
• Carrier: Residential Heat Pumps
• Our Math Engine: See The Sizing Methodology Guide