Replacing a 3-ton central AC costs $6,000 to $18,000 installed. A gas furnace alone runs $2,800 to $6,400. The complete AC-plus-furnace system most homes eventually need lands between $7,900 and $22,000, with typical jobs at $8,000 to $15,000. Here's how the number is built, how to sanity-check a quote, and when the efficiency upsell actually pays.
Equipment is 30 to 50% of an HVAC invoice. A 3-ton condenser plus coil wholesales for $1,700 to $5,000 depending on tier. Everything else on the quote is labor and site work: the crew, refrigerant line replacement, the condenser pad, electrical disconnects, duct modifications, permits, and the company's overhead and warranty reserve. Those costs swing by region, by company size, and by how busy the install calendar is.
The other reason for the spread is that "replacement" means different scopes. A drop-in changeout that reuses the existing pad, lines, and ductwork can't honestly be compared with a job that replaces the line set, reworks return drops, and adds zoning. When you collect bids, and you should collect three, make them compete on the same scope sheet.
Cooling capacity is measured in tons, one ton being 12,000 BTU per hour. The quick rule: 500 to 600 square feet per ton for typical existing homes, 600 to 800 for tight new construction. An 1,800 sq ft ranch at 600 square feet per ton needs a 3-ton unit.
The professional answer is a Manual J load calculation, which accounts for insulation, window area and orientation, air leakage, and climate. Bigger is not better: an oversized AC satisfies the thermostat in short bursts, and short cycles mean poor dehumidification, uneven rooms, and early compressor death. If a bidder sizes your system by reading the badge on the old unit, that's a signal about the rest of their work too.
| System | Installed Cost | Best For |
|---|---|---|
| Central AC only | $6,000–$18,000 (3-ton) | Healthy furnace, dead condenser |
| Gas furnace only | $2,800–$6,400 (80 kBTU) | AC under 10 yrs old, furnace cracked |
| Complete AC + furnace | $7,900–$22,000 | Whole system past 12–15 yrs |
| Air-source heat pump (ducted) | $7,800–$15,900 | Moderate climates; replacing both at once |
| Ductless mini-split | $6,600–$11,000 (3-zone) | No ducts, additions, room-by-room control |
Worked example: 1,800 sq ft at 600 square feet per ton sizes to exactly 3 tons. AC at the $3,500-per-ton midpoint is $10,500; an 80,000 BTU furnace at $55 per thousand BTU adds $4,400; bundled together with one crew and one permit, the 10% discount brings the job to $13,410, comfortably inside the national band of $7,920 to $21,960 for that configuration.
Since January 2023 the federal efficiency floor is 14.3 SEER2. Stepping up to a 17 SEER2 unit cuts cooling energy by 1 − 14.3 ÷ 17, about 15.9%. On $600 a year of cooling that's $95 saved annually. If the efficiency premium is $1,500, payback runs 16 years in a two-season climate and closer to 6 in Phoenix or Tampa, where the cooling meter spins ten months a year. The variable-speed furnace pitch follows the same shape: real comfort gains, especially with zoning, but the pure energy math rarely clears the premium alone.
Two yeses, or a yes plus refrigerant trouble, points to replacement. One more factor: if your system runs on R-22, phased out in 2020, a leak makes the repair-vs-replace question rhetorical, since recharge refrigerant sells by the pound at salvage-era prices.
Enter your square footage and system type; get the size your home needs, the national cost band, and the SEER2 upgrade savings.
HVAC Replacement Cost Calculator →First, replace in the shoulder seasons when install calendars are open and bids compete. Second, tighten the envelope before you size the equipment: air sealing and attic insulation (check our insulation calculator) can drop the tonnage you need, and a smaller system is a cheaper system in every tier. Third, ask about utility rebates rather than financing promotions; manufacturer-sponsored 0% offers are usually priced into the quote, while efficiency rebates are money your utility genuinely sends back.
A complete 3-ton AC plus gas furnace replacement runs $7,900 to $22,000 installed, with most jobs landing between $8,000 and $15,000. Bryant's 2026 pricing guide puts full-system replacement nationally at $5,000 to $28,000 depending on system type and efficiency. AC alone is $6,000 to $18,000 for 3 tons; a gas furnace alone is $2,800 to $6,400.
Usually yes if both are past 10 years. The coil and blower work as a matched set, so a new AC on a dying furnace loses efficiency and often the warranty. Doing both at once also saves roughly 10% versus two separate visits. If the furnace is under 8 years old and healthy, replacing the AC alone is defensible.
Check three things. Equipment should be itemized (a 3-ton condenser alone runs $1,700 to $5,000). The sizing should come from a Manual J load calculation, not the old unit's badge. And the quote should specify line-set replacement, a new pad, and proper commissioning with documented superheat and airflow numbers. Quotes lacking all three are guesses wearing letterhead.
Prices don't move by month as much as wait times do, but the dead of summer and the first cold snap of winter are when emergency replacements happen, and emergency buyers negotiate nothing. Booking in spring or fall gets you scheduling flexibility and room to collect competing bids. Off-season promotions in those shoulder months are also common.