Earth Day, observed on April 22, is a global annual celebration of the environmental movement. The day and its activities date back to 1970.

The environmental push over the past four decades hasn’t skipped big business, which have contributed to concrete advances in new forms of energy, among them wind and solar. Companies have also introduced many new products that run on advanced engine power — power that gives off few if any emissions, especially compared to older, related products that run on fossil fuels.

Click here to see the 10 best green cars

Near the top of the list of products that are using energy more efficiently or using alternative energy are cars. While motor vehicle sales are an important part of the economy, their engines have long contributed to air pollution. Close to 15 million cars and light trucks will be sold this year alone in the U.S. And still the great majority of these continue to be powered by gasoline.

The reasons that people are interested in “green cars” go beyond environmental advantages. Gas prices have been as high as $4 in the last two years. Recently, the price of a gallon of regular gasoline was still above $3.50 nationwide. Despite many improvements in efficiency, gas cars, in many cases, get no better than 25 or 30 MPG. Large pickups and eight-cylinder cars get much worse than that. However, new all-electric engine cars get nearly as high as the equivalent of 100 MPG. That means fuel cost savings savings of hundreds of dollars a year in contrast to an all-gas car.

There have been a number of versions of green cars. The Toyota Prius, the most successful gas-electric hybrid, went on sale in 1997. It was the earliest version of a line of cars that would eventually push Toyota’s all-time hybrid sales above 5 million. Hybrids were a step toward the elimination of cars running exclusively on fossil fuels. The current Prius gets 50 MPG.

The big breakthrough in mileage came with the electric engines and plug-ins. An example is the Prius Plug-In, which gets the equivalent of an estimated 95 MPG in electric mode.

In preparation for Earth Day, research firm Kelley Blue Book put together a list of the Ten Best Green Cars of 2013. Some of these, like the Nissan Leaf, are well known. One is exotic — the Tesla Model S — a hyperfast, sports car. Others are hybrid engine versions of existing model lines like the Toyota Avalon Hybrid. The KBB list is a combination of all-electric and traditional hybrid cars.

On completion of the testing, Jack R. Nerad, executive editorial director and executive market analyst for Kelley Blue Book’s KBB.com, said, “A growing number of eco-conscious drivers are going ‘Green’ when it comes to the new car they choose to drive, and auto manufacturers have primed the pump with the widest array of offerings in the ‘Green Car’ segment than ever before. After driving and testing nearly every new vehicle on the market today, our editors compiled a 10 Best Green Cars list that provides a roadmap for consumers looking to get more miles from each gallon of gasoline or to eliminate gasoline altogether.”

24/7 Wall St. reviewed Kelley Blue Book’s list of the 10 best green cars, which takes into consideration fuel efficiency, value, and quality of hybrid, electric, and plug-in hybrid vehicles. For these 10 cars, we reviewed additional data provided by KBB.com, which included fuel efficiency and 2011 and 2012 sales, we looked at manufacturer’s suggested retail price for the base models, as well as for comparable non-hybrid or electric versions of these models. We also used publicly available data from the Environmental Protection Agency for those fuel efficiency and driving range figures not supplied by Kelley Blue Book. We also considered reviews of these models from groups such as auto data site Edmunds.com.

10. 2013 MKZ Hybrid
> Make: Lincoln
> Price: $35,925
> Combined fuel efficiency: 45 MPG
> 2012 U.S. sales: 6,069

The Lincoln MKZ is a luxury car, with a base price for both the hybrid and non-hybrid models exceeding $35,000. Kelly Blue Book describes the car as possessing the latest cutting-edge technology, including a touch infotainment system, and keyless entry. Edmunds describes the MKZ as similar to the Lexus 300 ES but with slightly better fuel economy and as “sharper to drive.” Lincoln had high hopes for the model, and it has received much press, as well as a $7.4 million Super Bowl ad. However, since the MKZ came out of the gate in December 2012, sales have been very disappointing.

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9. 2013 Avalon Hybrid
> Make: Toyota
> Price: $35,555
> Combined fuel efficiency: 40 MPG
> 2012 U.S. sales: 619

Although the starting price for a Toyota Avalon Hybrid is more than $4,500 greater than the non-Hybrid model, drivers can recover much of their money in savings on gas. According to the EPA, a typical driver would save $5,000 on gas over five years by driving an Avalon Hybrid rather than the average new 2013 car. Drivers of conventional Avalon cars save as well, but the savings are far smaller — just $1,000 over five years. Potential Avalon buyers can select four trims, the XLE, XLE Premium, XLE Touring and Limited. Hybrid versions are available in all but the XLE trim and can cost as much as $41,400 for the XLE Limited.

8. 2013 Fit EV
> Make: Honda
> Price: $37,415
> Combined fuel efficiency: 118 MPG equivalent
> 2012 U.S. sales: 93

Honda launched the Fit EV as its entry in the plug-in electric vehicle market in mid 2012. Originally available only on the West Coast of the U.S., the Fit EV became available in February on the East Coast as well. The plug-in’s fuel economy should appeal to drivers who care about minimizing their impact on the environment. The Fit EV receives the electronic equivalent of 118 MPG combined city and highway, costing an average driver just $500 a year. The Honda Fit EV has a manufacturer’s suggested retail price of $37,415, but according to Honda’s website is available only for lease. For those who would rather not pay for the electric model, a standard Honda Fit costs just $15,425.

