Gas prices remain volatile, but even so, no one expects prices below $3 per gallon ever again, and many parts of the country consistently see prices near or above $4. As much as ever, shoppers need to know how effectively hybrids deliver efficiency for your dollar — if they do at all.

To determine if a hybrid’s added expense is worth the cash, we devised an efficiency-cost rating to reflect efficiency bang for your overall buck.

It’s simply the combined city/highway mpg divided by the base price (MSRP plus destination charge). We then multiply that number by 1,000. This formula can be applied to any type of vehicle, hybrid or not. A high mpg rating and low price provide a high efficiency-cost rating. A higher score is the better score.

We don’t account for equipment levels, quality judgments, cost of ownership or any variances from EPA mileage estimates. The goal here is to pay the least for the most mileage, barring all other considerations.

Subcompact Cars

2013 Toyota Prius c
Price: $19,875
Gas mileage (city/highway; combined mpg): 53/46; 50
Efficiency-cost rating: 2.52

With an efficiency-cost rating of 2.52, the subcompact 2013 Toyota Prius c is still the top-rated hybrid ahead of the compact Honda Insight (2.17). It’s also ahead of the regular Toyota Prius, which tops the midsize-car category.

Compact Cars

2013 Honda Insight
Price: $19,390
Gas mileage (city/highway; combined mpg): 41/44; 42
Efficiency-cost rating: 2.17

The 2013 Honda Insight remains the best bang for your buck in this size class with an efficiency-cost rating of 2.17. It also soundly beats its stablemate, the Honda Civic Hybrid, rated at 1.75.

Midsize Cars

2013 Toyota Prius
Price: $24,995
Gas mileage (city/highway; combined mpg): 51/48; 50
Efficiency-cost rating: 2.00

With an efficiency-cost rating of 2.00, the 2013 Toyota Prius is the best of the midsize cars and third overall – quite an accomplishment considering its interior volume and thrifty fuel numbers. If you value roominess along with results, the Prius remains the king of the hybrids.

2013 Ford Fusion Hybrid
Price: $27,995
Gas mileage (city/highway; combined mpg): 47/47; 47
Efficiency-cost rating: 1.68

Those who prefer sedans will see that efficiency-cost ratings drop considerably. With its updates, the 2013 Ford Fusion Hybrid tops the growing midsize-sedan hybrid class. The Fusion Hybrid has come under high-profile scrutiny after many owners claimed they weren’t achieving, or even nearing, the EPA-estimated mileage. If this concerns you, consider the next-highest-rated 2013 Toyota Camry Hybrid, which held this spot last year. Its combined mileage estimate is a less impressive 41 mpg, but its base price is lower at $26,935, giving it a 1.52 rating.

Full-Size Cars

2013 Ford C-Max Hybrid
Price: $25,995
Gas mileage (city/highway; combined mpg): 47/47; 47
Efficiency-cost rating: 1.81

While there are no affordably priced full-size hybrid sedans, there are now reasonably priced hatchbacks larger than the Prius, including Toyota’s own Prius v. However, this is the one category out of three where the Prius model doesn’t rule. Thanks to its higher mileage and lower price, the 2013 Ford C-Max Hybrid leads. Like the Fusion Hybrid, the C-Max Hybrid has accrued a disproportionate number of complaints about its true mileage performance. If this concerns you, the Prius v has a lower, but still respectable, 1.53 efficiency-cost rating.

Midsize SUV/Crossover

2013 Toyota Highlander Hybrid
Price: $41,015
Gas mileage (city/highway; combined mpg): 28/28; 28
Efficiency-cost rating: 0.68

The Highlander Hybrid remains the highest-rated SUV of any size, partly because Ford’s Escape no longer comes as a hybrid. The 2013 Highlander Hybrid’s ECR is actually lower (worse) than that of the most affordable non-hybrid Highlander (0.74), but that’s because the hybrid comes only with all-wheel drive. The gas-only Highlander with all-wheel drive costs more and thus has a worse ECR than the hybrid version: 0.58.

