What size heat pump do I need for a 1,800 sq ft house?

About 3 to 5 tons. In a mixed climate like Atlanta the estimate is 3 tons (cooling load 32,100 BTU/h, heating load 34,200 BTU/h). Hot climates need more cooling capacity and cold climates more heating capacity, as the table shows.

How many BTU do I need for 1,800 square feet?

For cooling, roughly 35,100 BTU/h in a hot, dry climate and 27,600 BTU/h in a cold one. For heating, from 27,000 to 54,000 BTU/h depending on how cold winters get. Older, drafty homes need up to 30% more.

Is it better to oversize or undersize a heat pump?

Neither, but slight undersizing is usually less harmful for cooling. An oversized unit short-cycles and leaves the air clammy. In cold climates, size for the heating load and check the unit’s output at 5°F, or plan for backup heat on the coldest nights.

What size heat pump for a 1,800 sq ft house?

Short answer: 3 to 5 tons, depending on your climate and insulation. In a mixed climate like Atlanta: 3 tons.

By climate

Hot and dry (Phoenix)3 ton
Hot and humid (Houston)3 ton
Mixed (Atlanta)3 ton
Cold (Chicago)4 ton
Very cold (Minneapolis)5 ton

Average insulation, 8 ft ceilings, three occupants.

Best 3-ton heat pumps

Most efficient

TOSHIBA CARRIER MCY-MUB0368HS2P-UL

3 ton central · cold-climate certified

SEER2: 29.7
HSPF2: 12.2
Heat at 5°F: 28,200

Top-rated certified model in the size most 1,800 sq ft homes need.

Full specs and running cost

Best for cold winters

Lennox EL21KLV-036-230A

3 ton central · Elite EL21KLV SERIES · cold-climate certified

SEER2: 20.0
HSPF2: 10.4
COP at 5°F: 2.48

Cold-climate certified, best efficiency at 5°F in this size.

Full specs and running cost

Compare all 3-ton heat pumps

Work it out for your home

Pre-filled with 1,800 sq ft. Pick your city and adjust insulation, sun and ceiling height.

Your space

Area to heat and cool sq ftCeiling heightInsulationSun exposurePeople who usually use itIncludes the kitchen?

Your climate

StateCity

Mini-split size: 36,000 BTU
Central / ducted size: 3 ton
Cooling load: 35,100 BTU/h
Heating load: 27,000 BTU/h

See 36,000 BTU mini-splits See 3-ton central heat pumps

Rule-of-thumb estimate: cooling follows the ENERGY STAR room sizing table, heating uses typical BTU per square foot for the climate (NOAA 1991-2020 heating degree days). For a whole-house system, ask your installer for a Manual J load calculation.

More detail

Cooling and heating loads by climateBTU/h

Hot and dry (Phoenix)cooling 35,100 · heating 27,000
Hot and humid (Houston)cooling 35,100 · heating 27,000
Mixed (Atlanta)cooling 32,100 · heating 34,200
Cold (Chicago)cooling 30,600 · heating 48,600
Very cold (Minneapolis)cooling 27,600 · heating 54,000

Cooling follows the ENERGY STAR sizing table; heating uses BTU per sq ft for the climate (NOAA 1991-2020 normals).

How insulation changes the sizein Atlanta

Poor4 ton · heating 44,500 BTU/h
Average3 ton · heating 34,200 BTU/h
Good2.5 ton · heating 27,400 BTU/h
Very good2.5 ton · heating 22,200 BTU/h

Top 5 3-ton heat pumpsranked by SEER2

#	Model	SEER2	EER2	HSPF2	COP at 5°F
1	TOSHIBA CARRIER MCY-MUB0368HS2P-UL	29.7	17.2	12.2	2.42
2	LG KUSXA361A	23.5	13.7	10.5	2.16
3	Carrier 27VNA336A*030also sold as 1 other model number	22.5	12.5	9.5	2.10
4	Comfortmaker C5H3V36KAAA	22.5	12.5	9.5	2.14
5	Heil H5H3V36KAAA	22.5	12.5	9.5	2.14

Questions3

What size heat pump do I need for a 1,800 sq ft house?: About 3 to 5 tons. In a mixed climate like Atlanta the estimate is 3 tons (cooling load 32,100 BTU/h, heating load 34,200 BTU/h). Hot climates need more cooling capacity and cold climates more heating capacity, as the table shows.
How many BTU do I need for 1,800 square feet?: For cooling, roughly 35,100 BTU/h in a hot, dry climate and 27,600 BTU/h in a cold one. For heating, from 27,000 to 54,000 BTU/h depending on how cold winters get. Older, drafty homes need up to 30% more.
Is it better to oversize or undersize a heat pump?: Neither, but slight undersizing is usually less harmful for cooling. An oversized unit short-cycles and leaves the air clammy. In cold climates, size for the heating load and check the unit’s output at 5°F, or plan for backup heat on the coldest nights.

Other sizes

All sizing guides