As we approach St. Patrick’s Day, we turn our attention to everything green.

Green hats. Green shirts. Green beer. Green Cars.

Well, not that kind of green car. We’re talking about environmentally friendly gas-sippers that will save you money every time you’re at the pump (if you have to fill up at all).

With more categories of green cars than ever to choose from, we’ve put together a list of the most prominent to help you understand your choices.

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Fuel-efficient gas models

For years, Detroit struggled to produce fuel-efficient vehicles. Heavy trucks (think Hummer) and huge family station wagons resulted in gas-guzzlers dominating the roads.

But, the rising cost of oil combined with the emergence of concern for the environment prompted action. By 2016, American-made cars will have a mandated fuel efficiency of 34.5 mpg on average. This rises to 54.5 mpg by 2025.

The emergence of hybrid and electric vehicles will go a long way to meeting these requirements. But, gas powered vehicles are also becoming more efficient than their predecessors.

Honda’s CR-Z and Scion’s iQ lead the way in this category. They average a combined fuel economy (highway and city driving) of 37 mpg.

If you need something a little sportier or larger, the Audi A3 diesel, Ford Fiesta SFE and Honda Fit wagon come in just behind, averaging 36 mpg.

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Gas-electric hybrids

In 2000, the Toyota Prius launched the hybrid electric vehicle (HEV) revolution. With a combination electric/internal combustion engine, it could run on batteries when needed, but still have the peace of mind of a combustion engine for power and travel distance.

Last year, over 452,000 HEVs were sold in the United States. Almost all manufacturers have produced HEVs, including luxury brands such as BMW, Lexus and Mercedes. In fact, HEVs come in all model lines, from compact to the Chevy Tahoe.

The Prius still leads this pack when it comes to fuel efficiency, averaging a combined 50 mpg.

Plug-in hybrids

A more advanced version of its HEV cousins, a plug-in hybrid electric vehicle (PHEV) can recharge its batteries by plugging in to a conventional power outlet. These cars can run exclusively on electricity, but still retain a combustion engine in case of full battery discharge.

The Chevrolet Volt is one of the most popular PHEV models. Toyota has released a plug-in Prius as well. They both get approximately 60 mpg. And if you’re searching for a more luxurious plug-in, Cadillac just released the ELR in 2014.plug-in hybrid

All electric

Once considered a dream, the electric car is now a reality. With no internal combustion engine, these vehicles are propelled by battery power only. If you need to “fill up,” all you need to do is plug the car into an electrical outlet.

What keeps many people from purchasing an all-electric vehicle is the concern over range and power. At the moment, most all electric vehicles have a range of between 50-100 miles. This means that you can drive that many miles before having to plug-in and recharge your car.

However, the Tesla Roadster and Model S boast both significantly longer ranges and extreme power. Their range is between 244-300 miles/charge. And, the new dual-motor Model S can go from 0-60 mph in just 3.2 seconds. That’s comparable to a Ferrari, McLaren or Lamborghini.

Fuel cell vehicles

Fuel cell vehicles (FCVs) might be the next big thing in green cars. A step beyond all-electrics, FCVs rely on hydrogen to power their engines. This produces emissions of only water and air.

Toyota is about to release the first mass-produced FCV with the Mirai. What still remains to be seen is how quickly the fueling infrastructure of hydrogen stations can be built up to support these futuristic vehicles.