Hidden within a previous post on “How Green is Your Tesla” was a discussion of fuel costs. But with gas pricing falling, I thought fuel costs deserved another look. Attached is a handy spreadsheet that calculates how many miles per gallon your gas powered car has to get for fuel costs to be less than for a Tesla Model S 85. The calculation is done assuming that electricity costs either 25 cents or 35 cents per kilowatt hour. Those are the second and third tier rates charged by Southern California Edison in the Los Angeles area. You can plug in your own rate, but remember you want a marginal rate after taking account of your normal home usage. The marginal rate is more likely priced at a higher tier. The spreadsheet also takes account of the fact that the actual Tesla range is on the order of 67% of the stated range as documented in the previous post.

As the spreadsheet shows, given a cost for gas of $4.15 per gallon (the currrent mid-grade rate in Los Angeles) , the breakeven mileage is 34.0 mpg at the 25 cent electric rate and 24.3 mpg at the 35 cent rate. The bottom line is there may be a lot of reason for choosing an electric car but saving on fuel costs is not likely to be one of them, at least at current prices.

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