On paper, the 2011 GMC Sierra 1500 Hybrid seems like a perfect union: a full-size pickup that gets 20 mpg around town, using both a whomping V8 for proper truck labor and a pair of electric motors during the stop-and-go. It's a truck that makes more power and gets better mileage than a non-hybrid Sierra or a 2011 Ram 1500, and can tow a 3-ton load behind it. Sounds like an ideal truck for urban cowboys working the city by day and dunes on the weekends, right?

The answer depends whether you prefer green in your wallet or within your social circle. The Sierra Hybrid's impressive around-town fuel economy -- typically 6-7 mpg higher than competitive non-hybrids -- is arguably the best reason to buy. Its dual electric motors can motivate the truck up to nearly 30 mph before the 6.0-liter V8 takes over, making stoplight lurches and freeway gridlock largely a gasoline-free activity.

The two-mode hybrid powertrain on the 2011 GMC Sierra 1500 Hybrid is no small engineering triumph. The system juggles the operation of the engine (including cylinder deactivation), two electric motors, and multiple gearsets and clutches. It also coordinates a complex four-speed electrically variable transmission, essentially a combination of a conventional automatic transmission and a continuously variable one (CVT). A nickel-metal hydride battery pack (located underneath the rear bench seat) provides the charge for the electric motors, and a regenerative braking system recharges that battery pack during deceleration.

With the electric motors kicked in, the combined output is 379 horsepower. And to maximize fuel efficiency, the V8 will shut down four cylinders under certain conditions including light-load cruising or when driving downhill.

All of this technology and efficiency comes at a premium, however. The Sierra Hybrid costs significantly more than a comparably equipped gas-only Sierra and doesn't offer much of a boost in highway fuel economy. Even the miserly Sierra XFE is rated just 1 mpg less than the Hybrid's 23 mpg highway rating, while the standard 5.3-liter V8 Sierra still rates a respectable 21 highway mpg. The Hybrid's uneven power delivery and unremarkable towing capacity for its class further limit its appeal.

Considering the premium that the Sierra Hybrid commands -- and that it no longer qualifies for a federal tax credit -- it doesn't strike us as a smart purchase for most buyers. Some green-oriented businesses might like the truck's reduced carbon footprint, and contractors who do a lot of city driving might even recoup the initial price premium after a few years. For most people, though, the 2011 GMC Sierra 1500 Hybrid will likely remain an overpriced curiosity.

The 2011 GMC Sierra 1500 Hybrid is a full-size crew-cab pickup available in a single trim level. The base 3HA configuration comes standard with 18-inch alloy wheels, towing preparation, a soft bed tonneau cover, a 40/20/40-split front bench, keyless entry, full power accessories, dual-zone automatic climate control, a leather-wrapped steering wheel with auxiliary audio controls, cruise control, OnStar, Bluetooth and a six-speaker CD/MP3 stereo with satellite radio.

The 3HB package ups the luxury quotient with foglamps, heated exterior mirrors with integrated turn signals, rear parking sensors, a hard bed tonneau cover, a navigation system with real-time traffic updates, an upgraded Bose audio system with a USB port, rear audio controls, a floor-mounted center console, an auto-dimming rearview mirror, power-adjustable pedals, leather upholstery and power front bucket seats.

A power driver seat is a stand-alone option for the base 3HA. Other options include remote start, a back-up camera and a sunroof.

Available in either two- or four-wheel-drive, the Sierra 1500 Hybrid is powered by a 6.0-liter V8. It's joined by two 60-kilowatt electric motors supplied by a nickel-metal hydride battery pack under the rear seat (warranted for eight years/100,000 miles). On its own, the V8 is rated at 332 hp and 367 pound-feet of torque. GM engineers say that combined output with the electric motors is 379 hp. The four-speed electrically variable transmission is a complex cross between a regular automatic and a CVT.

In Edmunds testing, a 4WD Sierra Hybrid took a leisurely 9.2 seconds to get from zero to 60 mph. By comparison, a conventional 2WD Sierra powered by the 5.3-liter V8 makes the same dash a couple seconds quicker. The Hybrid's maximum tow rating is 6,100 pounds, which is roughly on par with the 4.8-liter and 5.3-liter V8s, but well below the 10,700-pound maximum for the 6.2-liter V8.

EPA fuel economy estimates are 20 mpg city/23 mpg highway and 21 combined. The city is where the Hybrid shines -- most full-size trucks are in the 14-15-mpg range.

The 2011 GMC Sierra 1500 Hybrid comes standard with stability control, antilock disc brakes and full-length side curtain airbags. OnStar is also included.

In Edmunds brake testing, the 4WD Silverado Hybrid came to a stop from 60 mph in 144 feet, below-average performance for trucks of similar heft.

In the government's new, more strenuous 2011 crash testing procedure (the results of which are not comparable to past test results), the Sierra Hybrid received an overall score of four stars (out of five). It got four stars for overall frontal crash protection and five stars for overall side crash protection. The Insurance Institute for Highway Safety, testing the regular Sierra 1500, gave the truck a top score of "Good" for frontal-offset crash protection and a second best score of "Acceptable" for side-impact protection.

The 2011 GMC Sierra 1500 Hybrid doesn't feel as powerful as 6.0 liters and a claimed 379 hp would suggest.

The main culprit is the powertrain's complexity. Floor the Hybrid from a stop and there's a noticeable pause as the truck creeps forward in electric mode, then hurtles away once the gas engine comes online. Acceleration comes in surges between 4,000 and 5,000 rpm. Taller gearing also keeps the V8 largely in a fuel-savings mode, with the electric motors offering less aid as throttle load and vehicle speed increase.

The electric power steering is transparent enough not to highlight itself as in other hybrids. Brake feel, however, alternates between artificial and frustrating. There's a delayed response to actual braking force, then grabby deceleration on engagement.

Inside, the 2011 GMC Sierra 1500 Hybrid is all work truck. Black plastic trim and functional, rudimentary switchgear rule out any pretensions. Still, for the hybrid price premium, we'd like the classy Silverado LTZ dash finery as an option. The rear seat is roomy and comfortable, though the seatback angle is a bit upright.