The short answer
Plan utilities early: they're a common source of delay and surprise cost. An ADU can usually share the house's electric service; a separate meter needs its own address. A new detached ADU must have solar panels (on it or on the house) unless it's too small to need them, and new space heating is generally a heat pump. No law yet sets a firm deadline for utilities to connect an ADU.
Electricity
- LADWP (Los Angeles): one service per lot. A separate meter for the ADU needs its own legal address approved by the city, and meters are normally grouped at the main house (Electric Service Requirements, 2025). Start the request on LADWP's residential projects page, which has an ADU option.
- LADWP says a meter is generally installed within 10 working days once Building and Safety approves the service, if no other work is needed; underground service takes 6–8 weeks just for the cost estimate (LADWP FAQ).
- Power lines: an ADU under or near overhead lines must meet the state's clearance rules (General Order 95), and the owner pays any cost to meet them, including moving lines.
- SCE (Ventura County and other areas): request an ADU connection through its project portal. SCE reports an average of 160 business days from request to connection for new residential service of all kinds in 2024–25 (SCE posting).
Water and sewer
- LADWP can serve buildings on one lot through one water connection or give each building its own. For 2026–27, a new 1-inch service with a meter costs $7,407, plus a water main charge where it applies (LADWP charges).
- For an ADU made from an existing building, Los Angeles requires a separate electrical panel for the ADU, a water shut-off in the unit, and a sewer availability clearance (LADBS bulletin).
- State law limits connection fees: none for an ADU in existing space (unless it's built with a new house or sold separately), and a proportionate charge for other ADUs; see ADU fees.
Solar and the energy code
- Newly built ADUs have needed solar panels since 2020; under the current 2025 Energy Code (permits applied for since January 1, 2026), that's unless the required system would be under 1.8 kW or there's less than 80 square feet of usable roof (California Energy Commission). The state's ADU Handbook says the panels can go on the ADU or the main house.
- A detached ADU, or one joined to the house only by a breezeway, counts as new construction. An ADU sharing a wall with the house, a garage conversion or an ADU over a detached garage counts as an addition, and a conversion of existing living space as an alteration: those don't need solar.
- The standard design uses a heat pump for space heating and a heat pump water heater; smaller units have simpler water-heating options.
What the law says about utility timelines
Since January 1, 2026, utilities must post estimated fees and typical timeframes for new connections, including ADUs (SB 1210), but that isn't a deadline. SB 1196 (2026) directs the state to set connection timelines for investor-owned electric utilities, such as SCE, by September 30, 2027; it doesn't cover city-owned utilities like LADWP.
General information. Utility rules change; confirm requirements with your utility and building department before you design.
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