Often, but not for every utility. Electricity and natural gas can usually be metered separately if the serving utility approves a second service. Water is harder: Seattle Public Utilities generally allows one domestic water service per legal parcel, so most Seattle ADUs share the house’s water meter. Sewer is rarely metered on its own at all.
The utility makes the call, and the answer affects panel design, trenching and the lease. This quick guide covers each utility, the trade-offs, and how to divide a shared bill.
The Utility Decides, Not the Permit
A meter belongs to whoever sells the service: in Seattle, Seattle Public Utilities for water and sewer and Seattle City Light for power. Elsewhere, Puget Sound Energy supplies gas across much of the region and electricity in many King County suburbs, Snohomish County PUD powers most of Snohomish County, and water comes from a city utility or a water district with its own policy.
Washington’s Department of Commerce, in its ADU guidance for local governments, recommends allowing shared meters, especially for attached units within the existing meter’s capacity. Sharing is a normal setup, not a shortcut.
Electricity Is the Easiest to Separate
Power is the utility most often split. A second meter means a new or modified service and an application with the utility; Seattle City Light requires an Electric Service Application for new construction and service changes, and its submittal resources include sample plan sets for a house with a backyard cottage.
The alternative is a subpanel fed from the main service, one bill, and an owner-installed submeter to track the unit’s share. Utility crews work on their own schedule, so apply early, not after framing.
Water Usually Stays on One Meter in Seattle
SPU’s water service rules provide one domestic water service per legal parcel, with narrow exceptions such as landlocked parcels and critical facilities, and SPU will not approve extra services just to bill owners or tenants separately. Customer-owned submeters can track use, but SPU does not read or bill them.
Other providers set their own policies, and wording can be mixed. Everett’s ADU guidance states that each dwelling unit requires its own water meter and service, yet also notes that ADUs typically share the main meter, with any submeter private and extra services available by application. On an Everett lot, confirm with the city’s utility staff which applies before the site plan is drawn.
Sewer and Gas Follow Their Own Rules
Sewer is billed rather than metered in most homes, and many utilities base the charge on water use, so the water arrangement usually decides how sewer is split. The pipe still matters: Everett requires a separate side sewer per unit, which may join an existing one downstream if the shared line is large enough. In Seattle, SDCI reports every ADU permit to King County for its sewage treatment capacity charge.
Gas is optional. Many new ADUs run entirely on electric heat pumps, which removes one meter question; if the unit will use gas, Puget Sound Energy reviews whether a separate meter can be set.
Shared or Separate: What Changes for Owners
Separate meters let a tenant hold the account and pay for exactly what they use. The cost is a new service, often a longer trench, possible connection charges and more coordination.
A shared meter is simpler and usually cheaper. It suits a parent, an adult child, a guest suite or a home office; for a rental, the owner carries the risk of heavy use unless the lease addresses it. Our guide to how utilities affect the asking rent covers the pricing side.
Fair Ways to Divide a Shared Bill
Include utilities in the rent, priced from a full year of bills.
Charge a fixed monthly utility amount set in the lease and reviewed yearly.
Bill measured use from a private submeter, with readings on each bill.
Apply a written formula, such as a split by occupants or floor area.
Seattle regulates third-party utility billing (SMC 7.25) where a property has three or more tenant units on shared service, which a fully rented house with two ADUs can reach; its disclosure and itemization rules apply to any formula you choose.
Settling the Meter Plan During Design
Meter choices shape the panel, the trench route and the utility applications, so settle them before drawings are final. Utilities open accounts by address; see getting an address for the unit. For the construction side of water, sewer and power, see what ADU utility hookups involve. To check sewer location, frontage and access on your parcel first, ask for a free lot report.
FAQ
Can an ADU tenant open an electric account in their own name?
Only when the unit has its own utility meter. With a subpanel and a private submeter, the account stays with the owner, and the tenant pays through the lease.
Can I bill a tenant from a private water submeter?
Generally yes, as a private arrangement written into the lease. In Seattle, the third-party billing rules also apply once a property has three or more tenant units on shared service.
Will adding an ADU require a larger water service?
Possibly. The designer totals the fixtures in both homes, and the water provider decides whether the existing service is adequate; in Seattle that runs through SPU alongside the building permit.
Can a basement ADU share the house’s electrical panel?
Sometimes. Everett’s guidance says separate panels are most common, but a shared panel is possible if every occupant has ready access to their own breakers.
Do separate meters make it easier to sell the ADU as a condominium later?
They simplify dividing costs between two owners, but a meter does not create a separate unit; the condominium documents still allocate shared expenses.