Whole-house battery backup and generator transfer switches in Seattle and Puget Sound

Why the lights go out here in the first place

Puget Sound outages are a wind-and-trees problem more than a grid-capacity problem. Windstorm season runs from roughly October through January, and the lines on most residential streets sit beneath tall second-growth conifers now well above the wires. One Douglas fir across a primary drops an entire feeder, and utilities restore the largest feeders first. That is why a wooded cul-de-sac is often among the last addresses back, and why multi-day events happen here in a way they do not in denser, undergrounded neighborhoods.

Before picking equipment, write down the circuits you actually need: the furnace or heat pump air handler, the refrigerator, a well pump, the network gear, and a few lights and receptacles. That list sets the tier.

How the options compare

Option	Backed-up loads	Transfers	What limits it
Generator inlet with a panel interlock	Any circuit in the panel, to the generator’s rating	By hand	Fuel on hand
Six-circuit manual transfer switch	Six circuits chosen in advance	By hand	Fuel on hand
EcoFlow Smart Home Panel 2 with a Delta Pro Ultra	Twelve circuits on the smart panel	Automatic	Battery capacity; recharges from grid, generator or solar
PSE Flex-eligible battery	Loads on a protected backup subpanel	Automatic	Battery capacity; recharges from grid or solar
Standby generator with an automatic transfer switch	The backup subpanel, or the whole panel	Automatic	Gas supply

Option 1: a generator inlet with an interlock, or a six-circuit transfer switch

The cheapest permanent answer. An inlet box goes on an exterior wall, conduit runs to the panel, and a backfeed breaker gets a mechanical interlock plate: a metal slide that makes it physically impossible to have the main breaker and the generator breaker on at once. You roll out a portable generator, plug in, open the main, switch on the circuits you want, and refuel it as the outage runs. Fuel is the only thing limiting runtime.

One constraint decides this tier: interlock kits are panel-specific. They are listed by panel brand and catalog number, and some panels, older load centers in particular, have no listed kit at all. Then the answer is a manual transfer switch wired to a fixed set of circuits. The Issaquah job below is a Nature’s Generator six-circuit non-automatic transfer switch, flex conduit to the main panel, circuits picked off the panel directory before anything was cut in.

Option 2: EcoFlow Smart Home Panel 2 with a Delta Pro Ultra

This is the system we have put in twice. The Smart Home Panel 2 mounts beside the existing load center and takes twelve branch circuits onto relay modules, with separate grid and generator inputs and a communications section carrying LAN, RS485 and EPO terminals. Delta Pro Ultra inverter and battery stacks sit on the floor and connect back to the panel’s base. When the grid drops, the panel transfers those twelve circuits by itself. Nobody has to be home.

Both are in the gallery. In Seattle in December 2025 the smart panel went in over a new 100 A subpanel, alongside a 50 A generator inlet with an interlock and a 60 A EV charger circuit, so the house can ride on battery, on a generator, or both. In Puyallup that same month a Delta Pro Ultra inverter went on four stacked battery modules.

Twelve circuits is not a forty-space panel. A large continuous draw, an EV charging at 48 A, a resistance water heater, a hot tub, either stays off the backed-up side or gets scheduled around. Choosing the twelve is the real design work.

Option 3: PSE Flex-eligible batteries, and the trade-off nobody mentions

Puget Sound Energy serves Bothell, the Eastside, most of south King County and Pierce County outside Tacoma. Its Flex programme is the only battery incentive on this corridor as of September 2026; Seattle City Light, Snohomish County PUD and Tacoma Power pay nothing for storage, so in Seattle or Tacoma the choice comes down to hardware. The eligible brands, the amounts and the pre-approval requirement are on the incentive table on this page.

EcoFlow is not eligible. Make that trade deliberately: EcoFlow is the lower-cost, modular route with no incentive attached, while a Powerwall 3 or a FranklinWH costs more up front and can earn the enrollment rebate plus the annual demand-event payments. PSE sets conditions on who installs the equipment, so settle that before counting the money.

We have not installed a Powerwall 3 or a FranklinWH, and there is no photo of one here.

Storage on a small commercial meter

Behind a commercial meter the math changes, because the Section 48E investment tax credit covers 30% of installed cost and runs through 2033. It applies to commercial energy storage, not to a house. We do not give tax advice, so ask your tax advisor whether your project qualifies. The electrical work keeps the same shape: a protected subpanel, a transfer point, and a load study.

Who issues the permit, and what the line item costs

WAC 296-46B-901 puts the electrical permit on the contractor, not on you, and it is bought before work starts. Which office issues it depends on the address: Seattle SDCI inside Seattle, Tacoma Power inside Tacoma, several Eastside and Snohomish cities that run their own electrical permitting, and Washington L&I everywhere else. The FAQ on this page names which is which.

Where L&I is the authority the fee schedule is public. Effective 1 July 2026, a generator with transfer equipment up to 100 A is $109.90. A first panel with up to five circuits is $100.50, and each additional circuit is $8.20. Those are pass-through figures with their own line on the quote.

What is in the gallery, and what is not

Two EcoFlow Smart Home Panel 2 systems, Seattle and Puyallup, both December 2025, and the Issaquah manual transfer switch from August 2026. The Kent photo is a panel replacement, not a backup job. It is here on purpose: plenty of backup projects start with an old load center that has no spare double-pole slot for a backfeed breaker.