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Furnace and AC replacement in Fairfax runs $8,898 to $23,000 installed, by size and efficiency, for a 1960s City house or a 1990s Fair Lakes townhouse.
Price range
$8,898-$23,000
8yrs @ 7.99%
$126/mo
15yrs @ 9.99%
$96/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
One of our technicians with a new Trane outdoor unit he just installed beside a Northern Virginia house.
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
$8,898 to $23,000 installed for a furnace and air conditioner replaced together, 2 to 5 ton, from the same price book as our estimator. Where you land depends on the size of the house, the efficiency you pick, and what the ductwork and venting need.
Furnace and AC together, installed
$8,898 to $23,000
or $148/mo at 0% APR for 60 months
Furnace alone, keeping your AC
$4,285 to $14,040
or $71/mo at 0% APR for 60 months
Heat pump system instead
$8,499 to $21,650
or $142/mo at 0% APR for 60 months
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 estimator gives your house its own number. Then we measure, and the price is in writing before anything is ordered.
Two years of labor come with every install. Monthly plans are on our financing page.
What’s different in Fairfax
Fairfax mail covers two places that built at different times. Inside the City of Fairfax the typical owner’s house is from 1966 and about 7 in 10 predate 1980, so most are on their third system or later, still moving air through ducts laid out for the first. Out on the county side, about 7 in 10 homes went up after 1980, and in Fair Lakes, Fair Oaks and Navy plenty still run the furnace and air conditioner the builder put in.
Those builder systems wear out together, which is the case for replacing both at once. The coil for a new air conditioner sits on top of the furnace, so a new outdoor unit means opening the furnace closet anyway. If the furnace beside it is the same age, doing both is one permit, one inspection and one disruption instead of two.
Kings Park West is where the like-for-like swap is often a heat pump instead. Close to half its homeowners heat with electricity, and a 1970s house there with an air handler where a furnace would be usually gets a heat pump system, $8,499 to $21,650 installed.
Merrifield and Fair Oaks are condo country: most Merrifield homes are in condo and apartment buildings, and about half of Fair Oaks. There the outdoor unit may share a pad or a roof with the neighbors, and the association usually wants to approve the new one before it goes in.
Neighborhood by neighborhood
Census figures for the owner-occupied homes in each place, and what that usually means for a replacement.
| Place | Median home built | Most homes are | Heated with | What the system usually is |
|---|---|---|---|---|
| Fair Oaks | 1995 | condo and apartment buildings, about 5 in 10 | gas, about 6 in 10 | Condo closet systems: small units, often with association rules for the outdoor half. |
| City of Fairfax | 1966 | single-family houses, about 5 in 10 | gas, about 7 in 10 | Second or third systems, often on the original ductwork. |
| Fairfax Station | 1982 | single-family houses, about 9 in 10 | gas, about 5 in 10 | 1980s and 90s houses, most on their second furnace and AC. |
| Kings Park West | 1976 | single-family houses, about 7 in 10 | gas, about 5 in 10 | Second or third systems, often on the original ductwork. |
| Merrifield | 1990 | condo and apartment buildings, about 6 in 10 | gas, about 6 in 10 | Condo closet systems: small units, often with association rules for the outdoor half. |
| Fair Lakes | 1998 | townhouses, about 3 in 10 | gas, about 7 in 10 | 1980s and 90s houses, most on their second furnace and AC. |
| Long Branch | 1968 | single-family houses, about 9 in 10 | gas, about 7 in 10 | Second or third systems, often on the original ductwork. |
| Mantua | 1968 | single-family houses, about 7 in 10 | gas, about 7 in 10 | Second or third systems, often on the original ductwork. |
By the numbers
From the Census Bureau’s 2020 to 2024 survey, owner-occupied homes unless it says otherwise.
Most of the Fairfax Station Census place, in the table, has Fairfax mail, so it counts here.
When it’s time
A Fair Lakes or Navy townhouse on its original 1990s furnace and air conditioner, where the bedrooms never quite cool. Replacing the pair is the chance to size for the house as it is now, finished basement and all, not as the builder guessed.
An older house is usually on its third system, still on ductwork laid out for the first. We check the ducts and venting before sizing the new one.
A new outdoor unit needs a matching coil, and on a gas system the coil sits on the furnace. If the furnace is as old, do both and open that closet once.
Permits and sign-offs
The City of Fairfax runs its own permit office; a Fairfax mailing address outside the city line goes through Fairfax County. Source.
Fairfax County lists replacing a heating or cooling system as mechanical permit work. Source.
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.
Fairfax County asks for an A2L refrigeration system certification with the permit for any heat pump or air conditioner that runs on the newer A2L refrigerants. Source.
Our Virginia Class A contractor license, 2705192276, is on the side of the van.
Choosing who installs it
Ask every company that quotes the job, us included.
A 1960s house’s ducts were laid out for a furnace alone, before anybody added air conditioning. Ask whether they measured the return and the supply runs before sizing the new system. Bigger equipment on small ducts is louder and cools worse.
The old size is a guess somebody made years ago. Ask whether they measure the house and check the ductwork first. Too big short cycles; too small runs all afternoon in August.
Furnace, outdoor unit, matching coil, refrigerant lines, thermostat, permit and hauling the old one away. If it isn’t on the paper, ask.
Our free second opinion looks at the system you were quoted on and tells you what it actually needs, with our price if you want it.
Two of our crew going over a work order before the day's calls.
The system we put in first
Built to take a beating. Put in by our crew.
Heat lamps, snow and rain on one outdoor unit: that’s Trane’s own film. We’re a Trane Comfort Specialist, on Trane’s own dealer locator, and when you pick a Trane, our crew puts it in.
Films: Trane’s own.
From our Google reviews
5.0 stars across 1,132 reviews. Read them on our reviews page.
I would gladly recommend them to anyone in the greater Fairfax/Alexandria area without reservation.
Swiftpro came out the same day I called when my AC was out and had it fixed in less than an hour after arriving.
Rich did a great job. We hit it off very well. He was on time, and we promptly gathered the necessary measurements. He explained all the details. He prepared the estimate while at the house. This work is for a HVAC full replacement.
Questions
Yes. Fairfax County asks for an A2L refrigeration system certification with the permit for any heat pump or air conditioner on the newer A2L refrigerants, which is what new systems run on now. Inside the City of Fairfax, the City’s own permit office sets what it asks for.
Yes. A replacement on your schedule gets measured and sized properly; one forced by a failure in August gets decided in a hurry. Start with the HVAC replacement estimator for your range, and if a repair comes up first, the diagnostic visit is $99.
$8,898 to $23,000 installed for the pair, by size and efficiency. A furnace alone, keeping your AC, is $4,285 to $14,040. The HVAC replacement estimator gives your house its own number.
No. If the AC is young and only the furnace failed, replace the furnace. If they’re the same age, do both: a new outdoor unit needs a matched coil, and one built for the old refrigerant isn’t rated for the new one.
Ready when you are
Call, send the form at the top, or take the HVAC replacement estimator first. We measure before we quote, and if a repair makes more sense than a new system, 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 Fairfax 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.