California ADU Shared Utilities: What Owners Should Put in Writing

Shared utilities create a billing question and a lease question

When an ADU and primary home share a utility account or meter, the parties need to understand who is the utility customer, what the rental agreement says, and how any tenant responsibility is calculated.

California DRE identifies utility responsibility as a term the rental agreement should address.

Write down the method before bills arrive

If the tenant will pay or reimburse a lawful share, document the agreed method clearly. Do not improvise a new formula after a large bill arrives without checking the agreement and applicable rules.

Local utility-billing or rent-regulation requirements can affect what is permitted.

Keep factual meter and billing records

Where meter readings are relevant, record the date, meter identifier and reading consistently. Keep underlying utility bills and any calculation used to derive a resident charge.

A transparent record is easier to review than a rounded monthly amount with no explanation.

Separate maintenance from allocation

A leak, faulty appliance, irrigation issue or equipment problem can drive consumption. Investigate unusual usage rather than automatically treating every increase as tenant consumption.