IRC E3601 & E3602: Electrical Service & Panel

The electrical service is the power feed from the utility into your main panel, and Sections E3601 and E3602 of the International Residential Code (IRC) set how big it has to be and how it is installed. These sections decide the amperage rating, where the main disconnect goes, and how much open space has to stay in front of the panel so it can be worked on safely. This page covers the service size and panel rules that drive electrical design on a custom home.

What E3601 and E3602 require

E3601 covers the service: the conductors and equipment that bring utility power to the house. The headline number is the minimum rating. A one-family dwelling must have a service with a rating of not less than 100 amperes, three-wire. The service conductors then have to be sized to the home's calculated load, so a large house with electric heat, a pool, and EV charging needs a bigger service even though 100 amps is the floor.

E3602 covers the service equipment: the main panel and disconnect. The service disconnect has to be readily accessible, either outside or inside near the point where the conductors enter. Here is the service-rating requirement:

Services shall have a rating of not less than 100 amperes, 3-wire.

A second rule trips up a lot of installs: the working space. A clear area at least 36 inches deep, at least 30 inches wide (or the panel width if wider), and 6.5 feet tall must stay open in front of the panel, with room for the door to swing 90 degrees. You cannot bury a panel behind shelving or a water heater.

What it means for an Arizona custom home

In the Valley, 100 amps is rarely enough for a custom home. Air conditioning is the swing factor: in Phoenix and Scottsdale the AC load is large and runs hard, so even a modest custom home usually lands on 200 amps, and large or all-electric homes go to 320 or 400 amps, often with a meter-main and subpanels. A licensed electrician runs a load calculation under the IRC's Chapter 36 method to size it, instead of guessing.

For example, a 4,000-square-foot Scottsdale home with two AC units, a pool, a casita, and EV charging will typically need a 320- or 400-amp service, and the panel location has to keep that 36-inch working clearance in a garage or utility wall, often inside conditioned space so the gear is not baking in 115-degree heat. Plan the panel wall early; relocating a panel after rough-in to recover clearance is costly. For sizing, see what size electrical service does a custom home need in Arizona .

Edition note

The IRC's electrical chapters track the National Electrical Code (NEC). The 100-amp service minimum and the 36-inch working-space depth are stable across the 2018, 2021, and 2024 IRC. What changes between editions is which NEC cycle the requirements mirror, and a few cities adopt the standalone NEC separately from the IRC, so the adopted electrical code can differ from the building-code edition. The Arizona building code editions by city page lists the electrical code for each jurisdiction.

How it connects

The service E3601 sizes is what feeds everything else, including any rooftop solar tie-in under R324 and the HVAC load behind M1401 HVAC sizing . Enforcement runs through your local AHJ and its electrical inspector. If you are weighing panel upgrades, see what is a smart electrical panel and is it worth it in a custom home .

Source

Read the section on the official ICC site: 2021 IRC E3601 on codes.iccsafe.org . The ICC I-Codes are copyrighted, so only the short rating clause is excerpted; the explanation is ours.