Furnace and AC replacement in Chantilly.
Furnace and AC replacement in Chantilly runs $8,898 to $23,000 installed. Many South Riding pairs date from 2006 and are wearing out together.
- Your price range up front
- Sized to the house, not the old label
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Get your new system priced
Chantilly’s furnace and AC pairs, twenty years in and due together.
Chantilly built in two waves. In 20151 the typical owner’s house dates from 1987, and 6 in 10 went up between 1980 and 1999. In South Riding, across the county line in 20152, the typical one dates from 2006 and nearly 8 in 10 went up after 2000. Each wave got its furnaces and air conditioners in the same few years, and a pair installed together tends to age together.
South Riding is where that clock runs loudest right now. A builder’s furnace and air conditioner from 2006 are both about twenty years old, the end of the usual run for each. If one fails, the other is no younger, and the coil that ties them together sits on top of the furnace. Replace one now and the other next year, and somebody climbs into the same townhouse attic twice.
In 20151 the first systems from the 1980s and 90s are mostly long gone, and a second round put in fifteen or twenty years ago is reaching the same age. In a gas house there, replacing both halves at once opens a third option: a heat pump where the air conditioner was, paired with the new furnace. Washington Gas pays its customers more toward that dual fuel pair when the furnace is replaced in the same job than when the old one stays. Portions of Chantilly are on Columbia Gas instead, so check the bill.
The county line decides who signs off. South Riding is Loudoun County, whose fee schedule lists replacing central heating and air conditioning as mechanical equipment work, with the gas furnace on a gas permit of its own. 20151 is Fairfax County, and its rules are listed below.
The systems across Chantilly, 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 |
|---|---|---|---|---|
| South Riding | 2006 | single-family houses, about 5 in 10 | gas, about 8 in 10 | Townhouse systems: a furnace in a closet or attic, the air conditioner out back. |
| Chantilly | 1987 | single-family houses, about 6 in 10 | gas, about 5 in 10 | 1980s and 90s houses, most on their second furnace and AC. |
Chantilly houses, by the numbers
From the Census Bureau’s 2020 to 2024 survey, owner-occupied homes unless it says otherwise.
20151, the Fairfax County side
- Median home built1987 Census
- Built before 1980about 2 in 10 Census
- Built since 2000about 2 in 10 Census
- Most homes aresingle-family houses, about 6 in 10 Census
- Heated withgas, about 5 in 10 Census
- Rentedabout 2 in 10 Census
- Electric heat here usually means a heat pump with backup strips, which is priced as a heat pump system, not a furnace and AC.
20152, the South Riding side
- Median home built2006 Census
- Built before 1980hardly any Census
- Built since 2000about 8 in 10 Census
- Most homes aresingle-family houses, about 5 in 10 Census
- Heated withgas, about 8 in 10 Census
- Rentedabout 2 in 10 Census
- Many houses here still run the builder’s furnace and AC, and the two tend to wear out together.
- Townhouse furnaces sit in closets and attics, so the path in matters as much as the size.
What a new furnace and AC costs in Chantilly.
$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 Chantilly.
Two systems, both from the builder
Bigger South Riding single-family houses often run two systems, one for the main floors and one for the bedrooms, both installed the year the house was built. When one fails, price the other too: same age, same clock.
Your heat may not be a furnace
Where a lot of homes heat with electricity, the indoor half is often an air handler, and the like-for-like swap is a heat pump system, $8,499 to $21,650 installed.
Both halves went in with the house
Plenty of houses built since 2000 still run the builder’s furnace and AC. They wear out on about the same schedule, so when one goes, price the pair.
Who signs off on a new system in Chantilly.
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.
Loudoun County
Loudoun County requires a permit to swap a gas water heater or furnace. Since October 2025, a replacement that keeps the same BTUs in the same spot needs no plans. Source.
How to pick who replaces your furnace and AC in Chantilly.
Ask every company that quotes the job, us included.
Did they say what happens to the refrigerant lines?
In a three-level townhouse the copper lines between the outdoor unit and the coil often run inside finished walls. Ask whether the quote reuses them, flushes them or replaces them, and why. It changes the price and how much drywall gets opened.
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.
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Furnace and AC replacement questions from Chantilly.
How do I get my own number instead of the range?
Take the HVAC replacement estimator. It asks about the house and the system you have now, and prices it from the same book as $8,898 to $23,000. When you’re ready, a tech comes out to measure, and you see the installed price on paper before you decide.
Will a new system work on my 1987 Chantilly ductwork?
Usually, once somebody measures it. Many 1980s houses here pull all their return air through one big hallway grille, and a new system is only as good as the air it can pull. Ask for a static pressure reading on the old system before the new one is sized; it shows whether the ducts need work first.
How much does a new furnace and AC cost in Chantilly?
$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.
Furnace and AC replacement in the towns next door.
- Furnace and AC replacement in Centreville
- Furnace and AC replacement in Catharpin
- Furnace and AC replacement in Herndon
- Furnace and AC replacement in Aldie
- Furnace and AC replacement in Oakton
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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 Chantilly 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.