Furnace Replacement Cost in 2026

AFUE, explained

AFUE (Annual Fuel Utilization Efficiency) is the percentage of fuel a furnace turns into usable heat. A 95% AFUE furnace wastes only 5% of its fuel; an 80% AFUE furnace wastes 20%, venting it out the flue. Higher AFUE costs more up front but lowers your winter bills: the payback depends on your climate and local gas prices, and runs faster in a cold climate where the furnace works harder and longer each year, like Minneapolis.

High-efficiency gas furnaces (generally 90%+ AFUE) condense water vapor out of the exhaust to recover extra heat, which means they vent through PVC pipe rather than a metal flue and produce condensate that needs a drain: a genuinely different installation, not just a better furnace in the same box. That's part of why the high-efficiency tier's price range runs so much wider than standard-efficiency: venting and condensate drainage sometimes require new piping runs that a straight swap doesn't.

Single-stage, two-stage, or modulating

Beyond AFUE, a furnace's "stage" describes how it ramps output rather than just how efficiently it burns fuel:

• Single-stage: full blast or off, nothing in between. The cheapest to buy, and the noisiest and least even-heating option, since the system cycles on at full output then shuts off rather than modulating.
• Two-stage: runs at a lower output most of the time, kicking up to full output only on the coldest days. Quieter, more even heat distribution, and better humidity control than single-stage, for a moderate price premium.
• Modulating: continuously adjusts output across a range (often 35-100%) rather than switching between two fixed stages. The most even heat and the quietest operation, and the most expensive tier, usually paired with the highest AFUE ratings, which is why modulating furnaces sit at the top of the high-efficiency price range above.

Signs it is time to replace

Age past 15 years, rising heating bills with no other explanation, uneven heating between rooms, frequent repairs, or a cracked heat exchanger (a genuine carbon-monoxide risk, not just a performance issue) all point toward replacement rather than another repair. A furnace that short-cycles, turning on and off repeatedly rather than running a full heating cycle, is often oversized for the home or failing, either of which a licensed technician should diagnose before you decide. If your AC is also aging, replacing both together in one visit saves on shared labor and ensures the two systems are actually matched for efficiency.

What drives installation cost beyond the furnace itself

The furnace unit itself is only part of the bill. Ductwork condition matters: a furnace sized correctly for the home but connected to leaky, undersized or poorly laid-out ducts won't perform to its rating, and duct repair or modification is a separate line item from the furnace swap. Venting changes (standard to high-efficiency, or vice versa) can require new PVC venting runs through walls or the roof. A gas line that needs upsizing for a larger furnace, or an electrical circuit that needs upgrading for a variable-speed blower motor, are both real but occasional add-ons a flat "furnace cost" figure doesn't capture: ask specifically whether your quote includes any of these before comparing it against another.