4-ton AC unit cost

A 4-ton central air conditioner costs $5,600 to $12,000 installed, typically about $8,200, for the outdoor condenser and a matched indoor coil on the furnace and ducts you already have. Four tons is 48,000 BTU an hour of cooling, the size most often fitted to a larger two-story or a long ranch house.

What moves the price is less the condenser than everything it connects to. A 4-ton system has to push about 1,600 cubic feet of air a minute through the coil, the blower and the ducts, and in a house that used to have 3 tons, that is where the surprises are.

What it costs

The 4-ton figure assumes the furnace stays, the ducts stay, and the electrical circuit is already sized for the unit. When any of those three has to change, it is a separate line.

What house a 4-ton actually serves

The usual guide puts a 4-ton system at roughly 2,000 to 2,600 square feet, and in a cool climate or a tight, well-insulated house it can stretch toward 3,000. That spread is the whole point: the square footage is a starting guess, and the guess can be off by a full ton in either direction.

A 4-ton system tends to be the right answer in houses like these:

A 1990s or 2000s two-story of around 2,400 square feet in a hot or mixed climate, with a lot of glass on the south and west and the ducts in a vented attic.

A long single-story ranch where the attic ducts run hot and long, and the house has more exterior wall and roof per square foot than a compact two-story.

A house that has grown. An addition, a converted garage or a finished bonus room on an existing 3-ton system is the most common reason a homeowner is quoted 4 tons for the first time.

Residential condensers come in half-ton steps up to 4 tons, and the next common size above 4 is 5. That gap matters. A house that calculates at 4.2 tons is usually better served by a 4-ton unit than a 5-ton one, because a slightly undersized system on the very hottest afternoon is less harm than an oversized one every other day of summer.

Why the load calculation picks the size

A Manual J load calculation works out the heat a house gains on a design-temperature day, room by room: wall and attic insulation, window area and direction, air leakage, the number of people, and where the ducts run. It is the only method that tells you whether a house is a 3.5, a 4 or a 5.

Two things make it more than a formality on this size.

Nominal tons are not delivered tons. A unit sold as 4 tons is rated at test conditions. On a very hot day, with a particular coil and airflow, it delivers somewhat less. The manufacturer's expanded performance data shows how much, and a careful contractor reads it for your design temperature rather than trusting the number on the box.

Many 4-ton replacements are 3.5-ton houses. Systems installed decades ago were often sized by rule of thumb with a margin added, and replacing like for like copies the margin. If the load calculation comes back lower than the old nameplate, believe it. A smaller condenser costs less, dehumidifies better and runs quieter.

The cost by house size guide covers what each tonnage costs as a full system. This page is about whether 4 is the right one.

3, 4 or 5 tons: what the step costs

The typical 3-ton job is $6,800, the 4-ton $8,200, and the 5-ton $9,500. The equipment price climbs with each ton; the crew, the permit and the day barely move. So the step between sizes is modest, as long as the house around the unit can take it. Going up a ton in a house built for 3 is a different matter, for the reasons in the next section.

The coil, the blower and the ducts have to carry 1,600 CFM

Air conditioners are designed around roughly 350 to 450 cubic feet per minute of airflow per ton, which puts a 4-ton system near 1,600 CFM. In humid climates contractors often set it lower per ton so the coil runs colder and pulls out more moisture.

Every part of the indoor side has to handle that flow.

The matched coil. The 4-ton coil is rated as a pair with the condenser, and the pair is what the efficiency rating and the compressor warranty are based on. It also has to fit the furnace cabinet. A coil wider than the furnace needs a transition, and a 4-ton coil is often taller than the 3-ton it replaces, which can mean reworking the supply plenum. The evaporator coil guide covers what a mismatched coil costs you.

The furnace blower. The blower in the furnace moves the air for the cooling too. Many furnaces are built for a maximum cooling size, and a furnace that topped out at 3 or 3.5 tons cannot move 1,600 CFM. If it cannot, the coil runs too cold, can freeze, and the compressor pays for it. The furnace data plate or its literature states the limit. If it falls short, the honest quote is a full changeout at $6,500 to $22,000.

The ducts, and especially the return. Ducts sized for 1,200 CFM do not carry 1,600 quietly. Return air is the usual bottleneck: a single filter grille that was adequate for 3 tons is often too small for 4. The symptoms are whistling grilles, a filter sucked into its slot, and high static pressure that shortens blower life. Adding a return or enlarging a trunk runs $10 to $35 per linear foot.

The line set and the circuit. A 4-ton condenser usually wants a larger suction line than a 3-ton, and it draws more current. Check the minimum circuit amps and maximum breaker size on the new nameplate against the existing breaker and wire. Neither is a reason to avoid 4 tons, but both belong on the quote rather than in a change order.

A worked example: going from 3 to 4 tons after an addition

A 2,300 square foot house in a hot climate has had a 500 square foot family room added. The old 3-ton system cannot keep the new room cool, and a load calculation comes back at just under 4 tons. The furnace is five years old and rated for 4 tons of cooling, but the house has one return and the trunk stops short of the new room.

• 4-ton condenser and matched coil: $5,600 to $12,000
• New return and trunk extension: 40 linear feet × $10 to $35 per foot = $400 to $1,400
• Total: $6,000 to $13,400

The duct line, $400 to $1,400, is what makes the 4-ton unit work rather than whistle. A quote for the same condenser without it is cheaper and noisier, and the new room would still run warm. Had the furnace been rated only for 3 tons, the better answer would have been a full changeout instead, not a bigger condenser on a blower that cannot feed it.

Frequently asked questions

How much does a 4 ton AC unit cost installed?

$5,600 to $12,000, typically about $8,200, for the condenser and a matched coil on an existing furnace and ducts. Higher efficiency, a variable-speed compressor, or duct and electrical work push it toward the top.

How many square feet does a 4 ton AC cool?

Roughly 2,000 to 2,600 square feet in a typical climate, and more in a cool or tightly built house. Ceiling height, window area and duct location all move it, which is why a load calculation rather than a chart should pick the size.

Can I put a 4 ton condenser on ductwork built for 3 tons?

Sometimes, but rarely without changes. A 4-ton system needs about 1,600 CFM, and ducts and returns sized for 3 tons usually cannot carry it quietly. Ask the contractor to measure static pressure before quoting the larger unit.

Should I get a 3.5 ton or a 4 ton AC?

Whichever the load calculation supports. If the house calculates at about 3.6 tons, the 3.5-ton unit will dehumidify better and run longer, steadier cycles. Choose 4 only if the calculation, not the old nameplate, puts you there.

Related guides

• AC replacement cost — efficiency tiers and the extra lines on a cooling quote
• HVAC cost by house size — full systems priced from 2 to 5 tons
• Evaporator coil replacement cost — the matched coil on its own
• Compressor replacement cost — what a frozen coil and poor airflow eventually cost