Yesterday we listed the nominees for Green Car Reports' Best Car To Buy 2014 award: two battery-electric vehicles, one hybrid, one diesel, and one very fuel-efficient gasoline car.

But what do our nominees say about the state of green-car design this year?

Overall, they highlight four trends to keep in mind as you shop for your next car.

Green Car Reports' Best Car To Buy 2014 award

Green Car Reports' Best Car To Buy 2014 award

(1) Electric cars are getting more efficient.

The 2014 Chevrolet Spark EV has the highest EPA combined efficiency rating of any plug-in electric car sold in the U.S. today: 119 MPGe, or miles-per-gallon-equivalent.

(MPGe is a rating that looks at how far an electric car can travel on the amount of energy contained in 1 gallon of gasoline.)

By comparison, the Nissan Leaf is at 115 MPGe combined, the Chevy Volt gets 98 MPGe in all-electric mode, and the Tesla Model S (85-kWh version) is rated at 89 MPGe.

MORE: 2014 BMW i3: First Drive Of BMW's Radical New Electric Car

We don't yet have EPA ratings for the 2014 BMW i3, but it's possible it could come in that high as well.

Its carbon-fiber reinforced plastic body shell is far lighter than it would have been if made of steel, and BMW says the i3 delivered 4.4 miles per kilowatt-hour in European testing.

2014 Honda Accord Hybrid

2014 Honda Accord Hybrid

(2) Hybrids will continue to gain ground.

The 2014 Honda Accord Hybrid is a new entry for the Japanese carmaker that was the world's second hybrid producer, way back in 1999.

It will compete directly with strong and established entrants in the mid-size sedan segment: hybrid versions of the Ford Fusion, Hyundai Sonata, Kia Optima, and Toyota Camry (plus the hatchback Toyota Prius).

A few years ago, in the face of Toyota outselling it in hybrids about five-to-one, Honda acknowledged that its Integrated Motor Assist (IMA) mild-hybrid system wasn't enough.

It developed both the Accord Hybrid's two-motor system and a more powerful single-motor system that will launch in future small cars to replace IMA.

The message: More and better hybrids are coming, from more makers--even including European brands like Audi, BMW, Mercedes-Benz, and Volkswagen (although they'd really rather sell you diesels instead).

Some analysts say hybrids will make up as much as 10 percent of global vehicle production by 2020.

2014 Chevrolet Cruze Diesel

2014 Chevrolet Cruze Diesel

(3) Diesels are coming, but they'll be pricey.

The 2014 Chevrolet Cruze Diesel has attracted a lot of interest, and justifiably so: It's the first diesel passenger car from General Motors since 1986.

And its 2.0-liter turbodiesel four-cylinder engine is an adaptation of one it's used in Europe for many years, where diesels take roughly half the passenger-car market.

MORE: 2014 Chevrolet Cruze Diesel: First Drive

The 2014 Jeep Grand Cherokee EcoDiesel is the other diesel passenger vehicle that's expected to sell in substantial numbers this year. But both are expensive.

The 2014 Cruze Diesel carries a base price of $25,810, whereas the least pricey gasoline Cruze model is just $18,095. (Both prices include the mandatory $825 delivery fee.)

And it's the same for the Jeep: The EcoDiesel adds $4,500 to the price of the higher-end Grand Cherokee models, for an effective base price of $40,295, against the base gasoline Grand Cherokee at just $28,795. (These prices do not include the destination fee.)

In a way, it's similar to the tactic used by hybrid makers (and criticized by consumer advocates), in which the expensive powertrain technology is only offered on high-end models to recoup some of the maker's cost.

2014 Mazda 3 sedan leaked

2014 Mazda 3 sedan leaked

(4) Plain old gasoline engines can get a lot more efficient.

Finally, while electric cars, hybrids, and other advanced technologies get a lot of attention, the plain old gasoline engine has a lot of life left it in--and a whole lot more gas mileage too.

The race-trained engineers in Mazda's powertrain group have worked hard to wring every last efficiency out of its new SkyActiv line of engines, both gas and diesel, and transmissions.

And it works: We did much better than EPA ratings on two SkyActiv-engined Mazdas we tested last year. (In a different vein, the 2014 Mitsubishi Mirage did the same.)

To follow details of this year's nominees, along with details of the previous years' awards, see our Best Car To Buy page.


Follow GreenCarReports on Facebook, Twitter, and Google+.