Furnace & AC Replacement Cost Calculator

Replacing both a furnace and central AC as a complete system averages $8,000 to $14,000 installed, with most homeowners paying around $10,000 to $12,000 for a mid-efficiency system in an average-size home. Furnace-only replacement runs $4,000 to $7,000 and AC-only $5,000 to $8,000. Costs scale with home size (larger homes need higher-tonnage equipment), efficiency tier (high-efficiency and variable-speed units cost significantly more), and whether ductwork needs modification or replacement. Replacing both units at once is usually more economical than doing them separately, since you share labor, equipment, and permitting. Enter your home size, system type, efficiency, and ductwork in the calculator above for a localized estimate.

Often yes, especially if both units are aging (10–15+ years). Replacing together means matched components that run more efficiently as a designed system, one project that shares labor and trip costs, a single warranty period, and no mismatch problems — modern AC refrigerants (R-454B/R-32) may not pair well with an old coil. If one unit is much newer or still under warranty, replacing only the failed unit can make sense. The key catch: if you replace just the AC, the new indoor coil must be compatible with your existing furnace's blower for proper airflow and efficiency, and vice versa. The calculator lets you price furnace-only, AC-only, the full system, or a heat pump so you can compare.

They're the efficiency ratings for cooling and heating. SEER2 (Seasonal Energy Efficiency Ratio 2) measures air conditioner and heat pump cooling efficiency — higher is better, ranging from about 14 (standard) to 20+ (premium); the 2023 update from SEER to SEER2 uses more realistic testing. AFUE (Annual Fuel Utilization Efficiency) measures gas furnace efficiency as a percentage — an 80% AFUE furnace turns 80% of the fuel into heat, while 90–98% AFUE 'condensing' furnaces are far more efficient. Higher ratings cost more upfront but cut energy bills; the payback depends on your climate, energy prices, and how long you'll stay in the home. The calculator's standard, high-efficiency, and premium tiers reflect these rating bands.

System size — 'tons' for cooling, BTUs for heating — is based on your home's heat load, not just square footage. A common rule of thumb is one ton of cooling per 500–600 sq ft, so a 2,000 sq ft home usually needs 3 to 3.5 tons. But proper sizing also depends on climate, insulation, window area and orientation, ceiling height, and air leakage. Oversized systems short-cycle — turning on and off rapidly, wasting energy and failing to dehumidify — while undersized systems run constantly and can't keep up. A professional should run a Manual J load calculation for an accurate size; square footage alone is just a starting estimate, which is what the calculator uses to gauge tonnage and cost.

It depends on your climate and energy prices. A heat pump both heats and cools using electricity (no gas), and modern cold-climate models work efficiently even in freezing temperatures. Advantages: very high efficiency (especially versus electric resistance heat), one system for year-round comfort, no combustion or carbon-monoxide risk, and eligibility for significant federal tax credits and rebates. A traditional gas furnace and AC can be cheaper to operate where natural gas is inexpensive and winters are severe. Many homes use a 'dual-fuel' setup — a heat pump with a gas furnace backup — for the best of both. Heat pumps are increasingly favored for efficiency and electrification incentives; the calculator prices a heat-pump system alongside the gas options.

Often, yes, and they can offset much of the premium for efficient equipment. Federal incentives include the Energy Efficient Home Improvement Credit (25C), offering tax credits up to $600 for qualifying AC or furnace units and up to $2,000 for qualifying heat pumps, plus income-based rebate programs that can cover a substantial portion of heat pump costs for eligible households. Many states, utilities, and manufacturers add their own rebates on top. Because these programs and their qualification tiers change, confirm current eligibility with your installer and a tax professional before counting on them. The calculator estimates the gross installed cost; subtract any credits and rebates you qualify for to get your net.

Yes, sometimes a lot. If your existing ducts are in good shape — properly sized, sealed, and not badly leaking — the new system connects to them at no extra cost. Minor modifications to the plenum or a few runs add about $800. But aged, undersized, or leaky ductwork that needs full replacement adds around $3,500, since it's a significant labor job of removing and re-running duct throughout the home. Bad ductwork undermines even the best equipment — leaks and poor sizing waste efficiency and cause uneven temperatures — so it's worth having the contractor evaluate the ducts during a replacement rather than bolting new equipment onto a failing distribution system.

Lean toward replacement when the AC is 12–15+ years old or the furnace 15–20+ and nearing end of life; when a repair costs approach half of a replacement (the '$5,000 rule' — multiply the repair cost by the unit's age, and if it tops $5,000, replace); when the AC uses phased-out, expensive R-22 refrigerant; when energy bills keep rising despite normal use; when the system needs frequent repairs or can't keep up on extreme days; or when rooms are unevenly heated and cooled. A new high-efficiency system can cut energy use 20–40% versus an old one, which helps offset the replacement cost over time. If the unit is newer and the repair is small, fixing it is usually the better call.

A complete quote should cover the equipment (furnace, AC condenser, evaporator coil, or heat pump), removal and disposal of the old equipment, installation labor, a new refrigerant line set or flush for AC work, electrical and gas connections, condensate drainage, sometimes a thermostat, permits and inspection, and startup and commissioning. Items often quoted separately include ductwork modification or replacement, electrical panel upgrades, gas line changes, a new pad or rooftop curb, zoning, air purification, and extended labor warranties. Get itemized quotes from at least three licensed HVAC contractors, confirm the equipment brand, model, and efficiency ratings, and verify the warranty terms for both parts and labor. Matching apples to apples across bids is what reveals the real value.

A straightforward furnace and AC replacement using existing ductwork typically takes 1 to 2 days, and a single furnace or AC swap can often be done in a day. It runs longer — 3 to 5 days — if ductwork needs modification or replacement, if the equipment is in a hard-to-reach spot like a cramped attic or crawl space, or if electrical or gas-line upgrades are required. The crew removes the old equipment, sets the new furnace and/or condenser and coil, connects refrigerant lines, electrical, and gas, adjusts ducts and plenum as needed, then tests and commissions the system. Most homes are without heating or cooling only during the working hours of the changeover, so it's rarely more than a day's disruption on a simple swap.