It can be hard to work out which cars the 2012 Tesla Model S electric sport sedan competes with.

Would it be largest German luxury sedans, which it roughly matches in price with the longest (265-mile) range and the introductory limited-edition Signature Series models?

If so, those would be the Mercedes-Benz S Class and the BMW 7-Series full-size luxury sedans.

Or, as some readers suggest, the next level down, perhaps the Tesla Model S more properly competes with the BMW 5-Series and Audi A6?

(We doubt that many Model S reservation holders cross-shopped Tesla's electric sedan against the Nissan Leaf, the highest-selling battery-electric vehicle in the U.S.)

One way to compare cars--the way U.S. regulatory agencies do it--is to look at interior space and cargo volume. But even there, there's been some dispute.

When the EPA issued its 265-mile range and 89-MPGe efficiency ratings for the 2012 Model S, the agency gave the electric sedan's interior volume as 94 cubic feet and cargo space at 26 cubic feet.

The comparable figures for the Nissan Leaf are 90 cu ft and 24 cu ft (with the rear seat folded down) or 14.5 cu ft (with the seat up).

This led to a discussion with Tesla Motors [NSDQ:TSLA] communications staff, ending some days later in the final specifications sheet for the 2012 Model S.

That shows 95.1 cubic feet of interior volume, plus 58.1 cu ft of rear load-bay volume (with the seat down) or 26.3 cu ft (with the seat up).

But there's a kicker: the so-called "frunk," or front trunk, which offers an additional 5.3 cu ft of load space where a conventional car would have its engine and transmission.

(That's just 1.6 cu ft less than the entire 6.9-cubic-foot trunk of the sleek and sexy 2012 Fisker Karma, by the way.)

2012 Tesla Model S beta vehicle, Fremont, CA, October 2011

2012 Tesla Model S beta vehicle, Fremont, CA, October 2011

So, by Tesla's numbers, the maximum total cargo volume in a Model S with both seats remaining up (and without the optional cargo-bay jump-seats) is 31.6 cubic feet.

Tesla communications manager Shanna Hendriks notes that the EPA relies on volume figures provided by automakers.

The company's initial submissions to the agency on Model S volume didn't include the "frunk," but the company has since corrected this.

And indeed, the EPA has since updated the numbers for the 2012 Tesla Model S on the website, which now shows 31 cu ft of cargo volume.

And now you know.


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