A 100 amp outdoor service disconnect is an exterior switch that shuts off utility power to a home, and the 2020 NEC requires one for new services.
For the full breakdown, see our best 100 Amp Outdoor Disconnect guide.
Two 2020 NEC rules settle what is a 100 amp outdoor service disconnect and when do you need one — and the second rule is why a routine panel swap can suddenly demand a new box on the outside wall. The device itself is simple. Knowing where the requirement lands, and how it talks to the service equipment you already own, is the part that trips people up.
100 Amp Outdoor Service Disconnects: What The Code Requires
A 100 amp outdoor service disconnect is a service-rated switch mounted outside that can cut power to every ungrounded conductor feeding the building. For one- and two-family dwellings, the 2020 NEC requires that switch — or an equivalent emergency disconnect — in a readily accessible outdoor location.
NEC 230.85 carries the emergency-disconnect rule:
