Washington’s EV fleet: a decade of fast growth, now flattening
The Washington Department of Licensing keeps a running count of every electric vehicle registered in the state, and it makes for one of the cleanest adoption curves you’ll find: a physical count of cars on the road, not a survey or a projection. At the end of May 2026 there were about 280,000 registered EVs in Washington — battery-electric and plug-in hybrid combined — up from just 22,000 at the start of 2017. That’s nearly a 13-fold increase in nine years. King County holds about 136,000 of them, just under half the statewide fleet, which tracks its share of the state’s wealth, its charging density, and its politics.
The news in this update is the shape of the last year. For most of the decade the line bent upward — each year’s gain bigger than the last. That has stopped. Growth has decelerated sharply, and in May 2026 the statewide fleet actually dipped for the first time in the series’ history outside the 2020 shutdown, slipping about 1,200 vehicles from its April peak. Year-over-year the numbers are still positive — +13.5% statewide, +10.2% in King County — but the monthly pace that produced those gains has largely evaporated. One month doesn’t make a trend, and a registration count can be revised, so the honest read is “flattening, watch it,” not “falling.” But the flattening is real and it is recent.
Underneath the total, the plug-in hybrid is fading. Battery-electric vehicles are now about 80% of the fleet (roughly 225,000) and still creeping up; plug-in hybrids (about 54,000) peaked in early 2026 and have been shrinking since. So the plateau in the headline number is really two stories at once — battery-electric growth cooling, and plug-in hybrids in outright decline — converging into a curve that, for the first time since these cars showed up in Washington, has stopped bending toward the sky.
Source: Washington State Department of Licensing, Electric Vehicle Population, via data.wa.gov (dataset 3d5d-sdqb). Count of EVs registered in Washington at each month-end (filtered to registration state = WA; King County is the county cut). Battery-electric + plug-in hybrid. Data refreshes monthly on the next daily build. State downturn shaded from FRED WAPHCI.