When should I ask about 400 amp service?
A combination of heating, EV charging, electric water heating, workshop or addition loads may justify a 400 amp review. The electrician should assess the planned equipment using an accepted calculation.
- The assessment should also consider whether another arrangement could work and which future projects are included.
Which meter configuration would my utility require?
PSE distinguishes a Class 320 self-contained meter arrangement for a 400 amp service from current-transformer metering; Centralia lists service requests for both 320 and 400 amps. The utility, designer and electrical inspection authority determine which arrangement applies to your address.
What should a 400 amp estimate include?
A 400 amp estimate should cover service equipment, distribution panels and feeders, utility engineering, possible connection or transformer work, permits, site restoration and outage coordination. In Tacoma Power territory, confirm the applicable engineering-review threshold with the utility before finalizing the scope.
- The panel enclosure may be only one part of the upgrade.
What needs agreement before equipment is ordered?
Ask for the proposed metering and distribution arrangement, which party has accepted it and which approvals are still outstanding. Establish whether the utility’s connection facilities can support the request and whether transformer or route work is included.
- The contract should say how project-specific utility charges and changed site conditions will be handled.
- Confirm utility approval, equipment availability and the outage date before committing to installation.
Sources and scope
Primary-source research reviewed October 17, 2026 for 400 amp residential electrical service in washington. Code, utility standards and administrative guidance have different roles. Confirm current requirements for the project address.