Open 24/7 for emergencies
A new gas or propane furnace in Great Falls runs $4,285 to $14,040 installed, keeping the AC you have. Half the houses here date from the 1970s and 80s.
Price range
$4,285-$14,040
8yrs @ 7.99%
$61/mo
15yrs @ 9.99%
$46/mo
Monthly figures on the starting price, the whole price financed, on approved credit. The lender sets the final terms. How financing works
Get your price in writing
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5.0 stars across 1,132 reviews
Two of our heating technicians beside a gas furnace, the cooling coil on top of it and the water heater to the right.
Licensed and insuredVirginia Class A contractor #2705192276
24/7 emergency serviceOften same-day, and we will tell you honestly when we can get there.
Our own HVAC installersA dedicated heating and cooling team, separate from our plumbers
Price in writing firstYou see every option priced before anything is ordered
What it costs
The same price book our estimator runs on, for a gas furnace on its own, 2 to 5 tons, keeping the air conditioner you have. A single-stage furnace in a small house sits near the bottom; a modulating one in a big house, near the top.
A gas furnace alone, keeping your air conditioner, installed
$4,285 to $14,040
or $71/mo at 0% APR for 60 months
A furnace and air conditioner together, installed
$8,898 to $23,000
or $148/mo at 0% APR for 60 months
Repair diagnostic visit, if it may be worth fixing
$99
Monthly figures: 60mo @ 0% APR on each starting price, the whole price financed, on approved credit. Longer plans lower the payment and cost more in total. The lender sets the final terms. How financing works
The HVAC replacement cost estimator narrows it to your house. Then a tech measures, and you get the installed price in writing, at no charge, before anything is ordered.
Natural gas or propane, in a house, a townhouse or a condo, we replace them all. Oil furnaces we don’t.
What’s different in Great Falls
Natural gas heats a smaller share of Great Falls than of Fairfax County: about 46 in 100 owner homes here, against 61 countywide. Propane fills much of the gap. About one owner home in twelve heats with propane from a tank in the yard, more than five times the county’s share. Both fuels burn in the same furnace; for a propane house it gets new burner orifices and a gas valve set for propane pressure before it’s lit.
The county’s tax records put the typical house in 22066 at 1985, and half went up in the 1970s and 80s. With fifteen to twenty years the usual run for a gas furnace, the one in a house that age is probably its second or third, and if the last swap came before 2011, it’s due again. The builder’s own furnace is likeliest in the 2000s houses, about one in nine here, and those have now seen seventeen to twenty-six winters.
What makes this a furnace-only job is a cooling side worth keeping. If the outdoor unit and the coil above the furnace are under ten years old or so and cool well, leave them. We read both model plates before pricing, so the new furnace’s blower delivers the airflow that air conditioner was built around. An outdoor unit labeled R-22 dates from before about 2010; then the pair, $8,898 to $23,000, is the price to see.
Three in four houses here are two stories, and the bedrooms often have their own furnace up in the attic. That swap takes more planning. The new furnace has to come through the hatch or the pull-down stair, it sits in a pan with a float switch so a blocked drain shuts it off before water reaches the ceiling, and a high-efficiency model’s condensate line has to be kept from freezing. The basement one is simpler: by the county’s books two in three houses here have a daylight basement, open at ground level on one side, so the old furnace can often go out a door instead of up the stairs.
By the numbers
From the Census Bureau’s 2020 to 2024 survey, owner-occupied homes unless it says otherwise.
When it’s time
With two furnaces, one quitting leaves the rest of the house heated, which buys time to decide calmly. If the cold floor’s furnace is past fifteen, let the $99 diagnostic visit price the repair, and set that beside the range for a new one.
It’s the wall that keeps the burner’s exhaust out of the air the furnace blows through the house. Nobody patches one; a crack ends the repair conversation.
Fifteen to twenty years is a gas furnace’s usual run. Past that, parts get harder to find and each repair buys less time.
Permits, locally
Fairfax County requires a permit to replace any gas appliance, even like for like: a gas water heater, furnace or boiler. Replacing a fuel-burning appliance also needs a chimney vent certification. Source.
Our Virginia Class A contractor license, 2705192276, is on the side of the van.
Choosing who installs it
Questions to ask anybody who quotes you, us included.
The hatch size, the walkway, the drain pan and where the condensate ends up all change an attic job. A price for the upstairs furnace written from the basement is a guess about the hardest part.
Ask how they picked the size. Copying the old nameplate repeats whatever was guessed when the house was built.
A new furnace has to work with the coil and the outdoor unit already there. Ask whether they looked at both before quoting a furnace on its own.
A good company puts the repair price next to the replacement range and lets you choose. Already holding somebody’s big number? Take the free second opinion first.
Two of our crew going over a work order before the day's calls.
From our Google reviews
5.0 stars across 1,132 reviews. Read them on our reviews page.
Moises and Oscar did a superlative job doing a custom installation of a new HVAC unit in a tight basement space. And they then took the time to go over system operation. Top tier job and service in all respects!
Questions
It’s priced on the same range as natural gas, $4,285 to $14,040 installed. The furnace is converted for propane before its first light, and your propane company, which usually owns the tank, is the one to call about the tank and the line up to the house.
$4,285 to $14,040 installed for a gas furnace on its own, keeping the air conditioner you have; size and efficiency set where yours lands. A furnace and air conditioner together run $8,898 to $23,000. The HVAC replacement cost estimator gives your house its own number.
Fix the small parts on almost any furnace. Past fifteen years, with a repair over a third of the price of a new one, replacing usually wins. Not sure which you’re looking at? The diagnostic visit is $99, and the tech prices the repair before starting it.
Ready when you are
Call, or send the form at the top. A tech measures the house and puts the installed price in writing before anything is ordered, and if the old furnace is worth fixing, you’ll hear that first.
SwiftPro Heating, Cooling & Plumbing
4230 Lafayette Center Dr N, Chantilly, VA 20151
44679 Endicott Dr, Suite 211, Ashburn, VA 20147
Virginia Class A contractor license #2705192276
SwiftPro Heating, Cooling & Plumbing is a licensed, BBB Accredited (A rating), independently owned heating, cooling and plumbing company in Chantilly, serving Great Falls and the rest of Northern Virginia. Virginia contractor license #2705192276. 5.0 stars across 1,132 reviews on Google, Angi, Yelp, the BBB and Facebook. SwiftPro maintains a dedicated HVAC team and a dedicated plumbing team.
From SwiftPro Heating, Cooling & Plumbing in Chantilly. Housing figures are the Census Bureau’s American Community Survey, 2020 to 2024, for each place named; permit, water and sewer facts link to each office’s own page and were checked in September and October 2026.