Short answer: Six things move a furnace replacement price more than anything else: the size the house actually needs, the efficiency tier you pick, whether the venting has to change, the condition of your ducts, the gas and electrical work required, and how hard the equipment is to get in and out. Everything else is rounding. If you understand those six, you can read any furnace quote in the valley and know what you are looking at.
We have been replacing furnaces in Walla Walla Valley homes since 1949. What follows is what we actually find when we open up a house, and why two bids on the same furnace can be far apart.
1. What size furnace does the house actually need?
Size is measured in BTUs, and it should come from a load calculation, not from reading the label on the old unit. The old unit may have been wrong for decades. Plenty of homes were fitted with whatever was on the truck that week.
A load calculation accounts for square footage, insulation levels, window area, ceiling height, and orientation. It changes the answer more than people expect. We have replaced units in older homes where the correct size was meaningfully smaller than what was there, because someone had added insulation and new windows in the years since.
An oversized furnace costs more and heats worse. It blasts, satisfies the thermostat, shuts down, and repeats. You feel that as hot and cold swings, and the constant starting and stopping is hard on the equipment. Undersized is its own problem in January, when the system runs continuously and still cannot catch up. Getting size right is free. It just takes someone doing the work.
2. How much does furnace efficiency change the price?
Furnace efficiency is stated as AFUE, a percentage of fuel converted to usable heat. There is a real dividing line between standard efficiency furnaces and high efficiency condensing furnaces, and it is not just the price of the box.
Condensing furnaces pull so much heat out of the exhaust that the exhaust comes out cool and wet. That changes what happens next, which brings us to the third item.
3. Does the venting have to change?
This is the cost driver homeowners almost never see coming. A standard efficiency furnace vents hot exhaust up a metal flue or masonry chimney. A high efficiency condensing furnace cannot use that chimney. It vents through PVC pipe out a sidewall, and it produces condensate that has to be drained.
So moving up to high efficiency can mean:
- New PVC intake and exhaust pipe routed to an exterior wall
- A condensate drain line, and sometimes a condensate pump
- Sealing or relining the old chimney if a water heater still shares it
That last one catches a lot of people. In older houses around Dayton and Waitsburg we frequently find a furnace and a water heater sharing one chimney. Pull the furnace out of that chimney and the water heater is left venting alone into a flue now too large for it, which is a safety problem that has to be corrected. It is real work, it belongs on the quote, and a bid that leaves it off is not cheaper. It is incomplete.
4. What condition are the ducts in?
Your furnace can only be as good as the ducts attached to it. We routinely find crushed runs in crawl spaces, joints that pulled apart years ago, and returns that are undersized for the airflow the new system needs.
Leaky ducts in an unconditioned crawl space or attic mean you are paying to heat the space under your floor. Undersized returns mean the new furnace runs hot, strains, and shortens its own life. Sealing, repairing, or resizing sections adds to the price. It also usually pays for itself in comfort and in equipment lifespan.
When you compare bids, ask each contractor what they found in the ducts. If one says nothing at all, that is information about the inspection, not about your ducts.
5. What gas and electrical work is required?
A new furnace may need a different gas line size than the old one, especially if you are changing capacity. It needs a properly sized electrical circuit and a service disconnect. Modern furnaces also have control boards and safety devices that older wiring sometimes does not support cleanly.
If you are switching fuel types entirely, that is a much larger conversation with its own line items. Either way, this work should be listed separately on the quote so you can see it rather than finding it buried in a single lump sum.
6. How hard is the equipment to get to?
Labor time is real cost. A furnace in a wide open garage with a roll up door is a different job than the same furnace in a low crawl space, a tight attic, or a closet that has to be partially disassembled to get the old unit out.
Removal and disposal of the old furnace counts here too. So does anything the crew has to protect or move on the way through the house. None of this is padding. It is hours, and hours are what installation labor is made of.
Are there rebates or tax credits on a new furnace?
Sometimes. High efficiency equipment is commonly eligible for federal energy efficiency tax credits, state efficiency programs, and utility rebates. Eligibility usually depends on the equipment hitting a minimum efficiency rating, which is one more reason the efficiency choice matters.
We are not listing amounts, because these programs change and printed numbers go stale. One local point worth knowing: because we serve homes on both sides of the state line, we see this constantly. A household in College Place and a household in Milton-Freewater are looking at different state programs entirely. Ask your contractor to confirm what is currently available for your specific address and utility, and to show you where it came from.
When should you repair instead of replace?
We would rather tell you to keep your furnace than sell you one you do not need. Cases where repair is usually the better call:
- The furnace is under about ten years old and has a single failed component
- The failed part is inexpensive and the rest of the system tests clean
- You are selling the house within a couple of years
- Nobody has actually diagnosed the problem yet, only guessed at it
The genuine replace signals are different: a cracked heat exchanger, a unit past its expected service life that is failing repeatedly, or repair costs that are climbing toward a meaningful share of a new system.
How do I read a furnace quote?
A complete quote names the exact model and its AFUE rating, states the calculated size and where that number came from, lists venting work separately, lists any duct and gas and electrical work separately, includes the permit and inspection, and states the labor warranty next to the manufacturer warranty. Compare those six lines across bids and the differences stop being mysterious.
We are NATE certified and a Daikin Comfort Pro, and we quote flat and in writing before any work starts. The price you approve is the price you pay.
Next step
If you have a furnace quote and want a second set of eyes on it, we will look at it for free, with no obligation and no pressure to buy from us. Call (509) 525-8073 and bring your questions.