These are the standard AC unit sizes for a house, and each goes by several names. A 3 ton AC unit moves 36,000 BTU of heat an hour, and a 3 ton air conditioner or a 3 ton AC system on a quote means exactly that capacity. A 3 ton air conditioning unit, or a three ton AC unit, is one piece of equipment: an outdoor unit and an indoor coil rated to move that 36,000 BTU. The same holds for a 2 ton AC unit at 24,000 BTU and a 4 ton AC unit at 48,000 BTU. Each size has its own section below with the room it covers, the airflow it needs and the circuit it runs on.
Why Coverage Is a Range and Not a Number
Every row above gives square footage as a span rather than a figure, and the span is wide on purpose. A 3 ton unit covers 1,400 sq ft in one house and 1,900 in another, and both are correct.
Climate does most of that work. The same house needs materially more cooling on the Gulf coast than in the upper Midwest, so the low end of each range is the hot and humid answer and the high end is the northern one. After climate, the things that move it are insulation quality, window area and orientation, ceiling height, how many people live there, and whether the house is one story or two.
Use the table to understand what a size means, not to pick one. If you already own a system and just want to confirm its size, you can read the tonnage off its model number. If you are choosing rather than checking, run the actual numbers with the AC tonnage per square foot calculator for a whole house, or the HVAC load calculator for a room-by-room load. Sizing just one room? Use Tonnage Calculator AC, which gives that room's load in BTU and tons. Roughly half of installed systems are oversized, and the cost of guessing high is paid every month afterwards. When a correctly sized system still falls behind, size is rarely the cause, and the guide on why an AC runs without cooling covers what to check.
The same caveat applies to the price column, and it is worth stating plainly because a single dollar figure looks more certain than it is. Each price above is a national midpoint for a straightforward like-for-like swap at a mid efficiency tier. Three things move it a long way in either direction: the efficiency tier you pick, which can add close to half again on the equipment; your region, since the same job runs materially more in high-cost metros than in the rural south; and whether any ductwork or electrical work is needed, which is the line item that most often separates two quotes for what looks like identical work. To put your own numbers against a size, the central air installation cost calculator breaks a central AC job into those line items, and the installation and replacement cost calculators cover the other jobs if the furnace or the ductwork is changing at the same time.
1.5 Ton AC Unit
The smallest standard central size: about $4,500 installed, moving 600 CFM through a 12-inch supply trunk and drawing roughly 1,440 watts, or 6 amps at 240V. It suits about 600 to 950 sq ft depending on climate. At this size the honest question is whether central air is the right product at all. A small house, a large apartment or a finished basement in this range is often better served by a ductless head, which avoids running ductwork for a load this small. A 1.5 ton air conditioner is also written as a 1 1/2 ton AC unit, and it is rated at 18,000 BTU.
2 Ton AC Unit
Two tons costs about $5,000 installed, needs 800 CFM through a 14-inch supply and a 16-inch return, and pulls around 1,920 watts at 8 amps - a fit for about 900 to 1,300 sq ft. This is the size people most often discover they already have and then start doubting, usually after one hot week. Before concluding it is undersized, check the ductwork and the air sealing: a 2 ton unit struggling in a 1,100 sq ft house is far more often a duct or infiltration problem than a capacity one. Note that air conditioning units 2 ton and up are all sold on the same nominal scale, so a 2 ton air conditioner from one maker and another from a different one cover the same load even when the cabinets look nothing alike. A 2 ton air conditioning unit, a 2 ton AC system, a two ton AC unit and a 2 ton central air unit are four names for this one size, 24,000 BTU.
2.5 Ton AC Unit
Roughly $5,500 installed, moving 1,000 CFM through a 16-inch supply and drawing about 2,400 watts, 10 amps - a fit for about 1,150 to 1,600 sq ft. Two and a half tons is the usual answer for a mid-size single-story home, and it is the step where ductwork starts mattering more than tonnage. It is also the size most often skipped in a quote, because a contractor who stocks 2 and 3 ton units will tend to push you to whichever is on the truck. Listings write it three ways, 2.5 ton AC unit, 2 1/2 ton AC unit and 2.5 ton air conditioning unit, and all of them mean 30,000 BTU.
3 Ton AC Unit
The most common central AC size in American homes: about $6,000 installed or $79 a month financed, 1,200 CFM through a 16-inch supply and an 18-inch return, drawing 2,880 watts at 12 amps. It suits about 1,400 to 1,900 sq ft.
