What a furnace replacement costs
This Old House puts the whole job at $2,825 to $6,846, citing HomeAdvisor. NerdWallet puts it at about $2,823 to $6,888, citing 2026 data from Angi, which owns HomeAdvisor.
This Old House says to count more than the furnace: the labor, hauling off the old unit, permits and any changes to your heating system. Ask for all of that in one price.
The fuel changes the price. This Old House says an electric furnace costs the least to put in and the most to run. For a propane furnace they don't agree: This Old House says $3,000 to $6,000, and NerdWallet says $3,700 to $14,200.
Home heat around here
The Census Bureau estimates about 5,000 occupied homes in Boundary County. About 39% heat mainly with utility gas, 29% with wood, 25% with electricity and 4% with propane or other tank gas.
Source: U.S. Census Bureau, House Heating Fuel (B25040), Boundary County. Heating fuel counts checked in the 2020 to 2024 survey estimates, Oct 28, 2026.
That mix matters when a furnace gets replaced, because the fuel decides who else is part of the job.
Avista's natural gas tariff, filed with the Idaho Public Utilities Commission, names Bonners Ferry in its gas service area. No other Boundary County town is on that list.
Source: Avista Utilities natural gas tariff, Idaho Public Utilities Commission. Towns in the gas service area checked on the tariff's rate area sheet, Oct 28, 2026.
A propane furnace runs off a tank instead, so the local propane businesses come into it.
DOPL's inspector list sets the same HVAC inspection days for Bonners Ferry, Moyie Springs, Naples, Porthill, Eastport and Copeland: Monday, Wednesday and Friday.
Source: Idaho DOPL, Inspector List with Schedules. HVAC inspection days checked on DOPL's August 2026 inspector list, Oct 28, 2026.
When it's time for a new one
There's no set age. ENERGY STAR, the federal energy efficiency program, gives a few signs to watch for.
ENERGY STAR also says a furnace with its label is 15% more efficient than a conventional one. If the old furnace still runs, you have time to get more than one quote and pick the day.
Permits and install day
NerdWallet says a standard furnace install can take four to eight hours. Ask how long the heat will be off, and who will be there for the state inspection.
The inspection needs the permit number, so it helps to know early whose name the permit is in. DOPL says: "A homeowner may purchase a permit only when they are doing electrical, plumbing, or HVAC work on their primary and secondary residence and related outbuildings."
Source: Idaho DOPL, HVAC Frequently Asked Questions. Homeowner permit rule checked on DOPL's HVAC questions page, Oct 28, 2026.
Who handles each part
- The furnace: a licensed HVAC contractor. See the local heating businesses, and look up any license on DOPL's public license search.
- Natural gas service in Bonners Ferry: Avista Utilities, the gas company on that tariff.
- A propane tank: the local propane businesses.
- Sizing: our heating BTU calculator works out the heat a room, garage or shop loses on a cold night. For the whole house, ask the contractor to show how they sized the new furnace.
Air duct cleaning cost
NerdWallet notes that older ductwork may not be compatible with a new furnace.
National guides put air duct cleaning at about $250 to $1,000. This Old House says $450 to $1,000, citing the National Air Duct Cleaners Association, and NerdWallet says $270 to $500.
EPA's page lists when a cleaning may make sense and what a proper job includes. Give it a read before you book one.
Ask before you hire
Five questions for anyone quoting a new furnace. Tick them off as you go.
Sources
| Source | What was checked | Last checked |
|---|---|---|
| This Old House, furnace cost guide (updated May 25, 2026) | Furnace replacement range and its HomeAdvisor credit, what to count, and electric and propane notes checked | Oct 28, 2026 |
| NerdWallet, furnace cost guide (updated March 30, 2026) | Furnace replacement range and its Angi credit, propane price, install time and ductwork note checked | Oct 28, 2026 |
| U.S. Census Bureau, House Heating Fuel (B25040), Boundary County | Heating fuel counts checked in the 2020 to 2024 survey estimates | Oct 28, 2026 |
| Avista Utilities natural gas tariff, Idaho Public Utilities Commission | Towns in the gas service area checked on the tariff's rate area sheet | Oct 28, 2026 |
| Avista Utilities | Natural gas service checked on Avista's home page | Oct 28, 2026 |
| Idaho DOPL, HVAC Frequently Asked Questions | Permit rules and inspection notes checked on DOPL's HVAC questions page | Oct 28, 2026 |
| Idaho DOPL, Inspector List with Schedules | HVAC inspection days checked on DOPL's August 2026 inspector list | Oct 28, 2026 |
| Idaho DOPL, HVAC | Public license search link checked on DOPL's HVAC page | Oct 28, 2026 |
| ENERGY STAR, When is it time to replace? | Signs and the efficiency figure checked on ENERGY STAR's page | Oct 28, 2026 |
| This Old House, duct cleaning price guide (updated April 9, 2026) | Duct cleaning range and its credit checked | Oct 28, 2026 |
| NerdWallet, duct cleaning price guide (updated April 22, 2026) | Duct cleaning range checked | Oct 28, 2026 |
| U.S. EPA, Should You Have the Air Ducts in Your Home Cleaned? | Routine cleaning statement checked on EPA's duct cleaning page | Oct 28, 2026 |