Plan on a permit. An interlock kit and a generator inlet change how the service can be energized; they are optional-standby transfer equipment, not a hardware-store accessory. Most authorities having jurisdiction want an electrical permit, a listed kit on a listed panel, and an inspection before the inlet is used. Some also want the utility notified. This site will not invent a national fee or a national exemption for homeowners who “just bolt on a plate.”
The permit is also what keeps the installation from becoming a problem at sale or on an insurance claim. A licensed electrician typically pulls it, installs the inlet and kit, and meets the inspector. If your town is one of the few that says otherwise in writing, keep that writing.
A permit does not make a dryer-outlet backfeed legal. Size the generator with the calculator, place it outdoors, and read the page on whether an interlock meets code as transfer equipment in the eyes of the AHJ.
This is not a permit calculation, a utility approval, or a substitute for a licensed electrician, HVAC contractor, or the authority having jurisdiction. Panel Headroom is an independent educational site. It is not a utility, a certification body, or a contractor. Electrical and generator work that is done incorrectly can cause fire, shock, or carbon monoxide poisoning. Use the adopted electrical code and manufacturer instructions; pull permits where required.