The Toyota Prius hatchback no longer has a cost advantage over a similar gas model.

If you’re picking a new car, truck or crossover based on the bottom line, you may be in for a surprise, according to a new study. While hybrids tend to deliver better mileage than comparable gasoline-powered vehicles, you may actually wind up spending more in the long run.

Less than one out of four of the 29 hybrids covered by consulting firm Vincentric’s U.S. Hybrid Ownership study actually had lower costs than comparable gas-powered models. Lower pump prices are certainly a factor, but other issues play into the equation – notably including the fact that the fuel efficiency of non-hybrid vehicles has been fast on the rise.

Add the higher cost of hybrid models, said Vincentric President David Wurster, and “Hybrids … may be losing their competitive edge.”

Of those 29 hybrids included in the ownership study, only seven had a clear edge:

It may make more financial sense to own a Toyota Corrolla than a Toyota Prius.

• Audi Q5 Hybrid
• Ford Fusion Hybrid
• Lexus CT 200h
• Lexus ES 300h
• Lincoln MKZ Hybrid
• Toyota Avalon Hybrid
• Toyota Prius C.

Significantly, Vincentric did not find the recently designed Toyota Hatchback to have a cost advantage over a comparable model, such as the Toyota Corolla. And that could further erode already declining demand for what has long been the world’s most popular hybrid-electric vehicle.

(New car sales expected to slide in August. For more, Click Here.)

Including all four Prius-badged models, sales have tumbled 26% since the beginning of the year. Overall, conventional hybrid sales are down, though plug-based vehicles –including plug-in hybrids and pure battery-electric models – are up 7%.

When HEVs first came to market at the beginning of the new millennium, they had a significant advantage over gas models, even though they carried higher prices.

“There are still instances when a hybrid’s cost of ownership savings justify the hybrid price premium,” said Vincentric’s Wurster. But, he stressed, “Buyers should analyze individual models and their own driving patterns to decide whether a hybrid or its gas counterpart is the best choice to save them money in the long run.

Of those hybrid models that did come out on top, The Lexus CT 200h had the biggest advantage in terms of total ownership costs, at $8,728.

(Click Here for details about rising gas prices.)

Of those hybrid models that did come out on top, The Lexus CT 2007 had the biggest advantage in terms of total ownership costs, at $8,728.

The equation could shift again if fuel prices were to go back up to the levels we saw in the U.S. a few years ago, at times nudging $4 a gallon. But few experts anticipate that happening anytime soon.

Meanwhile, automakers have been pushing hard to drive up fuel efficiency on gas-powered products using an array of tricks, including vehicle weight reduction, turbocharging and direct fuel injection, as well as the introduction of new 7-, 8-, 9- and, soon, even 10-speed transmissions.

Nonetheless, many experts believe the market will see even more battery-based vehicles come to showrooms over the next few years, whether in the form of micro-hybrids, hybrids, plug-ins, and pure battery-electric vehicles. The industry may have no option now that federal regulators have indicated they will hold to the 54.5 mpg Corporate Average Fuel Economy standards set to phase in between now and 2025.

(Lincoln nabs top spot in ACSI customer satisfaction survey. Click Here to find out more.)

As for the Vincentric study, it used a five-month weighted average for fuel prices and estimated what it would cost an owner over a five year period driving 15,000 miles annually. Along with the initial purchase price, the study factored in depreciation, fees and taxes, financing, insurance, maintenance, opportunity cost and repairs.