Cheap electricity and reduced maintenance needs make most electric cars cheaper to operate per mile than internal-combustion models, but perhaps that doesn't take things far enough.

There seems be an even better way to save money on transportation in some areas: Get rid of the car entirely.

Car-sharing and ride-sharing services in urban areas are proving more convenient for some people than public transportation, but is it really cheaper to ride than drive?

One San Francisco resident decided to find out. In a personal blog post, Sam Altman compared the cost of driving his Tesla Roadster to getting rides using UberX.

Golden Gate Bridge, connecting San Francisco and Marin County, California

Assuming 6,000 miles traveled per year, he determined that driving the electric carcosts $13,600, while uberX came in at $12,000.

Altman estimated an average cost of $2.00 per mile for uberX, the only real cost associated with the ridesharing service.

Car ownership is a bit more complicated, of course.

While he calculated charging costs at 25 cents per kilowatt-hour, or roughly double the average national rate, they still came to only around $10 for a full charge giving him 150 miles or more.

Altman also said he spends $3,600 per year to park his Roadster, plus $1,200 for insurance and $3,500 for maintenance.

But, crucially, he did not factor in the purchase price of his now-discontinued Tesla Roadster.

With a base price of over $100,000, the Roadster cost significantly more than the average car when new, and there are many far less pricey plug-in electric alternatives on the market today, five years later.

He did, however, factor in $5,000 a year in depreciation out of concern that the battery pack would degrade over time.

All of these factors made uberX the less-expensive choice in this situation, assuming the service doesn't raise its rates.

Of course, the availability of ridesharing or public transportation in the first place, along with local electricity costs, and the particular requirements of different cars will change the outcome for other drivers.

Owners may also want to consider possible environmental effects.

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It may be cheaper, but habitually leaving an electric car at home to hitch rides in an internal-combustion one may increase a traveler's carbon footprint over time.

[hat tip: Brian Henderson]