Do I Need a Permit to Replace My Furnace or AC in Wisconsin?

HVAC equipment replacement in Wisconsin requires a mechanical permit in most municipalities. This applies to furnaces, boilers, central air conditioners, heat pumps, and ductless mini-split systems — even when replacing with the same type of equipment in the same location. The permit ensures that gas connections, exhaust venting, condensate drainage, electrical connections, and combustion air supply meet current code requirements. Permit fees for HVAC replacement typically range from $50 to $300, depending on the municipality and scope of work. Milwaukee charges approximately $75 to $150 for a standard furnace replacement permit. Madison's fees are similar. Some cities offer expedited permit processing for straightforward equipment replacements, with permits issued in 1 to 3 business days. The inspection that follows installation checks proper venting (especially critical for gas furnaces to prevent carbon monoxide hazards), gas line connections, electrical connections, condensate drain routing, and thermostat wiring. If you are switching fuel types (e.g., oil to gas) or adding ductwork, additional permits and a more detailed plan review may be required. Wisconsin's minimum efficiency standards require 95% AFUE for gas furnaces in the Northern climate zone. Upgrading to high-efficiency equipment may qualify for Focus on Energy rebates.

Check Your Municipality

Permit requirements, fees, and exemptions vary by municipality. Verify the specifics for your location.