It's just as hard picking the 10 best green cars from Detroit's North American International Auto Show as it is picking the 10 best cars overall, but for different reasons. It's hard to keep the 10-best-greenies list down to 10; it's almost as hard to get the 10-best other cars list up to 10. Toyota and Lexus could fill out much of the green cars list on their own, with the 2010 Prius and its astounding 50 mpg fuel economy; the HS 250h, a Prius by Lexus ("don't call it a Lexus Prius," the Lexus people moan); and Toyota's battery-only concept car, the TF-EV. Here's my top 10 green cars from Detroit's 2009 auto show, rated by likely impact, including the odds of actually coming to production.

1. Toyota Prius Hybrid

Toyota filed for more than 1,000 patents with the third-generation Prius arriving late this spring. It's roomier inside with a revised roofline, yet the shape is unmistakably Prius. Most of the drivetrain parts are smaller, lighter, and more efficient. Combine that with very low wind resistance and you get 50 mpg combined city/highway mileage. A replacement was long overdue since the current model dates to 2004.

2. Honda Insight Hybrid

The oddly shaped, two-seat first-generation Insight from 1999 didn't sells squat. The 2010 model looks a lot like the Toyota Prius (but then a long roofline is one way to improve aerodynamics) and now is a four-door, five-passenger hatchback that will likely undercut Prius by several thousand dollars in price. Honda says it will be cheaper than a Honda Civic ($24,000), but then so is the outgoing 2009 Prius. It's a parallel or mild hybrid, meaning the electric motor only runs in conjunction with the gasoline engine. That's not as sexy and possibly not as magnetic as a strong hybrid, such as Prius, that can run on battery power alone. Honda estimates 40 mpg city, 43 mpg highway, 41 mpg combined. That sounds a lot worse than the 50 mpg Prius will get, but mpg comparisons aren't linear (11 vs. 20 mpg is different from 41 vs. 50) and in 12,000 miles of driving amounts to an extra 53 gallons of gas, or just under $100 at today's prices. It's on sale in April.

3. BYD F6 DM

BYD stands for Build Your Dreams and chairman Wang Chuanfu's dream is to be the world's largest automaker by 2025. He might be blowing smoke, but if so, then one person BYD fooled is Warren Buffet, who has a stake. Last year the Detroit show relegated the Chinese to an outside concourse and for press days only; this year BYD and Brilliance Automotive are on the inside (albeit way in back). BYD says it will have the hybrid F6 DM to market by 2011. American automakers laughed at German cars, Germans laughed at the Japanese, the Japanese laughed at the Koreans ... maybe we shouldn't be making light of the first steps of the Chinese into the world auto market.

4. Lexus HS 250h

The first hybrid-only Lexus model will use existing or just-developed Toyota/Lexus parts including a four-cylinder hybrid engine, recently introduced technology such as the SafetyConnect telematics package, and typical Lexus fit and finish inside and out. It will be bigger than a Prius (but smaller than the mid-size Lexus ES) and likely won't match the new Prius' 50 mpg; Lexus only says it will do better than 33 mpg when it ships in late summer. Remember, this is not a Lexus Prius. It only seems that way. And not to poke further fun, but HS stands for hybrid sedan, while every Lexus hybrid has a lowercase h at the end already.

5. Mercedes-Benz BlueZero Concepts (Battery, Fuel Cell, Plug-In Hybrid)

This four-passenger minicar concept has three configurations, all with plenty of crash safety and miminal cockpit intrusions from the electric motors: The E-Cell battery-only model gets 124 miles (200 km) before recharging. The F-Cell uses a fuel cell for additional electricity and runs for 248 miles (400 km). The BlueZero E-Cell Plus adds a small combustion engine for a range 372 miles (600 km), or 62 miles (100 km) on battery alone.

6. BMW X6 Concept Hybrid

This will be BMW's first dual-mode hybrid (runs on gas, runs on batteries, runs on both) to market based on the joint work of BMW, DaimlerChysler (done before the divorce), and GM. Look for it late this year. BMW also showcased the BMW 7 Series Concept Hybrid with a parallel powertrain, meaning you get electric motor boost only when the gas engine is running.

7. Fisker Karma S hybrid

The Karma Sunset (that's the S in the name) is a plug-in hybrid two-seat, hardtop convertible. Plug-in means you run up to 50 miles on two powerful electric motors, then switch to a GM 2-liter turbo gasoline engine for up to 300 miles (more if you fuel up), then recharge the batteries when you're back home. Fisker claims 0-60 mph in 5.8 seconds. Deliveries would be in 2011. Fisker claims 1,300 pre-orders for the original Karma plug-in hybrid due to ship later this year from a factory in Finland now building Porsches. Fisker says it can build 15,000 vehicles a year (each costing just under $100,000), which would be pretty good for a startup.

8. Volkswagen BlueSport Concept

VW's gorgeous little two-seater convertible would have a 180-hp clean turbodiesel engine and get 55 mpg. But: VW has no existing platform for such a vehicle and it would be costly to create one for a market (Mazda MX-5, Pontiac Solstice, Saturn Sky and other low-cost roadsters) that's only about 30,000 a year (in the U.S).

9. Cadillac Converj Concept

Like the Chevrolet Volt, the Converj would go 40 miles on batteries, then you'd recharge, or keep running for 500 miles on the small gasoline engine. Where Volt is slated for production late in 2010, Converj plans are sketchier, and some think it was cobbled together to look good to visiting Congressman who want to know where the bailout money is going. (Answer: Mostly to bankers in New York, by an order of magnitude.) The body is the same as Cadillac used for a 550-hp gas-engage CTS Coupe prototype that was never unveiled last fall on account of it being the wrong car at the wrong time. Kudos to Jerry Garrett of the New York Times for the catchy name, Coupe de Volt.

10. Chrysler 200C EV Concept

Strapped for cash, Chrysler showed a less-far-along extended-range electric than the Chevrolet Volt. But the concept is similar: battery power for 30 or 40 miles, gasoline power for several hundred more, and hope you can stay in business long enough to get the sucker to market. The UConnect telematics feature lets you track the location of buddy vehicles you've friended (or parents could know where the teenager is). The body shell could be the replacement for now aging Chrysler 300 design and would likely show up first as a gasoline, then hybrid, and then as an extended range electric.