What's Required in Seattle
- A mechanical permit ($60.35 per unit plus 5 percent) is required to install, replace or substantially alter a furnace, heat pump, wall furnace, space heater or woodstove insert, including attached ducts and burners.
- A new or altered circuit needs an SDCI electrical permit pulled by a licensed electrical contractor or the owner-occupant doing the work; reconnecting equipment to an unaltered lawful circuit is exempt.
- New or altered gas piping needs a gas piping permit from Public Health Seattle and King County ($137 plus $27 per outlet in 2026).
- Electric primary heat requires a Heat Equipment Sizing Form with the application.
- Exterior units must show their distance to the property line and meet the noise code; units over 400 pounds need engineered structural and seismic anchorage.
- Portable heating or cooling up to 3 kW or 10,000 Btu and 40 percent of the load, and like-in-kind thermostats, controls and motors of 10 HP or less, need no permit.
- Mechanical permits are valid for 18 months; renewals and change fees are one-quarter of the $292 base fee.
- Mechanical work reviewed with a building permit carries no additional mechanical fee.
Do You Need a Permit to Replace a Furnace or Install a Heat Pump in Seattle?
Yes, a mechanical permit from SDCI, and for a house or duplex it is one of the cheapest permits the city sells. The 2026 Fee Subtitle (Table D-8) charges $60.35 per unit for a forced-air furnace, heat pump, wall furnace, recessed wall heater, space heater or woodstove insert, including the ducts and burners attached to it, and the fee section says it applies to the installation, replacement or major alteration of heating equipment. With the 5 percent technology fee that is $63.37. Single-family and duplex furnace permits are online (OTC) permits under Tips 104 and 415, with no plan review. What adds cost is the other trades: a heat pump, mini-split or electric furnace needs an SDCI electrical permit for its new circuit, and any new or altered gas line needs a gas piping permit from Public Health Seattle & King County.
Seattle HVAC Permit Rules by Scenario
| What you are doing | City filing | Rule |
|---|---|---|
| Replace a gas furnace with a gas furnace on the existing circuit and gas line | Mechanical permit $60.35 + 5 percent = $63.37; no electrical permit if the circuit is unaltered | Table D-8; Seattle Electrical Code 80.50(B)(4) |
| Install a heat pump or ductless mini-split with a new outdoor unit and circuit | Mechanical permit $63.37 plus an online electrical permit (circuit $43.80 at 30-50 A; $105.12 minimum plus $55.48 admin) | Table D-8; Table D-15 items 7-8 |
| Extend a gas line or add a gas appliance outlet | Public Health gas piping permit: $137 plus $27 per outlet | PHSKC fee schedule (2026) |
| Add or rework ductwork as a separate job | Mechanical permit priced on value (Table D-2) plus hourly review, 1 hour minimum | Fee Subtitle 22.900D.090.B; Table D-2 item 4b |
| Portable or window units up to 3 kW or 10,000 Btu and 40 percent of the load | No permit | SRC R105.2 item 16 |
| Replace a thermostat, blower motor of 10 HP or less, control board or capacitor | No permit | Seattle Electrical Code 80.50(B)(3) and (6); SRC R105.2 item 18 |
| Outdoor unit near a property line, or any unit over 400 pounds | Show the property-line distance and meet the noise code; over 400 lb needs engineered anchorage | SDCI Mechanical Permit page |
How Much Does an HVAC Permit Cost in Seattle?
Furnace swap: $60.35 + $3.02 technology fee = $63.37. Reconnecting the furnace to its existing, lawfully installed circuit without altering it is exempt from an electrical permit under Section 80.50(B)(4) of the Seattle Electrical Code, and if the gas line is untouched Public Health is not involved. Heat pump: $63.37 for the mechanical permit plus the electrical permit for the new 30 to 50 amp circuit ($43.80) and any electric back-up heat of 3 to 15 kW ($23.36); those line items fall below the $105.12 online minimum, so with the $55.48 administrative fee and technology fee the electrical permit is about $168.63, for a total near $232. Gas furnace with new gas piping: $63.37 plus a Public Health gas piping permit of $137 + $27 for one outlet = $164, about $227. A job that needs all three permits lands near $400. Ductwork permitted on its own is value-based: the Table D-1 index plus a one-hour ($292) review minimum. Renewing a lapsed furnace permit costs one-quarter of the base fee ($73).
Who Pulls the Permits?
SDCI's mechanical pages do not restrict who applies for the furnace permit; the application is filed in the Seattle Services Portal with contractor information on the record. The electrical permit must be bought by a contractor with a Washington electrical contractor license and a Seattle business license, or by the owner-occupant doing the wiring personally. Gas piping permits from Public Health go to a registered contractor or a homeowner doing the work personally. Electric primary heat requires a Heat Equipment Sizing Form with the application. Exterior units must show their distance to the property line and meet the noise code, and any unit over 400 pounds needs a structural engineer's calculations for support and seismic anchorage.
Timing and Inspections
Online mechanical and electrical permits for houses issue immediately or the same day in the portal. Plan-reviewed mechanical permits, typical for commercial and multifamily buildings, take about 9 weeks, or 24 hours for a simple mechanical STFI. Mechanical permits are valid for 18 months. Schedule the mechanical final and the electrical cover and final inspections through the portal; Public Health inspects gas piping and needs several business days to schedule. Mechanical plans reviewed with a building permit, as in a remodel or ADU, carry no additional mechanical fee.
How to Get a HVAC Permit in Seattle
List the trades the job touches
Equipment replacement alone needs the mechanical permit; a new circuit adds an SDCI electrical permit; new or altered gas piping adds a Public Health gas permit.
Confirm who applies for each permit
The HVAC contractor or owner files the mechanical permit; only a licensed electrical contractor or the owner-occupant may buy the electrical permit; a registered contractor or homeowner gets the gas permit from Public Health.
Apply online in the Seattle Services Portal
Create a Trade and Construction permit, select the mechanical permit for a single-family or duplex furnace or heat pump, add contractor information and any Heat Equipment Sizing Form, and pay $60.35 plus 5 percent per unit.
Buy the electrical and gas permits
Purchase the online SDCI electrical permit for the new circuit (printed immediately) and apply in Public Health's Permit Center for gas piping before the work starts.
Schedule the inspections
Request the mechanical final and the electrical cover and final through the portal, and the Public Health gas inspection through its Permit Center, allowing several business days for the county inspector.