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AC size · 2,800 sq ft
What size AC for a 2,800 sq ft house
A 2,800 sq ft house needs anywhere from 1.5 tons to 6 tons of cooling in the 14 climates below. The low end is a tight 2015 house in Seattle, WA and the high end is a 1985 house with attic ducts in Phoenix, AZ. At the high end 6 tons is a load, not a unit you can order. The 400 to 600 sq ft per ton rule gives 4.67 to 7 tons for all of them, and its top end is past 5 tons, the largest size in the residential ducted lineup this calculator sizes against. Check your zone first.
Run your own house in the calculator. It starts with a 2,800 sq ft two-story house in Atlanta, GA, built in 1985 with ducts in the attic.
- Type the 5-digit ZIP of the job. The calculator looks up the climate zone and its design temperatures.
- Enter the conditioned floor area, stories and year built. The form starts at 2,800 sq ft.
- Pick air tightness, foundation and window type, and check the box if the ducts run through an unconditioned attic.
- Read the cooling load and tonnage, then find the row for your climate zone in the table below to see how the envelope changes the size.
Example result for the default inputs
ZIP 30303 · Fulton County, GA · IECC zone 3A · elevation 1,001 ft · design 95°F DB / 76°F WB cooling, 18°F heating
Cooling load
39,803BTU/h
≈ 3.5 ton (nearest 0.5) · SHR 0.93
Heating load
50,411BTU/h
- Furnace input bin 80,000 BTU/h at 80% AFUE
- No single residential heat pump carries this heating load, so no heat pump size is shown
Load breakdown by component
| Component | Cooling | Heating |
|---|---|---|
| Transmission (walls, ceiling, floor, glass, doors) | 11,443 | 30,889 |
| Solar through glass | 18,163 | - |
| Infiltration | 3,302 | 11,120 |
| Internal gains (people, appliances) | 2,920 | - |
| Ducts in unconditioned attic | 3,975 | 8,402 |
- These design temperatures are the worst case for the IECC climate zone. BuildSolver estimates ZIP-level values can differ by 2-8°F.
- These are preliminary design conditions. For a permit load, take the design temperatures from ASHRAE Handbook - Fundamentals 2021, Chapter 14.
- A heat pump sized to carry this heating load alone would need 69,056 BTU/h of rated capacity at 47°F, more than one 5-ton residential unit delivers. Plan on furnace heat or a heat pump with furnace backup, and have an engineer check any all-electric design.
For estimation purposes only. Consult a licensed engineer for final designs.
Room-by-room Manual J and branded PDF reports · Pro plan
How the tonnage in the table is calculated
Each of the 28 cells in the table is its own run of the BuildSolver load engine on a 2,800 sq ft house, using the whole-house Speed Sheet simplification of ACCA Manual J 8th Edition. The AC size hub has the full method and every floor area side by side.
- House geometry
footprint = 2,800 / 2 = 1,400 sq ft; side = 37 ftThe engine models a square two-story footprint with 8 ft ceilings, which gives about 2,395 sq ft of gross wall and 1,400 sq ft of ceiling under the attic.- Tonnage
tons = Q_cool / 12,000, rounded to the nearest 0.5Loads are rounded to the nearest half ton, which puts this floor area between 1.5 tons and 6 tons.- Square feet per ton
sq ft per ton = 2,800 / (Q_cool / 12,000)Computed from the unrounded load. Across this table one ton covers 471 to 2,217 sq ft.
AC size for a 2,800 sq ft house in 14 climate zones
Each row is the same 2,800 sq ft two-story house on a slab with 4 occupants and glass at 15% of floor area. Only the climate zone and the envelope change. The first house column is a 1985 build with average air sealing and ducts in a vented attic. The second is a 2015 build with a tight envelope and ducts inside conditioned space. Tons are rounded to the nearest half ton. Each cell also shows the load in BTU/h and how many square feet one ton covers.
