The two figures that agree
| Source | Central AC range | Average |
|---|---|---|
| Fixr, August 2025 | $5,800 to $14,400 | $8,750 |
| This Old House, October 2026 | $6,345 to $10,575 | $8,460 |
$290 apart, our subtraction, from two publishers fourteen months apart. That is the number to budget against for a central system in an average house.
Fixr's range is explicitly a square footage calculation: they price central air at $2.90 to $7.20 per square foot, and 2,000 square feet times those rates is $5,800 to $14,400, which is their headline exactly. They say plainly why 2,000 square feet is the benchmark: most homes use a unit that fits that size.
Their table by house size:
| Home size | Installed |
|---|---|
| 800 sq ft | $2,320 to $5,760 |
| 1,000 sq ft | $2,900 to $7,200 |
| 1,200 sq ft | $3,480 to $8,640 |
The low end assumes you already have ducts and are only adding the unit. The high end assumes ducts have to be added or upgraded, which is the single biggest swing on this project.
The figure that does not agree, on the same page
This Old House opens its air conditioner guide like this: air conditioners cost an average of $16,759 for a full system installation, with prices ranging from $450 for window units to $10,575 for heat pumps.
Three things about that sentence are worth noticing, and we are going to be specific rather than vague:
- $16,759 is nearly double the $8,460 their own page gives for central AC, a gap of $8,299 by our subtraction.
- The stated range tops out at $10,575, which is below the average the same sentence announces. An average cannot sit above the top of its own range.
- $10,575 is labelled as a heat pump price in that sentence, but on the same page it is the high end of the central AC figures. Our heat pump page puts This Old House's own heat pump average at $8,042, not $10,575.
We are not going to pretend to know which of their numbers is the intended one. What we can tell you is that the figure a reader meets first on that page is not supported by the rest of it, and that the figure which is supported, $8,460, lands within $290 of an independent publisher.
Size, and the jump nobody explains
This Old House prices by tonnage, which is how AC capacity is actually sold:
| Tonnage | Average | Range |
|---|---|---|
| 1.5 tons | $8,448 | $4,853 to $18,657 |
| 2 tons | $8,551 | $4,940 to $18,854 |
| 2.5 tons | $8,586 | $4,940 to $19,051 |
| 3 tons | $8,654 | $5,026 to $19,051 |
| 3.5 tons | $8,723 | $5,026 to $19,249 |
| 4 tons | $13,136 | $5,762 to $37,017 |
| 5 tons | $16,312 | $5,892 to $39,286 |
Our reading, marked as ours. From 1.5 to 3.5 tons the average barely moves: $275 across more than double the capacity. Then 4 tons costs $4,413 more than 3.5 tons, and 5 tons another $3,176 on top. The step is at 4 tons, not spread across the range.
That shape is worth knowing before you let anyone round your sizing up. Going from 3 tons to 3.5 costs about $69 on these figures. Going from 3.5 to 4 costs thousands.
This Old House's own warning supports treating sizing carefully: too small and the unit works harder, raising bills and wear; too large and you spend more on energy you do not need.
A note on who is telling you this
This Old House's air conditioner page carries an advertiser disclosure stating that submitting your details connects you with partners of All Star Pros, who may contact you. The cost widget on that page sits directly above a quote form.
That does not make the figures wrong, and we use them on this page. It is context a reader is entitled to have, and we flag it wherever we meet it.
What moves your own number
- Ductwork. The difference between Fixr's low and high end is largely whether ducts already exist and are usable.
- Efficiency rating. Fixr notes that very hot climates require higher efficiency, which raises the unit price before any labor. Our SEER rating page prints both rating scales side by side and the regional minimums.
- Tonnage. See the step at 4 tons above.
- Whether the ducts are being cleaned or replaced. Cleaning is its own job at $300 to $800, on our air duct cleaning page.
- Whether you need heating too. A heat pump does both from one machine; our heat pump page prices that alternative, and our furnace page prices the heating half separately.
Buying heating at the same time is usually cheaper than buying it later, and our whole system page prices the pair. If the system you have is working but faulty, start with our AC repair page, where three publishers agree on the average within six dollars. Before you accept a tonnage, our sizing page shows how far the usual rule of thumb drifts, and our mini split vs central air page prices the ductless alternative against this one. Before you upsize the machine, our attic fan page covers the cheaper way to take heat out of the roof space it is fighting. And if the system you are replacing still runs R-22, our Freon page explains why the decision is usually already made.
Sources
- Fixr, Cost to Install Central Air, updated August 29, 2025 (the $5,800 to $14,400 range, average $8,750, per-square-foot figures and the table by home size)
- This Old House, How Much Does a Heat Pump Cost? (2026 Pricing), updated October 14, 2026 (their heat pump average of $8,042)
- This Old House, How Much Does an Air Conditioner Cost? (2026 Prices), updated October 2, 2026 (the $6,345 to $10,575 central AC figures, the $16,759 headline, the tonnage table, the advertiser disclosure)
Price figures are national US ranges from the sources above as of the date shown. Your local price depends on labor rates, permits and site conditions. Read how we get our numbers.