Not always. As of October 2026, state law (Government Code §66311.5) bars a utility from requiring a new or separate connection for an ADU created within existing space, such as a garage conversion, unless it is built with a new house. For other ADUs, like a new backyard cottage, the utility may require one and charge a proportionate fee.
Which ADUs are protected from a separate connection requirement?
The protection covers ADUs and junior ADUs created inside an existing or proposed single-family home or an existing accessory structure, such as a garage conversion. For these, as of October 2026, the utility cannot require a new or separate direct connection, or impose a related connection fee or capacity charge. The exceptions are a unit built at the same time as a new single-family home, or one that is later sold separately.
When can a utility require a separate connection?
For other ADUs, such as a new detached cottage or an attached addition, a utility may require a new or separate connection. As of October 2026, any connection fee or capacity charge must be proportionate to the unit's burden on the system, based on its size or plumbing fixture count, and cannot exceed the reasonable cost of service.
Can a utility charge a connection fee for an ADU?
As of October 2026, an ADU or junior ADU cannot be treated as a new residential use for connection fees or capacity charges unless it is built with a new single-family home. Where a separate connection can be required, the proportionate-fee rule above applies.
Even without a separate meter, what utility work is common?
HCD's garage conversion guidance lists an electrical load calculation to see whether the existing service can carry the new unit. Many projects need a new main service and a subpanel for the ADU. Water, sewer and gas lines may need upsizing. Each utility sets its own service rules, so we confirm requirements with your providers during design.
Should I add separate meters even if they are not required?
It depends on how you will use the ADU. Separate meters let a tenant pay their own bills directly, but they add cost and may require a larger service or new equipment. For an ADU used by family, sharing one meter is often simpler. Some approvals near the coast have gone the other way: in an October 2025 Seal Beach case, Coastal Commission staff required separate meters as a condition. See ADUs in Seal Beach.
When does it depend?
It depends on the ADU type, whether a new house is being built at the same time, and your plans for renting or selling. A garage conversion for a family member is the simplest case. A new detached rental unit is where separate connections and fees are most likely. We price utility work into the written quote so it is not a surprise.
Related
Sources, as of October 2026: California Government Code §§66311.5 and 66323 (as amended by SB 543, effective January 1, 2026); HCD guidelines for garage conversion ADUs; California Coastal Commission staff report Th9a (October 2025).
Updated October 2026