This is a market test, with the automaker building just 700 of the hybrid pickups — 500 Silverados and 200 Sierras.
The trucks, which are equipped with a 5.3-liter V8 engine, deliver a 13 percent improvement in city fuel economy, according to GM.
Estimated fuel economy on the two is pegged at 18 mpg in city driving and 24 mpg on the highway, a 2 mpg improvement. The EPA has not rated the hybrid trucks.
Based on consumer feedback, production of the trucks will be adjusted for the 2017 model year, General Motors said on Thursday.
The eAssist mild hybrid system will add $500 to the bottom line. Formal pricing on the trucks has not been announced.
Chevrolet spokesman Monte Doran told Edmunds the 2016 Silverado with eAssist will be priced at "an estimated $42,000."
The Sierra hybrid is likely to carry a sticker price of around $50,000.
The Silverado with eAssist is based on the two-wheel-drive Silverado 1500 crew cab in 1LT trim. It includes an eight-speed automatic transmission and is bundled with the "All-Star" equipment package that adds items including a tonneau cover and bed lights, Doran said.
The new eAssist powertrain is available in the Sierra SLT crew cab with the Premium Plus package that adds a long list of items, including a Bose premium audio system and rearview camera.
The eAssist system features a lithium-ion battery pack that adds approximately 100 pounds to the trucks' weight. The pack is located under the center console or front bench seat and uses the same battery cells as the Chevrolet Malibu Hybrid.
The trucks also are equipped with GM's Active Fuel Management system that shuts off four of the engine's cylinders at highway cruising speeds to boost fuel economy.
GM's hybrid trucks hit the market at a time when gas prices are below $2 a gallon and shoppers are putting larger vehicles, including trucks and SUVs, at their top of their lists.
Edmunds says: The launch of these hybrid trucks, which top other rivals with V8 engines when it comes to fuel economy, will be closely watched to see whether consumers are willing to pay a premium to save at the pump.