| Zone | Reference city | Cooling design | 1985 house, attic ducts | 2015 house, ducts inside |
|---|---|---|---|---|
| 1A | Miami, FL | 92°F | 4.5 tons55,453 BTU/h · 606 sq ft/ton | 2 tons26,759 BTU/h · 1,256 sq ft/ton |
| 2A | Houston, TX | 96°F | 5 tons59,064 BTU/h · 569 sq ft/ton | 2.5 tons28,576 BTU/h · 1,176 sq ft/ton |
| 2B | Phoenix, AZ | 110°F | 6 tons71,374 BTU/h · 471 sq ft/ton | 3 tons34,757 BTU/h · 967 sq ft/ton |
| 3A | Atlanta, GA | 95°F | 3.5 tons39,803 BTU/h · 844 sq ft/ton | 2 tons25,693 BTU/h · 1,308 sq ft/ton |
| 3B | Las Vegas, NV | 100°F | 3.5 tons42,565 BTU/h · 789 sq ft/ton | 2.5 tons27,756 BTU/h · 1,211 sq ft/ton |
| 3C | San Francisco, CA | 84°F | 2.5 tons27,754 BTU/h · 1,211 sq ft/ton | 1.5 tons17,848 BTU/h · 1,883 sq ft/ton |
| 4A | St. Louis, MO | 92°F | 3 tons35,910 BTU/h · 936 sq ft/ton | 2 tons23,343 BTU/h · 1,439 sq ft/ton |
| 4B | Albuquerque, NM | 95°F | 3 tons35,920 BTU/h · 935 sq ft/ton | 2 tons23,689 BTU/h · 1,418 sq ft/ton |
| 4C | Seattle, WA | 84°F | 2 tons22,944 BTU/h · 1,464 sq ft/ton | 1.5 tons15,156 BTU/h · 2,217 sq ft/ton |
| 5A | Chicago, IL | 91°F | 3 tons35,093 BTU/h · 957 sq ft/ton | 2 tons22,105 BTU/h · 1,520 sq ft/ton |
| 5B | Denver, CO | 93°F | 3 tons34,329 BTU/h · 979 sq ft/ton | 2 tons21,825 BTU/h · 1,540 sq ft/ton |
| 6A | Minneapolis, MN | 90°F | 2.5 tons31,805 BTU/h · 1,056 sq ft/ton | 1.5 tons20,463 BTU/h · 1,642 sq ft/ton |
| 6B | Billings, MT | 92°F | 2.5 tons31,482 BTU/h · 1,067 sq ft/ton | 1.5 tons20,459 BTU/h · 1,642 sq ft/ton |
| 7 | Duluth, MN | 86°F | 2 tons25,901 BTU/h · 1,297 sq ft/ton | 1.5 tons16,798 BTU/h · 2,000 sq ft/ton |
1 of the 28 sizes above is past 5 tons. Those numbers are loads, not equipment sizes, because the ducted lineup this calculator sizes against stops at 60,000 BTU/h.
Only 2 of the 28 engine results land inside the rule-of-thumb range of 4.67 to 7 tons, the 1985 house in zones 2A and 2B.
Phoenix, AZ splits the widest. The 1985 house with attic ducts needs 6 tons and the tight 2015 house with its ducts inside needs 3 tons, 3 tons apart on the same floor area.
Phoenix, AZ (71,374 BTU/h) puts the older house's cooling load at 65,000 BTU/h or more. DOE's residential central air conditioner rules cover units rated under 65,000 BTU/h, so a unit rated above that line is certified as commercial equipment. Plan on two residential systems for that house.
The highlighted Atlanta row is the calculator's starting point. There the 1985 house needs 39,803 BTU/h, or 3.5 tons, and a heating load of 50,411 BTU/h at 18°F. Built tight in 2015 with the ducts inside, the same house needs 2 tons. A 500 sq ft per ton quote would come to 5.5 tons for both, past the largest residential split system. Size each house from its own row, then check the existing ducts and registers before you write the quote.
Standards and data sources
- ACCA Manual J 8th Edition - residential load procedure. The tables use its whole-house Speed Sheet simplification, which gives a single load for the whole house.
- ACCA Manual S - equipment selection against the Manual J load, including the 115% limit on cooling capacity for a single-speed unit. Selection is a separate step and part of the Pro plan.
- IECC 2021 climate zones (PNNL county map) - ZIP to county to climate zone. The zone sets the design temperatures, solar factor and envelope defaults for each row.
What the table leaves out
- Every row is one standard 2,800 sq ft house. On a real job, insulation, glass, orientation and air leakage move the load, and in this table the 1985 and 2015 builds in Phoenix, AZ already land 3 tons apart.
- Each row uses the worst-case design temperature of its IECC climate zone, from 84°F in the San Francisco zone to 110°F in the Phoenix zone. BuildSolver estimates ZIP-level values can differ by 2-8°F, and ASHRAE Handbook - Fundamentals 2021, Chapter 14, lists the city values.
- The engine treats both stories as one zone. The page cannot split the load between floors, and a bonus room over a garage is not modeled.
- Whole-house load only. Room-by-room Manual J and Manual S equipment selection are part of the Pro plan.