Full-Size SUV/Crossover

2013 Chevrolet Tahoe Hybrid
Price: $54,040
Gas mileage (city/highway; combined mpg): 20/23; 21
Efficiency-cost rating: 0.39

For people who need the capabilities a full-size SUV brings, the Chevrolet Tahoe Hybrid is the most cost-effective hybrid of its size. The Tahoe Hybrid can tow up to 6,200 pounds with rear-wheel drive, so for those who take their boats to pristine lands, this is the greenest option. Or is it? If you compare features, the Tahoe Hybrid might improve on a high-priced version of the gas-only Tahoe, but with a starting price more than $13,000 less, the base Tahoe has an efficiency-cost rating of 0.42 — better than the hybrid.

Pickup Truck

2013 Chevrolet Silverado Hybrid
Price: $42,130
Gas mileage (city/highway; combined mpg): 20/23; 21
Efficiency-cost rating: 0.50

As the more affordable version versus its sibling, the GMC Sierra Hybrid, the 2013 Chevrolet Silverado takes the top spot with a modest efficiency-cost rating of 0.50. If you insist on a Chevy pickup — or want a hybrid for hybrid’s sake — the Silverado Hybrid is for you. But you can do better: The high-efficiency version of the 2013 Ram 1500, called the HFE, has a 0.71 efficiency-cost rating. It’s not the cheapest 1500 truck, at $29,505, and its towing capacity tops out at 4,750 pounds, but it’s much cheaper than the Silverado Hybrid and has the same combined mileage estimate of 21 mpg. The Silverado Hybrid tows up to 6,100 pounds, though.

Luxury SUV

2013 Lexus RX 450h
Price: $47,205
Gas mileage (city/highway; combined mpg): 32/28; 30
Efficiency-cost rating: 0.64

If you want a hybrid and a lush SUV, there are a few choices that serve that dual purpose well, but the Lexus RX 450h’s efficiency-cost rating outperforms the rest. Even with all-wheel drive, the RX 450h’s ECR of 0.60 outdoes the Volkswagen Touareg Hybrid at 0.33 and Porsche Cayenne Hybrid at 0.30, both of which come standard with all-wheel drive … and $60,000-plus price tags.

Luxury Cars

2013 Acura ILX Hybrid
Price: $29,795
Gas mileage (city/highway; combined mpg): 39/38; 38
Efficiency-cost rating: 1.28

Many folks remain baffled by the very notion of a hybrid luxury car, but there’s proven demand. More of these seeming contradictions join the market all the time, including some truly efficient ones. Some would argue the compact Acura ILX Hybrid isn’t exceptionally luxurious, but it carries the highest efficiency-cost rating of any luxury vehicle at 1.28. This edges out the 2013 Lexus CT 200h, which is rated 1.27. Despite a 42 mpg combined EPA estimate, the Lexus is priced higher.

2013 Lexus ES 300h
Price: $40,145
Gas mileage (city/highway; combined mpg): 40/39; 40
Efficiency-cost rating: 1.00

With an efficiency-cost rating of 1.00, the midsize 2013 Lexus ES 300h sedan blasts past the Infiniti M35h, which held this position last year. With a higher price and lower EPA-estimated mileage, the M35h’s ECR is 0.52. Its main selling point for driving enthusiasts is its rear-wheel drive; the front-drive Lexus is less sporty.

2013 BMW ActiveHybrid 740 Li
Price: $85,195
Gas mileage (city/highway; combined mpg): 22/30; 25
Efficiency-cost rating: 0.29

With an EPA-estimated 25 combined mpg, which is impressive for a large, long car, the 2013 BMW ActiveHybrid 740 Li has an efficiency-cost rating of 0.29. It’s low for any hybrid, but it’s the best of the full-size luxury sedans, beating the Porsche Panamera S Hybrid (0.26), Mercedes-Benz S400 Hybrid (0.23) and preposterous Lexus LS 600h (0.17). However, the gas-only BMW 740’s ECR is better at 0.30 with an estimated 22 mpg combined for $74,495. The Mercedes S400 is the only hybrid luxury car that beats its gas-only version, by a slim 0.03 in efficiency-cost.

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