Are electric cars money savers? Depends where you live.

Saving money on the energy used for every mile traveled is one of the most attractive aspects of electric cars.

Yet varying incentives and other factors mean the savings can vary significantly by state.

So which state's drivers get the quickest return on their electric-car investment?

According to a recent Navigant Research blog post, it's not the green-car mecca of California. It's Indiana.

Hoosier drivers enjoy an average savings of $0.11 per mile over the average gasoline car.

In the state with the lowest savings over gasoline--Hawaii--that number is much lower, at $0.03 per mile.

Taking into account current government incentives, 12,000 miles of annual travel, maintenance-cost reductions, and an average $12,000 premium for plug-in electric cars, Navigant expects Indiana drivers to see a return in four years--twice as quick as Hawaii drivers.

However, the company notes that electric-car returns are significantly affected by localutility rates.

In particular, time-of-use electricity rates--which encourage off-peak usage--could reduce the cost of charging an electric car at home. These rates aren't widely available in the U.S., though.

On an international scale, Navigant found that Norway offers the best return for European drivers, although only relative fuel costs were compared.

Comparing an internal-combustion vehicle with a rated 35 mpg to a plug-in rated at 2.7 miles per kilowatt-hour, it was determined that drivers in Norway save $0.16 per mile, while drivers in Germany only save $0.05.

Norway's extensive government incentives--estimated at around $8,200 per car per year--are likely to save drivers money on more than just fuel.

The country's aggressive incentive program, coupled with relatively short average commuting distances, have made Norway the friendliest place in the world for electric cars.

It's also yielded impressive sales results. Of roughly 2.5 million cars on Norway's roads, already about 1 percent are plug-in electrics.