Furnace and AC replacement in Fairfax.
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.
- Your price range up front
- Sized to the house, not the old label
- Dedicated HVAC team
Get your new system priced
Two permit offices and two building booms behind one Fairfax address.
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.
The systems across Fairfax, place by place.
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. |
Fairfax houses, by the numbers
From the Census Bureau’s 2020 to 2024 survey, owner-occupied homes unless it says otherwise.
The City of Fairfax
- Median home built1966 Census
- Built before 1980about 7 in 10 Census
- Built since 2000about 2 in 10 Census
- Most homes aresingle-family houses, about 5 in 10 Census
- Heated withgas, about 7 in 10 Census
- Rentedabout 3 in 10 Census
- Houses this age are usually on their second or third system, often on the original ductwork.
- Most homes here heat with gas, so the usual pair is a gas furnace inside and an air conditioner outside, with the coil sitting on the furnace.
The Fairfax County side
Most of the Fairfax Station Census place, in the table, has Fairfax mail, so it counts here.
What a new furnace and AC costs in Fairfax.
$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
- Furnace alone, keeping your AC$4,285 to $14,040
- Heat pump system instead$8,499 to $21,650
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.
When replacing both makes sense in Fairfax.
Both halves are the builder’s, and the top floor runs warm
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.
Third system, original ducts
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.
The AC died and the furnace is the same age
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.
Who signs off on a new system in Fairfax.
City of Fairfax
The City of Fairfax runs its own permit office; a Fairfax mailing address outside the city line goes through Fairfax County. Source.
Fairfax County
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.
How to pick who replaces your furnace and AC in Fairfax.
Ask every company that quotes the job, us included.
Did they check the ductwork in an older City house?
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.
Do they size it to the house, or copy the old label?
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.
Is the whole job in the written price?
Furnace, outdoor unit, matching coil, refrigerant lines, thermostat, permit and hauling the old one away. If it isn’t on the paper, ask.
Already holding another company’s quote?
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.
What our customers say.
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.
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Furnace and AC replacement questions from Fairfax.
Does a new air conditioner in Fairfax County need anything for the new refrigerants?
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.
Is it worth pricing a 1990s furnace and AC in Fair Lakes before they fail?
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.
How much does a new furnace and AC cost in Fairfax?
$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.
Do I have to replace both at the same time?
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.
More from SwiftPro in Fairfax.
More from SwiftPro in Fairfax
Start with your number, then a written quote.
Call, book online, 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 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 884 Google reviews. SwiftPro maintains a dedicated HVAC team and a dedicated plumbing team.
SwiftPro Heating, Cooling & Plumbing, 4230 Lafayette Center Dr, Suite N, Chantilly, VA 20151, (703) 997-9757. Book online, read our reviews, or see every town we serve.