Open 24/7 for emergencies
Replacing only the furnace in Herndon runs $4,285 to $14,040 installed when the air conditioner stays. Gas heat leads out in Floris and McNair.
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 Herndon
Inside the Town of Herndon a bit under 4 in 10 owners heat with gas. The rest mostly heat with electricity, and in a house here that usually means a heat pump with no furnace in it. Past the town limits gas gains ground: roughly 6 in 10 owners in Floris burn it, 7 in 10 in McNair, and Franklin Farm splits close to evenly. A handful of homes on both sides burn propane instead, and those furnaces are ours to replace too.
Most of those gas houses date from the 1980s and 90s. The typical owner’s home went up in 1985 in Franklin Farm and in 1990 in Floris, so whatever furnace sits there now is likely the house’s second, or its third. Outdoor units tend to quit sooner, standing in the weather all year, which can leave a house like these with an AC years newer than its furnace. That’s the furnace-only job: the younger air conditioner keeps its place, and the new furnace’s blower is matched to the coil riding on top of it.
McNair is the young end of the address. Its typical owner’s home dates from 2003; about 6 in 10 sit in condo buildings, and townhouses make up most of the rest. Furnaces there are compact closet and utility room units, many possibly still the builder’s and past twenty winters. A replacement has to clear the same doorway and fill the same footprint, and if its vent exits an outside wall, expect the association to weigh in.
Inside the town, the Town of Herndon’s Building Inspections office issues the permit. It puts mechanical and gas permit review at about 14 business days, and takes an emergency application for heat ahead of its usual tax and business license checks. Outside, Fairfax County requires a permit for every gas furnace swap, same size in the same spot included, along with a chimney vent certification. Our HVAC replacement cost estimator narrows $4,285 to $14,040 to your house.
Neighborhood by neighborhood
Census figures for the owner-occupied homes in each place, and what that usually means for the furnace that’s there now.
| Place | Median home built | Most homes are | Heated with | The furnace there now |
|---|---|---|---|---|
| Franklin Farm | 1985 | single-family houses, about 9 in 10 | electricity, about 5 in 10 | Mostly electric heat; gas furnaces are the minority. |
| Herndon | 1981 | single-family houses, about 4 in 10 | electricity, about 6 in 10 | Mostly electric heat; gas furnaces are the minority. |
| Dranesville | 1984 | single-family houses, nearly all | electricity, about 6 in 10 | Mostly electric heat; gas furnaces are the minority. |
| McNair | 2003 | condo and apartment buildings, about 6 in 10 | gas, about 7 in 10 | Condo and apartment buildings: compact furnaces in closets. |
| Floris | 1990 | single-family houses, about 8 in 10 | gas, about 6 in 10 | 1980s and 90s houses, many on their second furnace. |
| Hutchison | 1979 | townhouses, about 5 in 10 | electricity, about 7 in 10 | Little natural gas, so few gas furnaces. |
| Sully Square | 2015 | condo and apartment buildings, about 6 in 10 | gas, about 6 in 10 | Condo and apartment buildings: compact furnaces in closets. |
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
Both units carry a manufacture date on their labels. When the outdoor one is under ten years old and the furnace is original to a 1980s Franklin Farm or Floris house, a furnace by itself is the job worth pricing, and the air conditioner carries on beside it.
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
The Town’s plumbing and gas permit asks for a gas riser diagram for any new gas appliance or gas line, and the Town puts its review at about 14 business days. 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.
Washington Gas offers its own customers a rebate on a qualifying furnace at 95.1 percent AFUE or higher. Fairfax County says some Herndon homes buy gas from Columbia Gas of Virginia, though, and that rebate doesn’t reach them. Check the bill before the model gets picked.
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!
Where we work
Next door to Herndon: Reston, Sterling, Great Falls, Oakton and Chantilly.
Questions
Only if something changes outside. Reuse the old vent and the wall looks the same. Most high-efficiency furnaces, though, exhaust sideways through plastic pipe, and inside the Town’s historic district most exterior changes call for the Historic District Review Board’s Certificate of Appropriateness before work begins. If that pipe would be visible from outside, check with the Town first.
$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 Herndon 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.