What Size AC for a 2,000 Square Foot House?
Cooling size
4 tons
2,000 square feet, 8 foot ceilings, climate zone 4, average sun, four 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.
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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 area2000 sq ft
- Ceiling height8 ft
- Climate zoneZone 4, mixed, mid Atlantic and the lower Midwest
- Sun exposureAverage
- People living there4 each
- Kitchen inside the conditioned spaceYes
Cooling size4 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 | 45,200 BTU/hr |
|---|---|
| That is | 3.77 tons12,000 BTU makes a ton |
| Equipment size to shop for | 4 tonnearest half ton step |
| Cooling per square foot | 23 BTU |
| Heating output needed | 90,000 BTU/hr |
| Furnace input, 80% AFUE | 112,500 BTU/hr |
| Furnace input, 95% AFUE | 94,737 BTU/hr |
The material list this produces
| Condenser, tons | 4 |
|---|---|
| Matched air handler or coil, tons | 4 |
| 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 | 4.5 tons | 60,000 BTU/hr |
| Zone 2 | 4 tons | 70,000 BTU/hr |
| Zone 3 | 4 tons | 80,000 BTU/hr |
| Zone 4 | 4 tons | 90,000 BTU/hr |
| Zone 5 | 3.5 tons | 100,000 BTU/hr |
| Zone 6 | 3.5 tons | 110,000 BTU/hr |
| Zone 7 | 3.5 tons | 120,000 BTU/hr |
What else matters here
Forty five thousand two hundred BTU, 3.77 tons, rounding to 4. Twenty three BTU a square foot, which is where a normally insulated house in a mixed climate sits.
A house this size is where zoning starts to be worth discussing. Four tons through one thermostat in a two story house will leave the upstairs warm and the downstairs cold all summer, because the load is not where the thermostat is. Two systems, or one system with a zone damper and a second sensor, fixes a problem that no amount of extra tonnage will.
Ninety thousand BTU of heating output means a 112,500 input furnace at 80 percent AFUE. Note how much bigger that input number is than the output: a fifth of the gas an 80 percent furnace burns goes up the flue, which is the whole argument for the 95 percent unit if the fuel price where you are makes it pay.
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 2,000 square feet?
About 45,200 for cooling in a mixed climate, which is a 4 ton system. Hotter zones push it toward 49,000, colder ones down toward 41,000.
Do I need one system or two for 2,000 square feet?
One will do it on a single story. On two floors, one system and one thermostat usually means an uncomfortable upstairs, and the fix is zoning or a second system rather than more tonnage.
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.