What triggers Seattle EV-ready / solar-ready requirements?

The 2021 Seattle Energy Code, codified at SMC Chapter 22.430 and adopted in March 2024 after a delayed roll-in, raises the bar on EV-ready and solar-ready electrical infrastructure for both new construction and substantial renovation. The triggers are scope-driven, not voluntary, and the code-compliance path is enforced by SDCI energy reviewers at permit submittal.

For EV-ready provisions, single-family new construction must provide a dedicated 208/240V branch circuit run from the panel to the parking area, including raceway, conductors sized for at least a 40-amp circuit, and an empty receptacle box at the parking stall. At least one parking stall is required to be EV-ready in single-family. Multi-family new construction scales the requirement: 40 percent of stalls EV-installed (charger present), 20 percent EV-ready (raceway plus conductors), and the remaining 40 percent EV-capable (raceway and panel capacity reserved). Commercial new construction follows a similar three-tier split keyed to occupancy type. The driving section is SEC C405.13 and the residential equivalent in SEC R404.

Solar-ready requirements (SEC C411 and R405) apply to most new buildings under three stories and require a designated solar-ready zone (a contiguous roof area cleared of HVAC, vents, and shading), structural capacity calculated for the future PV dead load, a labeled raceway path from roof to main service panel, and reserved electrical capacity at the panel sized for the anticipated PV system.

Substantial alteration triggers a partial application. The threshold is a renovation exceeding 50 percent of the building's gross floor area, or any change of occupancy that alters energy demand. In those cases, the EV-ready and solar-ready provisions apply pro-rata to the altered scope. A homeowner adding a 1,200 sq ft second story to a 2,000 sq ft Craftsman, for example, often pulls in the EV-ready circuit obligation even if the original house has no garage modification underway.

The one workflow shortcut: have the electrical engineer size the load calc once at schematic design with the EV and PV future loads stamped in. Retrofitting the panel later costs roughly 4x what reserving capacity costs upfront.