HVAC replacement in Fairfax County, VA

Fairfax County's neighborhoods span many decades, so replacements here range from simple like-for-like swaps to systems that need duct, electrical or gas updates to work properly.

Permits in Fairfax County

Fairfax County Land Development Services requires a residential mechanical permit for new, replacement, repair or conversion of HVAC systems, and for gas piping to equipment. Electrical work is a separate trade permit, and a residential HVAC certification may be required.

Property owners may get permits in their own name, but the county strongly recommends that a licensed contractor be the responsible party. Inspections are required at each stage.

Homes in the towns of Herndon, Vienna and Clifton need approvals from the town as well. Herndon runs its own building inspections office, and the City of Fairfax has its own Office of Code Administration.

Ask every contractor whether the permit and inspections are included, and who handles any town approvals.

Utilities

• Electricity: most homes are served by Dominion Energy Virginia; NOVEC serves parts of Centreville and Clifton.
• Natural gas: most homes are served by Washington Gas; Columbia Gas of Virginia serves parts of Chantilly and Herndon.

Your utility matters for rebates, and for whether a heat pump, gas furnace or dual-fuel system makes the most sense for your bills.

Rebates and tax credits (as of November 2026)

• Federal tax credit: the 25C energy efficient home improvement credit, which covered heat pumps, central air and furnaces, ended for equipment placed in service after December 31, 2025. Systems installed in 2026 don’t qualify.
• Virginia home energy rebates: the state’s federally funded HEAR and HOMES programs are not open yet. Virginia Energy says launch depends on federal approval, and plans call for up to $8,000 toward a heat pump for income-qualified households. Work started before launch may not qualify.
• Washington Gas: customers can save up to $800 through the Home Energy Savings Program. In Virginia, the work must be done by a contractor in the program’s network.
• Columbia Gas of Virginia: up to $500 for a gas furnace rated 90% AFUE or higher in an existing home heated mainly by gas, bought and installed in 2026. Apply within 120 days or by January 31, 2027, whichever comes first. Funds are first come, first served.
• Dominion Energy Virginia: no rebate is currently listed for central heat pumps or air conditioners. Dominion offers smart thermostat rewards and an income- and age-qualifying program.

Rebate terms change often. Confirm the current terms with the utility before you buy.

What replacement costs here

In real Northern Virginia quotes we’ve reviewed, a complete furnace and air conditioner or dual-fuel replacement ran from $12,576 to $21,594. See what drives the price, and why quotes for the same house differ.

Older homes are more likely to need work beyond the equipment: undersized returns, older refrigerant lines, or electrical and venting updates. Those are exactly the items that make one quote look cheaper than another.

Before you sign

• Check the contractor’s Virginia license on the DPOR license lookup. HVAC work falls under the HVA specialty, and gas work under the GFC specialty.
• Make sure the size comes from a Manual J load calculation, not from the old unit.
• Get exact model numbers, and confirm whether the refrigerant lines and return ducts are included.
• Confirm the permit, inspection and labor warranty are in writing.

How 1Stop helps in Fairfax County

1Stop is an independent service based in Ashburn. We don’t install systems or work for any contractor. A Comfort Consultant visits your home, runs a Manual J load calculation and writes one scope of work. Licensed, insured local contractors bid on that same scope, and you compare every bid side by side. It’s free for homeowners. See a sample comparison.