What size mini-split do I need for 600 square feet?

About 15,000 to 18,000 BTU. In a mixed climate like Atlanta the estimate is 15,000 BTU (cooling load 15,300 BTU/h, heating load 11,400 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 600 square feet?

For cooling, roughly 16,700 BTU/h in a hot, dry climate and 13,200 BTU/h in a cold one. For heating, from 9,000 to 18,000 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 mini-split for 600 sq ft?

Short answer: 15,000 to 18,000 BTU, depending on your climate and insulation. In a mixed climate like Atlanta: 15,000 BTU.

By climate

Average insulation, 8 ft ceilings, three occupants.

Best 15,000 BTU mini-splits

Most efficient

Fujitsu AOUH15KTAP1

15,000 BTU mini-split · AIRSTAGE H-Series · cold-climate certified

SEER2: 28.7
HSPF2: 13.0
Heat at 5°F: 18,400

Top-rated certified model in the size most 600 sq ft rooms need.

Full specs and running cost

Best for cold winters

Fujitsu AOUH15KTAP1

15,000 BTU mini-split · AIRSTAGE H-Series · cold-climate certified

SEER2: 28.7
HSPF2: 13.0
COP at 5°F: 2.52

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

Full specs and running cost

Compare all 15,000 BTU mini-splits

Work it out for your room

Pre-filled with 600 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: 18,000 BTU
Central / ducted size: 1.5 ton
Cooling load: 16,700 BTU/h
Heating load: 9,000 BTU/h

See 18,000 BTU mini-splits See 1.5-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 16,700 · heating 9,000
Hot and humid (Houston)cooling 16,700 · heating 9,000
Mixed (Atlanta)cooling 15,300 · heating 11,400
Cold (Chicago)cooling 14,600 · heating 16,200
Very cold (Minneapolis)cooling 13,200 · heating 18,000

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

Poor18,000 BTU · heating 14,800 BTU/h
Average15,000 BTU · heating 11,400 BTU/h
Good15,000 BTU · heating 9,100 BTU/h
Very good15,000 BTU · heating 7,400 BTU/h

Top 5 15,000 BTU mini-splitsranked by SEER2

#	Model	SEER2	EER2	HSPF2	COP at 5°F
1	Fujitsu AOUH15KTAP1	28.7	15.4	13.0	2.52
2	Fujitsu AOUH15KZAH1	27.5	14.8	12.7	2.10
3	Century A-ZHP15SA-1	27.0	13.0	11.0	2.00
4	MDV MOX430-15HFN10-M1Halso sold as 2 other model numbers	27.0	13.0	11.0	2.00
5	Mitsubishi Electric MUZ-FX15NLHZalso sold as 1 other model number	25.9	14.7	11.0	2.06

Questions3

What size mini-split do I need for 600 square feet?: About 15,000 to 18,000 BTU. In a mixed climate like Atlanta the estimate is 15,000 BTU (cooling load 15,300 BTU/h, heating load 11,400 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 600 square feet?: For cooling, roughly 16,700 BTU/h in a hot, dry climate and 13,200 BTU/h in a cold one. For heating, from 9,000 to 18,000 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