What electric-ready wiring is required if my new ADU uses gas appliances?

If your newly constructed detached ADU uses a gas or propane water heater, furnace, cooktop or clothes dryer, the 2025 Energy Code requires you to prepare for a future electric replacement. In practice that means a dedicated 240-volt circuit near each gas appliance and reserved breaker space in the panel. The CEC confirms these electric-ready rules (Sections 150.0(n) and 150.0(t) through (v)) apply to new detached ADUs.

Requirements by appliance

• Gas furnace (150.0(t)): a dedicated 240V branch circuit within 3 feet of the furnace, with conductors rated at least 30 amps, a blank cover labeled "240V ready," and a reserved double-pole breaker space in the main panel marked "For Future 240V use."
• Gas cooktop (150.0(u)): the same setup within 3 feet of the cooktop, with conductors rated at least 50 amps.
• Gas dryer location (150.0(v)): the same setup within 3 feet of the dryer location, with conductors rated at least 30 amps.
• Gas water heater (150.0(n)): a reserved space at least 2.5 feet by 2.5 feet by 7 feet tall for a future heat pump water heater, plus wiring and plumbing that depend on where that space is. If it is within 3 feet of the water heater, you need a 120V/20A receptacle, a 240V-capable branch circuit rated at least 30 amps with the unused conductor labeled "spare," a reserved breaker, and a condensate drain no more than 2 inches above the heater base. If it is farther away, the code adds a labeled 240V circuit within 3 feet of the space and requires the cold and hot water piping to be routed through it.

Gas is not the prescriptive baseline

Electric-ready wiring is only part of it. The 2025 prescriptive path calls for a heat pump for space heating and a heat pump water heater. A gas furnace or gas water heater in a new ADU generally means using the performance path and making up the difference elsewhere in the design. Many cities also have local all-electric rules that go further than the state code, so check yours before you choose gas.

Does this apply to attached ADUs and garage conversions?

Additions must meet the mandatory measures in Sections 150.0(a) through (n), (p) and (q). That list includes the water heater rules in 150.0(n), but not the furnace, cooktop and dryer rules in 150.0(t) through (v). On the prescriptive path, an additional water heater in an addition must be a heat pump water heater or another option allowed by Section 150.2(a)1D. Ask your building department whether it expects any other electric-ready items on an addition.

What this means for your MEP plans and Title 24 report

The electrical plans must show each 240V-ready circuit, its rating, the labels and the reserved panel spaces. The load calculation and panel schedule must leave room for them. The plumbing plan must show the routing to the future heat pump water heater space where required. The CF1R lists gas equipment and its electric-ready status, so all three sheets have to match. See electrical plans, the ADU Title 24 guide, and how all-electric rules affect ADU electrical planning.

Sources: energy.ca.gov, energy.ca.gov, energy.ca.gov.