General Motors is electrifying its pickups.

A limited number of Chevrolet Silverados and GMC Sierras fitted with a mild hybrid system will be offered in California in 2016, with their production and availability to be adjusted in 2017 to meet demand.

The announcement was a surprise, and puts GM ahead of Ford and Ram, which both plan to introduce hybrid pickups within a few years.

The $500 option on two-wheel-drive crew cab trucks equipped with a 5.3-liter V8 includes a .45 kilowatt-hour battery pack located under the center console and a 13 hp electric motor attached to the engine’s accessory drive that also delivers 44 lb-ft of torque.

The electric motor will provide an assistive boost under acceleration, give the trucks automatic start/stop capability, and recharge the battery under braking. Unlike the two-mode hybrid pickups GM built from 2009 to 2013, the new trucks will not provide pure electric drive at any speeds.

Fuel economy is expected to improve by 13 percent, for a 2 mpg increase across the board in city, highway and combined ratings. This should translate to a fuel savings of approximately $150 annually at current prices.

Just 500 of the Chevys and 200 of the Sierras will be sold this year, all in California. GM will use the results of this small launch to determine how many trucks to build for 2017.