How much does a new HVAC system cost?

The unit that drives price: tonnage (not square feet)

HVAC equipment is sized in tons of cooling, where one ton equals 12,000 BTU per hour. Square footage is only a rough proxy. A common rule of thumb is one ton per 400 to 600 square feet, which is what this tool uses to suggest a starting tonnage. But that rule is just a sanity check. Real sizing comes from a Manual J load calculation that weighs insulation, window area and orientation, ceiling height, air leakage, sun exposure, and climate. Two identical-sized homes can need different tonnage. Insist that any contractor run a load calc rather than just matching the size of your old unit, because the old unit may have been wrong too.

Why size matters for your wallet and your comfort: an oversized system short-cycles. It blasts cold air, hits the thermostat fast, and shuts off before it has pulled humidity out of the air. You get a cold, clammy house, more wear on the compressor, and a higher bill. An undersized system runs forever and never catches up on the hottest days. Bigger is not better, right-sized is.

The cost drivers this calculator weighs

Your range moves with each of these levers, which is exactly why two quotes can differ by thousands:

• Scope. An AC-condenser-only swap (reusing your furnace and coil) is the cheapest path. A full AC-plus-furnace split system costs more. A heat pump replaces both heating and cooling in one system. Ductless mini-splits are priced per zone, so a multi-zone home adds up fast.
• Efficiency tier (SEER2 and AFUE). SEER2 measures cooling efficiency and AFUE measures furnace efficiency. A base, builder-grade single-stage unit is the floor. Mid-tier two-stage and high-tier variable-speed equipment cost more upfront but use less energy and run quieter.
• Ductwork condition. Reusing sound ducts keeps cost down. Sealing leaky runs adds a little. Replacing or extending ductwork can add a large chunk, sometimes the single biggest surprise on a quote.
• Electrical and gas work. A like-for-like swap may need nothing. New circuits, a disconnect, a panel upgrade, or upsizing a gas line all add cost, and a fuel conversion adds the most.
• Climate and coastal exposure. Hot, humid regions run cooling loads harder, which nudges sizing and tier. Homes near salt water face faster condenser corrosion, so a coastal-rated or coated unit (and shorter lifespan) is worth budgeting for.

Repair or replace? A simple age-and-cost test

The hardest HVAC decision is whether to keep nursing an old system or replace it. Use three quick tests, then get a second opinion before any big-ticket repair:

• Age. AC and heat pumps typically last 12 to 15 years, furnaces 15 to 20. Past that window, the next failure is rarely the last, and you are pouring money into a system on its way out.
• The repair-cost ratio. A widely used guide: if a single repair costs more than about one third of the price of a new system, lean toward replacing, especially if it is the second major repair in a couple of years. Some people use the "5,000 rule" (age multiplied by repair cost; over 5,000 means replace).
• Refrigerant. Older systems use phased-out refrigerants. As supply tightens, a refrigerant leak on an aging unit gets expensive to recharge and the whole system often has to change anyway.

If the system is newer and only one part failed, repair is usually the smart money. If it is old, inefficient, on phased-out refrigerant, and failing again, replacement pays you back in lower bills and reliability. A new high-efficiency system also throws off a comfort and resale benefit that a patched old unit never will.

What a higher SEER2 actually buys you

Paying up for efficiency is a payback question, not a moral one. A higher SEER2 lowers the energy it takes to cool your home, but the savings only matter in proportion to how many hours you run the system and your electricity rate. In a hot climate that runs cooling most of the year, a jump from base to high tier can pay for itself in a reasonable number of years. In a mild climate where the AC runs a few months, the premium takes much longer to earn back. Variable-speed equipment also runs quieter and dehumidifies better, which is a real comfort win in humid areas even before the energy math. Run the numbers on your own utility bill before you pay for the top tier, and weigh any tax credits or utility rebates separately (verify the current IRS and utility figures, as of 2026-06-06).

Florida and Gulf Coast: humidity, cooling load, and salt air

In Florida and along the Gulf, cooling is the dominant load, so a few regional factors deserve weight in your budget. Humidity means dehumidification is half the job, which favors right-sized, variable-speed equipment over an oversized single-stage unit that short-cycles and leaves the air clammy. Year-round cooling hours make a higher SEER2 pay back faster than it would up north. And salt air near the coast corrodes condenser coils and cabinets, so budget for a coastal-rated or coated outdoor unit and a shorter replacement cycle. Permit rules and code minimums vary by county and city, so verify locally before you commit.

Pro tips

• Get three bids and compare scope line by line, not just the bottom-line price. The cheap bid often skips the load calc or reuses failing ductwork.
• Ask each contractor for the Manual J load calculation in writing. If they size by eyeballing the old unit, keep shopping.
• Match the indoor and outdoor units. A new condenser paired with an old, mismatched coil loses efficiency and can void the warranty.
• Ask what the quote excludes: permits, ductwork, electrical, thermostat, haul-away, and a new line set are common add-ons.
• Register the equipment after install to lock in the full manufacturer parts warranty, and ask separately about the labor warranty.
• Right-size, do not oversize. A correctly sized two-stage or variable system beats a bigger single-stage unit on comfort and bills.

Frequently asked questions