How to work out what to price
Start with the label on your old system. The model number usually hides the size: a number like 36 in it often means 36,000 BTU, which is 3 tons. That tells you what you have now, though perhaps not what you need. An old system may be oversized, and a house that has gained insulation or new windows may need less.
Only a load calculation really answers that. ACCA's Manual J looks at your walls, windows, insulation and climate. A common rule of thumb says 400 to 600 square feet per ton, but ACCA's blog reports that 40 real calculations averaged 1,431. We show the old rule as a rough range because people ask for one, and we flag it, since it can oversize a system by two or three times. Ask each contractor for a Manual J in writing.
Then look at the ducts. Get them tested if you can, since it is the biggest swing in the price. A system with leaky or undersized ducts will underperform whatever you buy. If the ducts are fine, reusing them saves a large sum.
A worked example
Here is a 3 ton heat pump with new ductwork, at the baseline region. These lines come from the same formula the calculator above runs.
3 ton heat pump, new ducts
- Heat pump: $5,500 to $15,000, average $9,000
- New ducts: 3 × $2,000 to $3,000 = $6,000 to $9,000
- Total: $11,500 to $24,000
The federal credit will not help you here. The IRS says the 25C tax credit is not allowed for property placed in service after December 31, 2025. To see whether a heat pump would pay back, compare the running costs with the heat pump savings calculator, and the heating cost calculator for your current fuel.
Installed cost by system
These are PICKHVAC's figures at the baseline region. EIA's cost table is a useful floor: it lists a typical 3 ton heat pump at $6,880 and a 3 ton central AC at $5,320 in its older 2022 dollars, and its figures do not itemize ductwork.
| System | Low | Average | High | With new ducts, high |
|---|---|---|---|---|
| Heat pump | $5,500 | $9,000 | $15,000 | $24,000 |
| Furnace and AC | $6,500 | $10,500 | $18,000 | $27,000 |
| Ductless, 3 zones | $5,400 | $10,500 | $19,500 | No ducts |
Mistakes that cost you on a new system
- Sizing by square feet. It is quick, but it often oversizes. A large system costs more, and it can cycle on and off.
- Unlike quotes. One may include new ducts and a thermostat, and another may not. Get the same scope from each.
- Counting on a credit that ended. The federal credit ended for property placed in service after December 31, 2025. Ask about utility rebates, which we did not research.
- A conversion price as a typical one. Cost vs. Value's $19,484 is for a five-head ductless job, not a like-for-like swap.
- Forgetting the panel. Moving from gas to electric may mean electrical work, which is not in this range.
Questions
How much does it cost to replace an HVAC system?
About $6,500 to $18,000 for a 3 ton furnace and AC, and about $5,500 to $15,000 for a 3 ton heat pump, on PICKHVAC's figures. This Old House's homeowner survey puts a full replacement at about $8,209 on average. New ducts can add as much again.
What does a new AC unit cost for a 2,000 sq ft house?
Floor area alone cannot say, because the size depends on your house's heat load. PICKHVAC gives $5,500 to $12,000 for 2.5 to 3.5 tons. A proper Manual J calculation sets the size, and it may be smaller than an old rule of thumb suggests.
What size system does my house need?
One sized by a Manual J load calculation, not by floor area. The rule of 400 to 600 square feet per ton is common, but ACCA's blog reports 40 real calculations averaging 1,431 square feet per ton. A system that is too big can cost more and work worse.
Is there a federal tax credit for a new HVAC system?
No, not for new installs. The IRS says the Section 25C credit is not allowed for property placed in service after December 31, 2025. State or utility rebates are separate, and we did not research them, so ask your utility and your contractor.
Do I need new ductwork?
Only if the old ducts are leaky, undersized or damaged, so ask for them to be tested. New ducts run $2,000 to $3,000 per ton on HVAC.com's figures, which is close to the price of the equipment. It is worth knowing before you compare quotes.
Should I wait for my system to fail?
Waiting saves money until the day it fails, when you may have to take what is available fast. Getting quotes while it still runs lets you compare. A contractor's advice on repair or replacement depends on your system's age and condition.
This HVAC replacement cost is a planning range from contractor-site estimates, and quotes vary with region, brand and access. Electrical upgrades, permits, disposal and asbestos surprises are not counted. The rough size is no substitute for a Manual J load calculation. Only a written quote from a licensed HVAC contractor is binding.
Sources and review
- HVAC system cost, PICKHVAC, 2026.
- Updated buildings sector appliance and equipment costs, appendix A, U.S. Energy Information Administration, 2023.
