What Size AC for a 600 Square Foot Apartment?
Cooling load
16,000 BTU/hr
600 square feet, 8 foot ceilings, climate zone 4, average sun, two people, kitchen inside.
This is a rule of thumb and it is not a load calculation. The real answer is a Manual J, which counts your windows, your insulation, your infiltration and which way the house faces, and a contractor should run one before anybody orders equipment. Use this number to sanity check a quote, not to place an order.
Oversizing is the classic mistake and it is worse than being slightly small. A unit with too much capacity satisfies the thermostat in a few minutes and shuts off, so it never runs long enough to pull water out of the air, and the house ends up cold and clammy with the compressor short cycling itself to an early grave.
When the figures look right, the HVAC equipment list downloads as a real PDF with your business details on it, built inside your own browser. Nothing you type is uploaded anywhere.
How that number is worked out
These are the figures this page was built with and every line the calculator produces from them. Change anything above and all of it moves.
- Conditioned floor area600 sq ft
- Ceiling height8 ft
- Climate zoneZone 4, mixed, mid Atlantic and the lower Midwest
- Sun exposureAverage
- People living there2 each
- Kitchen inside the conditioned spaceYes
Cooling size1.5 tons
This is a rule of thumb and it is not a load calculation. The real answer is a Manual J, which counts your windows, your insulation, your infiltration and which way the house faces, and a contractor should run one before anybody orders equipment. Use this number to sanity check a quote, not to place an order.
Oversizing is the classic mistake and it is worse than being slightly small. A unit with too much capacity satisfies the thermostat in a few minutes and shuts off, so it never runs long enough to pull water out of the air, and the house ends up cold and clammy with the compressor short cycling itself to an early grave.
| Cooling load | 16,000 BTU/hr |
|---|---|
| That is | 1.33 tons12,000 BTU makes a ton |
| Equipment size to shop for | 1.5 tonnearest half ton step |
| Cooling per square foot | 27 BTU |
| Heating output needed | 27,000 BTU/hr |
| Furnace input, 80% AFUE | 33,750 BTU/hr |
| Furnace input, 95% AFUE | 28,421 BTU/hr |
The material list this produces
| Condenser, tons | 2 |
|---|---|
| Matched air handler or coil, tons | 2 |
| Line set, ft | 25 |
| Equipment pad, each | 1 |
| Disconnect and whip, each | 1 |
| Programmable thermostat, each | 1 |
Climate zone compared
The same house sizes differently by climate, and not in the direction people expect. Cooling load falls as you go north while heating load climbs, so a Minnesota house needs a smaller air conditioner and a much bigger furnace than a Florida one.
| Climate zone | Cooling size | Heating output needed |
|---|---|---|
| Zone 1 | 1.5 tons | 18,000 BTU/hr |
| Zone 2 | 1.5 tons | 21,000 BTU/hr |
| Zone 3 | 1.5 tons | 24,000 BTU/hr |
| Zone 4 | 1.5 tons | 27,000 BTU/hr |
| Zone 5 | 1.5 tons | 30,000 BTU/hr |
| Zone 6 | 1.5 tons | 33,000 BTU/hr |
| Zone 7 | 1 ton | 36,000 BTU/hr |
What else matters here
Sixteen thousand BTU, and 4,000 of that is the kitchen. On a small apartment the kitchen allowance is a quarter of the whole load, which is why studios and one bedrooms come out at a much higher BTU per square foot than houses do. This one is 27 a square foot against the 23 a 2,000 square foot house gets.
The practical answer is a 1.5 ton system, or a multi head mini split with one head in the living space and one in the bedroom. A single head trying to serve a bedroom through a doorway will leave that bedroom warm regardless of its capacity, because air does not go around corners on its own.
In an apartment the thing you usually cannot change is the window. If the unit has to be a window air conditioner, measure the opening before shopping, because the 18,000 BTU units are physically much larger than the 12,000 ones and plenty of them do not fit a standard double hung.
What this calculator assumes
- This is the square foot method, the same rule of thumb behind every free sizing chart: 20 BTU per square foot of cooling as the base, scaled for ceiling height, climate zone and sun, plus 600 BTU for each person over two and 4,000 for a kitchen.
- Heating is figured at 30 to 60 BTU per square foot depending on zone, which is output at the register. Furnace input is higher, because an 80 percent furnace throws a fifth of the gas up the flue.
- Equipment is sold in half ton steps up to 5 tons, so the number to shop with is the rounded one, not the raw one.
Questions people ask
How many BTU for a 600 square foot apartment?
About 16,000 with a kitchen inside the space, which is a 1.5 ton system. Without a kitchen it drops to around 12,000.
Why does a small apartment need more BTU per square foot?
Because the fixed loads do not shrink. A kitchen adds about 4,000 BTU whether it sits in 600 square feet or 3,000, and on a small space that is a quarter of the total.
Is it better to go one size up?
No, and this is the most common mistake in residential HVAC. An oversized unit cools the air fast, satisfies the thermostat and shuts off before the coil has been cold long enough to pull moisture out. You get a house that is cold and clammy, and a compressor that short cycles its way to an early death. A slightly small system just runs longer on the hottest afternoon of the year.
The btu and ac size calculator takes any dimensions you like and hands back the same list.