Being the default size is exactly the problem with it. A 3 ton air conditioner is what gets quoted when nobody has run a load calculation, so it is both the most correct size in America and the most frequently wrong one. Its startup surge of 8,600 to 14,400 watts is also the point where generator backup stops being simple, which is why soft-start kits are most often fitted at this size. You will see it sold as a 3.0 ton AC unit, a three ton air conditioner, a 3 ton air conditioning system or a 3 ton central air unit. A 3 ton condenser is the outdoor half of the same system.
3.5 Ton AC Unit
Roughly $6,700 installed, needing 1,400 CFM through an 18-inch supply and a 20-inch return, drawing 3,360 watts at 14 amps - and covering about 1,650 to 2,250 sq ft. This size does not exist in every product line, which is why some quotes jump straight from 3 to 4 tons. It is worth asking for specifically, because taking the 4 ton instead means paying more up front and then running an oversized system for its whole life. A 3.5 ton air conditioning unit and a 3.5 ton air conditioning system are the same 42,000 BTU machine, sometimes listed as 3 1/2 tons.
4 Ton AC Unit
Four tons runs about $7,400 installed, moving 1,600 CFM through a 20-inch supply and a 22-inch return, drawing 3,840 watts at 16 amps - a fit for about 1,900 to 2,600 sq ft. The ductwork is the constraint that bites here. Plenty of houses that could use 4 tons have trunks sized years ago for 3, and dropping the larger unit onto the smaller duct produces register noise and starved far rooms rather than more cooling. A two-story house of this footage also usually does better with zoning than with one larger system. The names follow the same pattern as the smaller sizes: 4 ton AC system, 4 ton air conditioning unit, four ton AC unit and 4.0 ton AC unit, all 48,000 BTU.
5 Ton AC Unit
The largest standard residential size: about $8,500 installed, needing 2,000 CFM through a 22-inch supply and a 24-inch return, drawing 4,800 watts at 20 amps, and suiting about 2,400 to 3,300 sq ft. Above five tons you leave the residential product range and into light commercial equipment, which is why large houses are more often served by two systems than one bigger one. Two smaller units also give you zoning for free and mean a failure takes out half the house rather than all of it. If a contractor is quoting a 5 ton air conditioner for a house under about 2,400 sq ft, ask to see the load calculation before agreeing, because at this size an oversizing mistake is an expensive one to live with. A 5 ton air conditioning unit, a 5 ton AC system, a five ton AC unit and a 5.0 ton air conditioner are one size, 60,000 BTU.
Condenser, Coil and Air Handler: What an AC Unit of Each Size Includes
A price or a spec for a 3 ton AC unit can mean three different amounts of equipment, and quotes differ by thousands because of it. Knowing which pieces are included is worth more than any number in the table.
- The condenser. The outdoor cabinet with the compressor and the fan. A 3 ton condenser or 3 ton condenser unit is only this half. It cannot cool anything without a coil indoors.
- The evaporator coil. The indoor half, sitting on top of the furnace. It has to be matched to the condenser, which is why a proper replacement changes both.
- The air handler. A cabinet holding the coil and a blower, used when there is no furnace. A 3 ton AC unit and air handler together is a complete electric system, and a 3 ton air handler alone is the indoor half.
- A package unit. All of the above in one outdoor cabinet, connected to the house only by ducts. A 3 ton package unit sits on a slab or the roof and is common on mobile homes and in the South.
The same four terms apply at every size, so a 4 ton condenser, a 5 ton air handler and a 2 ton package unit all follow this pattern. Every figure in the table at the top is for a split system: condenser and matched indoor coil, installed on existing ducts.
Tip: when two quotes for one tonnage are far apart, check that both list the same pieces before you compare the prices. A heat pump of the same tonnage has the same cooling capacity and adds heating, and the heat pump size calculator sizes that side. For the floor area each size covers in your climate, see AC tons to square feet by climate.
What the Ton Actually Measures
One ton equals 12,000 BTU per hour of cooling, so a 3 ton unit removes 36,000 BTU of heat every hour it runs. The name is a leftover from the ice trade: it is the cooling you would get from melting one ton of ice over 24 hours. It says nothing about the physical weight of the equipment, which is a reasonable thing to assume and a common source of confusion. If you need to move between the two units at any size, the ton to BTU converter lists every step.