Open 24/7 for emergencies
Replacing only the air conditioner in Herndon runs $5,942 to $14,450 installed, and the gas furnace stays. Inside the town, electric heat leads.
Price range
$5,942-$14,450
8yrs @ 7.99%
$84/mo
15yrs @ 9.99%
$64/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 1,131 reviews
One of our HVAC technicians moving a new condenser up a driveway, the van behind him.
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 central air conditioner on its own, keeping the furnace you have. A single-stage unit on a small house sits near the bottom; a variable-speed one on a big house, near the top.
A central air conditioner alone, keeping your furnace, installed
$5,942 to $14,450
or $99/mo at 0% APR for 60 months
An air conditioner and furnace together, installed
$8,898 to $23,000
or $148/mo at 0% APR for 60 months
A heat pump in the AC’s place, installed
$8,499 to $21,650
or $142/mo at 0% APR for 60 months
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 before anything is ordered.
With Comfort+ membership at $199 a year, the diagnostic visit is included, and half of each repair bill is banked toward replacing that system, up to $1,500.
What’s different in Herndon
Start with how the house heats, because in Herndon that decides whether you’re shopping for an air conditioner at all. Inside the Town of Herndon about six in ten owners heat with electricity, and the box out back in those houses is usually a heat pump, replaced as a heat pump at $8,499 to $21,650. The AC-only job belongs to the gas houses: a bit under four in ten inside the town, and on the county side, the majority in Floris and in McNair. There the furnace stays put, and the condenser plus the coil perched on that furnace are what change.
McNair, along Sunrise Valley Drive, is where builder air conditioners are coming due. Most of it went up after 2000, with 36 percent of its homes from the 2000s alone, so a condenser from those first years is near twenty summers. One installed before 2010 most likely carries R-22, and since that refrigerant left production in 2020, a leak on one turns into a question of how much old stock is worth buying. About 60 percent of McNair homes sit in condo and apartment buildings and 29 percent are townhouses, so the outdoor unit often stands where the association has a say.
Inside the town, about a quarter of the owner homes are townhouses, in a town where more than half of everything went up in the 1970s and 80s. Their condensers sit in a row behind the houses on small pads, and a new unit is often shaped differently from the one it replaces, so it has to fit the old spot and keep its clearances. If your house is in the Town’s historic district, there’s one more step: most exterior changes there need a Certificate of Appropriateness from the Historic District Review Board first. Back on the old pad, nothing outside changes.
Who signs off follows the town line. Inside it, the Town of Herndon’s own Building Inspections office issues the mechanical permit, wants the contractor’s state license with the application, and puts its review at about 14 business days, one more reason to price a tired unit in spring. Outside it, in Floris, Franklin Farm, McNair and Dranesville, the permit is Fairfax County’s. The county files a new AC under mechanical work, and since today’s units are charged with A2L refrigerant, it wants the A2L certification attached.
Neighborhood by neighborhood
Census figures for the owner-occupied homes in each place, and what that usually means for the AC that’s there now.
| Place | Median home built | Most homes are | Heated with | The AC there now |
|---|---|---|---|---|
| Franklin Farm | 1985 | single-family houses, about 9 in 10 | electricity, about 5 in 10 | Mostly electric heat, so the cooling is usually a heat pump. |
| Herndon | 1981 | single-family houses, about 4 in 10 | electricity, about 6 in 10 | Mostly electric heat, so the cooling is usually a heat pump. |
| Dranesville | 1984 | single-family houses, nearly all | electricity, about 6 in 10 | Mostly electric heat, so the cooling is usually a heat pump. |
| McNair | 2003 | condo and apartment buildings, about 6 in 10 | gas, about 7 in 10 | Condo and apartment buildings: compact condensers on shared pads and roofs. |
| Floris | 1990 | single-family houses, about 8 in 10 | gas, about 6 in 10 | 1980s and 90s houses, many on their second air conditioner. |
| Hutchison | 1979 | townhouses, about 5 in 10 | electricity, about 7 in 10 | Mostly electric heat, so the cooling is usually a heat pump. |
| Sully Square | 2015 | condo and apartment buildings, about 6 in 10 | gas, about 6 in 10 | Condo and apartment buildings: compact condensers on shared pads and roofs. |
By the numbers
From the Census Bureau’s 2020 to 2024 survey, owner-occupied homes unless it says otherwise.
Inside the town limits. Floris, Franklin Farm, McNair and Dranesville, on the Fairfax County side, are counted by the Census as places of their own.
When it’s time
In Floris the typical owner’s home dates from 1990 and in Franklin Farm from 1985, so the condenser out back is usually the house’s second, and one swapped in during the 2000s most likely holds R-22. If the tech finds a leak and quotes a recharge, ask what the next one will cost, and set both beside the price of a new AC on the furnace you have.
An air conditioner put in before 2010 most likely holds R-22, which hasn’t been made since 2020. A leak on one of those usually ends the repair road.
It’s the pump at the heart of the outdoor unit and its costliest part. Out of warranty on an older unit, the repair can come close to half the price of a new AC, the point where Goodman says replacing may be the better money.
Permits, locally
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.
Herndon mail covers two permit offices. A house inside the Town files with the Town of Herndon’s Building Inspections office; one in Floris, Franklin Farm, McNair or Dranesville files with Fairfax County, which wants the A2L certification. An installer who asks before quoting knows which paperwork the job carries, and whether a historic district review applies.
Ask how they picked the size. Copying the old nameplate repeats whatever was guessed when the house was built.
The outdoor unit and the coil on the furnace are rated as a pair. Ask whether the quote replaces both, and what happens to the line set.
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 1,131 reviews. Read them on our reviews page.
On spec and on price for our A/C replacement. Showed up on time and all went as promised
Where we work
Next door to Herndon: Reston, Sterling, Great Falls, Oakton and Chantilly.
Questions
If it’s a builder unit from the mid-2000s, that’s the easy window: no tenant waiting on cooling, and time for the association to approve the new condenser before it’s ordered. McNair is mostly rentals, so plenty of owners face the same call. Get the written price now, and if the unit is still sound, a $99 diagnostic will say so.
Check what heats the house. Franklin Farm splits close to half and half between heat pumps and gas furnaces. An outdoor unit that keeps running through January is a heat pump, and its replacement is a heat pump too, $8,499 to $21,650. If a gas furnace does the heating and the outdoor unit only cools, this is your page: an AC on its own, $5,942 to $14,450 installed.
$5,942 to $14,450 installed for a central air conditioner on its own, keeping the furnace you have; size and efficiency set where yours lands. An AC and furnace together run $8,898 to $23,000. The HVAC replacement cost estimator gives your house its own number.
It’s worth pricing. A heat pump cools exactly like an AC and also heats on mild days, so with your gas furnace it becomes dual fuel. A heat pump system runs $8,499 to $21,650 installed, and we’ll price it both ways.
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 AC 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 Herndon and the rest of Northern Virginia. Virginia contractor license #2705192276. 5.0 stars across 1,131 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.