- How much does ductwork cost?, HVAC.com, 2024.
- Manual J load calculations vs. rules of thumb, ACCA, 2016.
- Energy efficient home improvement credit, Internal Revenue Service, 2026.
- HVAC replacement cost calculator, This Old House, no date shown, read November 2026.
Checked in November 2026. Spotted a wrong number? Report it and it goes in the corrections log.
How this is calculated
Every figure below is read from the code that produces the answer, so what is written here is what the calculator ran. The constants were last checked against their sources in November 2026.
The arithmetic
Central system
Cost = Price at 3 tons × Tons ÷ 3 × Region
- Price at 3 tons
- A low, an average and a high from a contractor site
Worked through: 9000 × 3 ÷ 3 × 1 = 9000
New ducts
Ducts = Tons × Cost per ton
- Cost per ton
- $2,000 to $3,000
Worked through: 3 × 2000 = 6000
The constants, and where they come from
INSTALLED_COST
Modelled from published dataInstalled cost, low, average and high, by system
- heatPump
- 5500, 9000, 15000
- furnaceAc
- 6500, 10500, 18000
- ductless
- 1800, 3500, 6500
Applies to: United States, a contractor site's figures. Central systems at 3 tons, and ductless per zone
Source: HVAC system cost, PICKHVAC, published 2026-05, read 2026-11.
EIA's government figures are lower but older, and they do not itemize ducts, so they are shown as a floor on the page. No inflator specific to HVAC was found.
BASE_TONS
Modelled from published dataThe size the central figures are written for, in tons
Applies to: Scaling a central system by size
Source: HVAC system cost, PICKHVAC, published 2026-05, read 2026-11.
Scaling in a straight line with tons is our own model. It fits PICKHVAC's table by size fairly well, at 1.5 to 2 tons and at 4 to 5 tons.
DUCT_COST_PER_TON
Modelled from published dataNew ductwork per ton, low and high
- 0
- 2000
- 1
- 3000
Applies to: United States, a contractor site's figures
Source: How much does ductwork cost?, HVAC.com, published 2024-12, read 2026-11. This source is about 2 years old, and it is the one the figure rests on.
HVAC.com prints $6,000 to $9,000 for 3 tons and $8,000 to $12,000 for 4 tons. New ducts can come close to the price of the equipment.
SQ_FT_PER_TON
Published range, narrowedA contractor's rule for square feet per ton, used only for a rough range
- 0
- 400
- 1
- 600
Applies to: A first guess only, and it is not a sizing method
Source: Manual J load calculations vs. rules of thumb, ACCA, published 2016-10, read 2026-11. This source is about 10 years old, and it is the one the figure rests on.
ACCA's blog gives this rule to argue against it, with 40 Manual J calculations averaging 1,431 square feet per ton. Many homes would be oversized by the rule, so it is flagged wherever it appears.
PROJECT_MULTIPLIER
ModelledMultiplier by United States region, applied to this page's modelled rates
- northeast
- 1.1
- southeast
- 0.94
- midwest
- 0.97
- southwest
- 1
- west
- 1.13
Applies to: United States, five broad regions
No published figure exists for this. It is derived, and the derivation is below rather than a citation to something that does not say it. Last checked in November 2026.
The site's own model, shared across cost calculators. No published series was found. PICKHVAC says coastal and urban areas run well above the Midwest.
What the labels mean
- Modelled from published data:
- derived rather than measured, calibrated against the source named beside it.
- Published range, narrowed:
- a source publishes a range and this calculator uses a representative value from it.
- Modelled:
- derived rather than measured, and the derivation is shown.
If a figure here looks wrong, it may be. Tell us what you found and we will check it against the source and publish a correction if it needs one. How constants are chosen and how often they are reviewed is set out in our methodology.
How to use the HVAC replacement cost calculator
- 1
Read your old system's label for its size in tons
- 2
Choose the kind of system you want
- 3
Say if the ducts have to go
- 4
Set your region
- 5
Use the range to check written quotes, and ask for a Manual J calculation
What this calculator assumes
Every estimate here rests on the assumptions below. Where your job differs from one of them, the figure will differ too.
- Central system prices are stated at 3 tons and scaled in a straight line by size, which is our model
- New ducts are priced by the ton from a contractor site, and they can come close to the price of the equipment
- It leaves out electrical upgrades, permits and any gas line work
- The rough tons range uses a contractor's rule that often oversizes a house, so it is only a first guess
Pro tips
- Ask each contractor for a written Manual J, and see what they used
- Get at least three written quotes with the same scope
- Ask about electrical work if you are switching from gas to a heat pump