Common sizing mistakes on a 2,800 sq ft house
- Quoting 5 tons because the house is 2,800 sq ft. The 400 sq ft per ton rule gives 7 tons here, more than residential ducted equipment carries, so a quote lands on 5 tons, the largest size in it. The rule hands the same answer to a 1985 build in Phoenix and a 2015 build in Seattle, because floor area is all it reads. The St. Louis, MO row puts the 1985 house at 3 tons and the 2015 house at 2 tons.
- Reusing the tonnage from a job in another market. Carry the Phoenix, AZ tonnage to a Seattle, WA job and you have sold 4 tons more equipment than the house asks for.
- Sizing off the nameplate of the unit coming out. It may have been picked by rule of thumb, and matching it repeats whatever oversizing the last installer chose.
- Letting the heating load set the AC. Duluth, MN asks the 1985 house for 82,841 BTU/h of heat and 2 tons of cooling. Pick the furnace and the AC from their own loads.
What to check on a 2,800 sq ft house
At 2,800 sq ft the listing, the tax record and what the system actually conditions rarely agree. These are two-story houses with four or five bedrooms, often with a finished basement or a room over the garage that the listing leaves out of the square footage. Measure the conditioned area yourself, then read the row for your zone.
- Enter the area the system conditions, not the number on the listing. A finished basement with supply registers belongs in the load. A sunroom on a window unit does not. At this size a 400 sq ft difference moves the answer half a ton or more in the hot rows.
- Two floors and a 50 ft run to the far bedroom put the static pressure problem ahead of the tonnage problem. Measure total external static on the system that is already there. A house this size piped with flex through a truss attic often cannot move the air the current unit is rated for, let alone a larger one.
- In the hot rows the 1985 column crosses into two-system territory while the 2015 column on the same line sits at about half of it. Before you quote two systems on an older house this size, price what sealing the attic ducts and bringing them inside conditioned space would do, because that one change is most of the distance between the columns.
Questions about AC size for 2,800 sq ft
What size AC do I need for a 2,800 sq ft house?
Climate and construction decide it. In the table on this page the answer runs from 1.5 tons in Seattle, WA to 6 tons in Phoenix, AZ. Chicago, IL puts the same house at 3 tons as a 1985 build and 2 tons as a 2015 build. Any size above 5 tons is a load, and residential ducted equipment stops at 5 tons, so that house takes two systems. Enter your ZIP and the house details in the calculator for your own number.
How many BTU does a 2,800 sq ft house need for cooling?
The cooling loads in the table run from 15,156 to 71,374 BTU/h. Per square foot that is 5.4 to 25.5 BTU/h, so no single BTU per square foot number fits a house this size. The top of that range is past the 5-ton limit on residential ducted equipment, so that house takes two systems. Run the actual house in the calculator above for its number.
Is a 5-ton AC too big for a 2,800 sq ft house?
The 400 sq ft per ton rule gives 7 tons here, past the 5-ton top of that lineup, so the largest unit a rule-of-thumb quote can land on is 5 tons. ACCA Manual S limits a single-speed cooling unit to 115% of the Manual J load. By that limit a 5-ton single-speed unit is oversized for the 1985 house in 11 of the 14 climates and for the 2015 house in 14 of them.
What size furnace goes with a 2,800 sq ft house?
The heating loads in the same runs go from 14,180 to 82,841 BTU/h, the highest for the 1985 house in Duluth, MN. With the engine's AFUE default for the year built, those loads call for furnace inputs from the 40,000 to the 120,000 BTU/h bin. The furnace size calculator shows the heating result for a single ZIP.
Why does a 2,800 sq ft house need a different size in Phoenix and Seattle?
Design temperature and solar load. The table uses 110°F for the Phoenix zone and 84°F for the Seattle zone, so the same 1985 house needs 6 tons in Phoenix and 2 tons in Seattle. The Phoenix number is past the 5-ton top of residential ducted equipment, so that job is two systems.
Can I quote a 2,800 sq ft job from this table?
Use it for the first conversation with the homeowner. Atlanta, GA puts the same 2,800 sq ft at 3.5 tons or 2 tons depending on how the house was built, so run the load for the actual house before you order equipment. Room-by-room Manual J and Manual S equipment selection are in the Pro plan. If the job needs a permit, ask the building department whether it requires a load report from ACCA-approved software.
Used on the same job
Size the actual house in chat
Start with the ZIP. Then describe the house you are quoting, including the windows, insulation and where the ducts run, and the assistant runs the same load tools, asks for what is missing and explains the result in terms you can show the homeowner.
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