7. 2013 Jetta Hybrid
> Make: Volkswagen
> Price: $24,995
> Combined fuel efficiency: 45 MPG
> 2012 U.S. sales: 117

Volkswagen’s long-standing Jetta brand now has, for the first time, a gas-electric model. Wired gave the new 2013 Jetta Hybrid an 8 out of 10, citing as one of the car’s few drawbacks the substantial cost difference — more than $6,000 between the hybrid and the similarly-featured gas-only SE. However, the Hybrid gets a combined 45 MPG, compared to a 5-speed, manual SE’s 28 MPG. In a review of the hybrid, Edmunds applauded the car’s fuel economy as well as its “quick acceleration for a hybrid, spacious interior, and smooth and quiet ride quality.”

6. 2013 C-Max Energi
> Make: Ford
> Price: $32,950
> Combined fuel efficiency: 100 MPG equivalent (electric), 43 MPG (gas)
> 2012 U.S. sales: 2,100

The Energi is the plug-in version of Ford’s C-Max Hybrid. Impressively, the Energi was able to drive 21 miles off just electricity in EPA testing. Adding to that a combined 43 MPG when using a hybrid engine, the C-Max Energi had a driving range of 620 miles. But while the plug-in may save owners money on gas, it may be most-suitable for buyers especially committed to helping the environment because of its relatively high price. The C-Max Hybrid SE costs just more than $25,000, but the MSRP for the Energi is close to $33,000.

5. 2013 Prius Plug-in
> Make: Toyota
> Price: $32,000
> Fuel efficiency: 95 MPG equivalent (electric), 50 MPG (gas)
> 2012 U.S. sales: 12,514

Introduced in Japan in 1997 and in the rest of the world in 2000, the Prius was the first mass-produced hybrid. It has also been by far the most successful. Several different models are now sold under the Prius brand, including the Prius, the Prius C, the Prius V, and the Prius Plug-in. On a full charge, which takes about three hours on a standard home outlet, the Plug-in can travel for roughly 11 miles in electric mode, getting an equivelent of 95 MPG. It then switches to hybrid mode, for which it is rated at a not-too-shabby 50 MPG. Another plus is that in some states the car qualifies for single-occupant carpool lanes.

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4. 2013 Volt
> Make: Chevrolet
> Price: $31,645
> Fuel efficiency: 98 MPG equivalent (electric), 37 MPG (gas)
> 2012 U.S. sales: 22,823

The Chevrolet Volt was introduced to the world in 2008, when then General Motors CEO Rick Wagoner called the car a symbol of the company’s “commitment to the future.” At its release in late 2010, it became one of the first plug-in hybrid cars to hit the road. But not everything has gone smoothly for GM. In 2011, the National Highway Traffic Safety Administration investigated concerns that the Volt’s battery might be susceptible to fire. This may have harmed the car’s reputation despite the investigation closing with the NHTSA determining that the Volt was not at greater risk of a battery fire than other cars. Sales of the Volt were mediocre in 2011 — the car’s first full year of sales — when just under 7,500 units were sold. However, sales tripled in 2012 to more than 22,800 vehicles sold.

3. 2013 Focus Electric
> Make: Ford
> Price: $39,200
> Fuel efficiency: 105 MPG equivalent
> 2012 U.S. sales: 675

The Ford Focus Electric, a fully electric vehicle with a liquid-cooled lithium-ion battery system, gets an estimated equivalent of 105 combined MPG. The cost differential might be a bit much for some buyers, as the standard Focus S sedan has a base price of $16,200, while the Electric’s price tag is just short of $40,000. In a review of the 2013 Electric, Edmunds noted, “the well-rounded, well-built 2013 Ford Focus stands as one of the top choices in an increasingly competitive segment.”

2. 2013 Model S
> Make: Tesla
> Price: $62,400
> Fuel efficiency: 89 MPG equivalent
> 2012 U.S. sales: 2,052

The Tesla Model S is not cheap, with even the lowest-end model costing $62,400 after the $7,500 tax credit buyers receive. However, few cars have been as celebrated as the Model S., which was unanimously voted Motor Trends’ 2013 Car of the Year. But the Model S became subject to controversy when a New York Times reporter noted in his review that the car ran out of battery during his drive. Tesla CEO Elon Musk then accused the reviewer of intentionally trying to flunk the car on his test. The controversy did not prevent Tesla from turning its first profit in its most recent quarter.

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1. 2013 Leaf
> Make: Nissan
> Price: $21,300
> Fuel efficiency: 116 MPG equivalent
> 2012 U.S. sales: 9,512

Since it first debuted in December, 2010, sales of the first zero-emissions have been improving. March was likely the best month for sales in the model’s history. In 2012, sales of the leaf were up by approximately 5%. According to the Detroit News, despite the positive signs, sales growth has not been what Nissan had hoped for, as Nissan hoped to double 2011 sales in 2012. In January company CEO Carlos Ghosn, reiterated long-term sales targets for the leaf, but called recent figures “a disappointment.” According to Edmund’s, while several other 100% electric models have moved into the market, the Leaf remains the most established, and is a safe bet for someone looking to buy an EV model.

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