A full HVAC system replacement (AC + furnace or heat pump) costs $5,000–$12,500 in 2026. Heat pumps now win on operating cost in most climates — and federal incentives still apply.
Central AC replacement alone: $4,000–$8,000. Gas furnace: $3,500–$7,000. AC + furnace combo: $7,000–$12,500. Ducted heat pump (heating + cooling in one): $6,500–$13,000. Ductless mini-splits: $3,500–$5,500 per zone — often the best answer for additions and garages.
An oversized system short-cycles, wears out early, and dehumidifies poorly. Insist on a Manual J load calculation — not a rule-of-thumb 'ton per 500 sq ft'. Contractors who skip the load calc are guessing with your money.
Federal tax credits still cover up to 30% (capped at $2,000) for qualifying heat pumps, plus many state and utility rebates stack on top. Ask each bidder to itemize which SEER2/HSPF2 tiers qualify — the incentive often closes the gap between a mid and high-efficiency unit.
Leaky or undersized ducts waste 20–30% of system output. Duct sealing runs $500–$2,000, full replacement $2,500–$6,000. A good installer inspects ducts before quoting; a great one includes static-pressure readings in the proposal.
| Item | Low | High |
|---|---|---|
| Central AC (3-ton, installed) | $4,000 | $8,000 |
| Gas furnace (80–96% AFUE) | $3,500 | $7,000 |
| Ducted heat pump system | $6,500 | $13,000 |
| Ductless mini-split (per zone) | $3,500 | $5,500 |
| Duct sealing / repair | $500 | $2,000 |
| Smart thermostat (installed) | $200 | $500 |
A straight swap takes 1 day. Adding or replacing ductwork extends it to 2–4 days.
In most US climates a modern cold-climate heat pump costs less to run than gas. Below sustained 0°F, dual-fuel (heat pump + gas backup) is the usual answer.
14.3 SEER2 is the federal minimum; 15.2–17 is the value sweet spot. Above 18 only pays back in hot climates with long cooling seasons.
Rule of thumb: if the repair costs more than $5,000 minus ($100 × the unit's age in years), replace.
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