Calculator runs cost numbers for plug-in vehicles

Automakers this week are showing off all manner of fuel-efficient concept cars at the Frankfurt auto show in Germany. But, in general, the majority of people are reluctant to pay a big premium for the last green auto technology.

Think tank the Rocky Mountain Institute has launched an online calculator to figure what higher up-front cost brings you in terms of savings and environmental benefits. It's part of the group's Project Get Ready to prepare communities for plug-in electric vehicles.

The price premium of greener cars is an important issue as the auto industry readies many plug-ins designed for everyday use. These first-generation cars, such as the all-electric Nissan Leaf or Chevy Volt, will have a bigger price tag because they will carry a bigger--and pricier--battery than today's hybrids. But owning an electric car "fueled" by electricity is typically going to be cheaper per mile than gasoline.

The calculator is structured so that you can compare the lifetime costs of two cars, giving you the ability to input a number of variables, such as cost of gas, lease versus buy, and how many miles you drive. It lets you take your best guess at gas prices--today it's at $2.61 per gallon--and assumes electricity costs of 9 cents per kilowatt-hour, though these days that price is more like 11 cents per kilowatt-hour, according to the U.S. Energy Information Administration. Six years is the default number of years to own a car because it's a national average.

Running through a few examples shows upcoming electric cars are indeed cheaper to own, but more expensive upfront. Keep in mind that the calculator includes both available models as well as a number of cars, notably plug-in electrics, that are not yet available.

For example, the driver of a Chevy Volt, which runs on an electric motor and has a gasoline engine for distances longer than 40 miles, will spend almost $2,500 less on fuel than a hybrid Honda Insight over six years. Does that justify a sticker price that's higher by more than $13,000 in your mind? Now you can decide.

The all-electric cars, such as the Nissan Leaf or the BYD e6, come off as most competitive when it comes to total cost of ownership. On the other hand, you're limited in range to about 80 or 100 miles for these first-generation battery electric cars.

After 10 years, the driver of a Leaf saves $7,684 on fuel compared to a Nissan Altima, offsetting the $7,000 more you need to pay to purchase a Leaf. Play around with the calculator a little more and you see that $4 per gallon gas means that $7,000 premium is offset in a bit over 5 years.

It's useful for comparing hybrids versus gasoline-only cars as well. The hybrid version of the Honda Civic saves you $1,616 over six years but costs $6,752 more. It's cheaper to own right out of the gate when gas prices are around $6 per gallon, according to the calculator.

If you're thinking about converting a Prius to a plug-in version, you're going to pay for it. The calculator estimates it will cost $19,165 more and save just over $2,011 in fuel over 6 years. Meanwhile, a plug-in Ford Escape is cheaper to own than a hybrid Ford Escape after 10 years with today's gas prices, and after 7 years if gas costs $3.50.

Cost isn't everything to everybody, of course. With millions of hybrids sold already, people are clearly willing to pay more for better mileage for environmental or energy security reasons. This calculator has additional metrics on amounts of oil used and carbon dioxide equivalent emissions between two cars, which is handy.

On the whole, the calculator shows that a number of variables play into the buying equation--beyond things like brand, status, and a car's looks. Even though many of the cars listed aren't yet available and there are more comprehensive comparison sites, it's a useful place to look.

The industry hasn't decided on the best way to compare emerging technology to today's gasoline cars--will it be miles per gallon equivalent, range, or cost per mile? As electric vehicles of various guises come to market, consumers will need to grapple with mileage claims that, most likely, will be tricky to sort through.