Electric bikes are all green (colors vary)

"Ride up steep hills without huffing and puffing!" "Hammer at 20 mph without breaking a sweat!" At the recent Interbike trade show in Las Vegas, an explosion of companies touted the Lance Armstrong-like powers of the electric bike -- a pedal-powered bike with an electric motor for extra speed when you need it. Although E-bikes haven't caught on in the United States as they have in Europe and Japan, makers say high gas prices, the obesity crisis, better lithium-ion rechargeable batteries and a wave of green consciousness make them right for the times.

This review includes two styles of electric bikes: "pedal-assist," in which the rider must keep pedaling to actuate the engine, and "throttle," in which the motor can work independently.

-- Roy M. Wallack

Stealth electric bike

Trek 7200+: Electric-assist, hybrid-style 24-speed bike with large-road-bike-size wheels, suspension fork and seat post, rear-hub engine and slide-in battery rack. Bike must be pedaled for the engine to work.

Likes: It looks and feels like a normal bike, until you turn on the quiet, smooth engine with its four power-acceleration settings that accelerate your own pedaling input by 25%, 50%, 100% and 200%. As with all the bikes reviewed here: The more you pedal, the longer the 36-volt lithium-manganese battery lasts. The 7200+ is also "regenerative," meaning that it recharges somewhat with braking and can be set to regenerative mode while on downhills. Claimed mileage for a single full charge, with pedaling, is 40 miles. Recharging is relatively fast: 90% charge in 2 1/2 hours, 100% in 3 1/2 hours. The 6-pound battery slides out of the rack for remote charging. The 7200+ weighs 45 pounds, light as electric bikes go, and is the low end of Trek's three-bike Plus electric line. For commuting, go to the fender- and disc-brake-equipped Valencia+ ($2,500).

Dislikes: None.

Price: $2,309. (800) 313-8735; www.trekbikes.com.

--

Instant Armstrong

Currie Technologies iZip Express: Twenty-six-inch-wheel bike with suspension forks and seat post, a giant in-frame battery, and a powerful 750-watt / 1-horsepower engine in the rear hub.

Likes: The giant motor leaves you feeling supercharged. Working moderately hard (not all-out), I went 25 mph up a long hill in a head wind. The 36-volt lithium-ion battery has five levels of assist; claimed range on a full charge is 31 miles on high-power mode, 45 miles on standard mode, and more than 50 on economy mode. Top speed on flat ground with minimal rider pedaling is 20 mph. Currie Technologies is one of the country's biggest E-bike distributors. This is its highest-end bike.