Do I need a permit to replace my HVAC?

Yes — like-for-like swaps (same fuel type, same capacity) require a mechanical permit in all 50 states. Cost: $150–$450. System-type conversions (gas to heat pump, oil to electric) usually require additional electrical permits and sometimes structural permits. Permit-driven inspections check refrigerant-line sizing, condensate-drain code, electrical disconnect placement, and combustion-air rules on gas equipment. Unpermitted HVAC work voids the equipment warranty (manufacturers require permitted install) AND voids your homeowners insurance for any HVAC-caused fire or water damage claim. Worth the $150–$450 every time.