What the permit covers
From DPS's Residential Mechanical Permit page (read 24 October 2026):
| Job | Permit? | What DPS asks for |
|---|---|---|
| Replace a furnace, heat pump or AC | Yes, mechanical | The application and fee |
| Install or add ductwork | Yes | "ACCA Manual J Calculations (Eighth edition)"; without them "the application will not be processed" |
| Install or relocate an outdoor unit or tank | Yes | A marked site plan showing zoning setbacks |
| Boiler under 350,000 BTU, range hood, fuel-oil tank and piping, LP-gas tank and piping | Yes, mechanical | As above |
| Natural gas piping | Not DPS | WSSC Water issues plumbing and gas-service permits |
The page refers to a separate DPS "Who Can Apply for Permits?" document for who may apply. Maryland licenses HVACR contractors statewide; the state board's county page names only Anne Arundel and Prince George's as also requiring a county HVACR license, so a Montgomery job needs the state license. A new heat pump that needs a new circuit also needs an electrical permit.
Fees
From DPS's electrical and mechanical fee schedule, "Effective July 1, 2026 – June 30, 2027":
| Fee | FY27 |
|---|---|
| Minimum fee, one- and two-family homes (plus equipment fees) | $80.84 |
| Heating equipment | $28.61 per 100 MBH or fraction |
| Cooling equipment | $28.61 per five tons or fraction |
A typical house swap of an 80 MBH furnace and a 3-ton AC adds one heating and one cooling fee to the minimum. DPS says the schedule is for estimation and it calculates the final fee at issue.
How to apply
- Apply online; plans and Manual J go through DPS ePlans. A non-refundable filing fee is due at application.
- Pay by card or electronic check.
- Obtain "All required inspections", scheduled through DPS eServices or 311 (240-777-0311).
What 15,557 Montgomery County HVAC permits show
From Montgomery County HVAC permits, October 2024 to September 2026:
| Measure | Montgomery County HVAC |
|---|---|
| Issued | 15,557 (27% of all county permits) |
| Last 12 months / 12 months before | 7,607 / 7,950 (−4%) |
| Finished, permits issued Oct 2024–Sep 2025 | 73.2% |
| Usual days, issue to final (middle half) | 55 (18–120) |
| Busiest / quietest month (index) | June (125) / November (80) |
| ZIPs with the most | 20854 (1,254), 20817 (1,215), 20815 (832) |
HVAC permits have the lowest finished share of the county's big categories: 73.2%, against 79.5% for electrical and 80.7% for solar. An HVAC swap is quick, so a permit still open months later usually means nobody called for the final. Ask the installer to schedule it before the last payment. April to July all run 13% or more above an average month; November is the quiet one. More on county permit statistics, how long permits take and browse county permits.
Before you hire
Look up the address in DPS eSearch with the Montgomery County building permit search guide. National rules: HVAC replacement, a gas line. Costs elsewhere: HVAC replacement cost.
What this does not tell you
The county's files name no contractor and HVAC permits carry no job value, so there are no firm lists or costs. Gas work at WSSC Water is not in the file. Rockville and Gaithersburg permits are largely missing.
How we know this
Rules are quoted from DPS's Residential Mechanical Permit Process page and FY27 Electrical and Mechanical fee schedule, and the Maryland HVACR board's County License/Permits page, read 24 October 2026. Our counts are dataMontgomery's Mechanical Permits, read 19 October 2026: permits issued October 2024 to September 2026; days to final use permits issued October 2024 to September 2025.
Numbers come from public permit records in 57 cities, data through October 19, 2026. Nobody paid to be on this page and nobody can.
Questions
- Do I need a permit to replace a furnace or AC in Montgomery County, MD?
Yes. DPS requires a mechanical permit to erect, install, enlarge, alter, repair, remove, convert or replace an HVAC system, and its list includes furnaces, heat pumps, air-conditioning units, boilers under 350,000 BTU and fuel-oil tanks.
- How much is an HVAC permit in Montgomery County?
The FY27 schedule lists an $80.84 minimum for one- and two-family homes plus equipment fees: $28.61 per 100 MBH of heating and $28.61 per five tons of cooling. DPS calculates the final fee at issue.
- Do I need a Manual J for an HVAC permit in Montgomery County?
When ductwork is installed or added, yes: DPS requires ACCA Manual J calculations (eighth edition), and without them the application will not be processed.
- How long does an HVAC permit take in Montgomery County?
Applications are made online at any time. From issue to the county's final inspection, the usual HVAC permit issued October 2024 to September 2025 took 55 days, and 26.8% of them had no final a year or more later.
- Who handles the gas line for a new furnace in Montgomery County?
Plumbing and gas-service permits in the county are issued by WSSC Water, not DPS, so gas piping work is permitted there.
Build your own list
Pick your city and the kind of work. Every firm with a permit on record, sorted by what you value.
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