When should you investigate 400 amp residential service?

What makes a 400 amp assessment useful?

A combination of EV charging, electric heating with auxiliary heat, water heating, a shop, an addition or other significant loads can justify a coordinated review. The relevant inputs are the equipment and the accepted calculation, not floor area alone.

• Ask whether staged projects or load management change the recommendation.

Why do 320 and 400 amp terms appear together?

PSE’s single-family handbook distinguishes a 400 amp self-contained arrangement using a Class 320 meter base from a 400 amp current-transformer arrangement. They are different metering configurations.

• The terms are not permission to choose equipment from a shopping list; PSE, the designer and the AHJ determine the applicable design.
• Centralia’s service document also lists several requested service sizes.

Does a 400 amp service mean one panel?

Ask the designer to explain the distribution arrangement, including any multiple panels or feeders, the service disconnect and the capacity allocated to planned work. A proposal should identify the complete service equipment and not use “400 amp panel” as shorthand for an unspecified utility connection.

Which approvals belong in the estimate?

Utility engineering, equipment selection, permit and applicable plan review should be explicit. Tacoma’s published handbook and current permitting page use different review thresholds; confirm the project classification directly with Tacoma instead of assuming one universal threshold.

• Transformer or connection changes, route work and utility charges can materially change scope.

How do you avoid paying for an undefined capacity promise?

Ask for a written record of existing conditions, proposed loads, utility feasibility and the planned equipment arrangement. Identify which part is a contractor allowance and which is a separate utility estimate.

• Compare alternatives on the same intended loads and future work.
• The utility handbook’s example service bands do not establish the house’s calculated demand or an installed project price.
• Establish the accepted design before treating a large amp rating as a complete scope.

How should you compare 200 and 400 amp proposals?

Give both designers the same actual equipment list and ask for the capacity assessment supporting each recommendation. A house with planned EV charging and a heat pump still needs its particular loads evaluated.

• One proposal may assume auxiliary electric heat, another may omit a future water heater, and another may include a workshop.
• Reconcile those assumptions first.
• Comparing only the stated service ratings can hide the reason the prices and equipment differ.
• Square footage can be an intake fact without becoming a substitute for the load assessment.

What does the PSE handbook actually establish?

PSE’s single-family Electric Service Handbook 2026 lists service bands including 200 amps, 320 or 400 amps, and over 400 amps. It also says equipment power requirements affect service size.

• Its typical-use examples are utility guidance, not a Washington law requiring a particular rating for a floor area.
• The handbook asks about appliance loads, overhead or underground service, proposed panel size and connection point.
• Use those inputs to prepare engineering information, not to self-approve a service.

Why can the utility portion dominate the decision?

The utility must determine how the requested load can be served. PSE says engineering or a municipal right-of-way permit may be necessary where a transformer or service stubout is unavailable.

• Centralia evaluates modified service and prepares a cost estimate.
• Tacoma’s engineering review determines available service size and facility adequacy for added load.
• Ask what is already confirmed at the address and what is still contingent.
• A contractor cannot establish the upstream scope merely by naming a panel or meter socket in its own proposal.

How should plan review be kept separate from sizing?

Administrative review rules determine what documents or review a project needs. They are not a rule that a homeowner should choose the largest rating below a threshold.

• Tacoma’s handbook and current permitting page have differing review language, so the contractor must confirm the applicable project classification and review requirements directly.
• Elsewhere, Washington plan-review rules and the relevant AHJ may apply.
• The load basis, equipment design, utility feasibility and inspection requirements all remain necessary even when a project qualifies for an administrative exemption.

What makes an alternative worth comparing?

Ask the electrician whether a staged equipment plan, a different distribution arrangement or an accepted load-management approach changes the necessary service work. Compare the limitations as well as the initial price: what can operate together, what later equipment requires reassessment, and what utility or permit changes remain.

• The site does not claim that an alternative will work in every house.
• The useful result is a written explanation of the available design options and why the selected one serves the household’s stated needs.

What should be settled before approving the larger project?

The proposal should identify the service and metering arrangement, panels and feeders, utility engineering and charges, site work, permits, restoration and cutover dependencies. Ask for a clear treatment of allowances if utility review or concealed conditions are unresolved.

• Confirm what will count as completion and which final records you receive.
• A 400 amp label, a larger home and a bundled marketing price do not establish the same information.
• The direct contract should make the entire accepted arrangement legible before work proceeds.