Furnace replacement cost is driven by five things: capacity, efficiency tier, venting requirements, ductwork condition, and access. We quote after looking, because the same furnace can carry very different installation costs in two houses on the same street.

What Sets the Price

Capacity. Larger homes need higher-output equipment. But bigger is not automatically better — an oversized furnace short-cycles, heats unevenly, and wears out ignition components faster. Correct sizing comes from a load calculation, not from matching what is there.

Efficiency tier. The spread between a standard-efficiency furnace and a high-efficiency condensing model is significant, and the venting changes that come with it add more.

Venting. Standard furnaces vent through metal flue. Condensing furnaces require PVC venting and a condensate drain. Moving between tiers means new venting, not a reused flue.

Ductwork. Undersized returns or leaking supply ducts limit what any furnace can deliver, and corrections add cost.

Access. An attic or tight closet installation takes substantially more labor than a garage with clear access.

The Costs Cheap Bids Leave Out

When you compare quotes, the difference is usually not the equipment. It is what each contractor included.

The orphaned water heater. If your old furnace shared a flue with a gas water heater and the new one vents separately, the water heater is left on a flue now oversized for it — a backdrafting risk that has to be corrected. This is a common finding and a common omission.

Gas line capacity. If the new unit demands more gas than the existing line delivers, gas line work is part of the job.

Permits. Required, and worth having — they protect you at resale, support insurance claims, and are a condition of many manufacturer warranties.

Commissioning. Measuring gas pressure, analysing combustion, and verifying temperature rise. It is invisible on day one and it is what determines whether the furnace performs for a decade.

A bid that is dramatically lower than the others is usually lower because one of these is missing.

The Efficiency Question in This Climate

Here is where we differ from the standard pitch.

Fredericksburg winters are short and mild. Furnaces here accumulate far fewer runtime hours than in cold climates, which is why they routinely outlast their national average lifespan — and also why there are fewer heating hours over which to recover an efficiency premium.

The payback on a top-tier condensing furnace is genuinely longer here than the brochures suggest, especially once venting changes are priced in. For many homes a good mid-tier furnace is the better value, with the difference spent on duct sealing or insulation, which deliver more comfort per dollar in this climate.

We will show you the numbers rather than steering you toward the larger invoice.

Worth Pricing Alongside

Given our long cooling season, replacement is the natural moment to price a heat pump as well. It handles both heating and cooling with one system, and in this climate it spends most of the heating season in its efficient range.

A hybrid fuel system pairs a heat pump with a gas furnace and switches automatically — often the best fit for homes that already have gas service.

Repair or Replace

Before pricing a replacement, it is worth confirming you need one.

A useful test: multiply the repair cost by the furnace’s age. If the result exceeds replacement, replacing is usually right. A cracked heat exchanger ends the discussion regardless — it allows carbon monoxide into your air.

We quote both repair and replacement so you can see the numbers side by side.

Getting a Real Number

Estimates are free and itemized — equipment, labor, venting, permits, and any corrections, listed separately so you can see what is required versus optional.

Financing is available. We serve Fredericksburg, Kerrville, Boerne, Comfort, and the surrounding Hill Country.

Contact 72 Degrees or call (830) 240-1835.