I’ve had my Model S for almost two weeks now. During that time, I’ve driven 396 miles, using a total of 128 kWh for an average energy usage of about 324 Wh/mi, which, I gather from perusing these forums, represents average energy usage. I thought I would use these preliminary figures to do some back of the envelope calculations as to how efficient the Model S is in terms of energy usage as well as its cost of ownership.
My garage circuit has a dedicated account with a time of use (TOU) plan allowing me to program the car to be charged during “super off peak hours” in which my energy cost is 1.3063 cents/kWh. I understand from previous posts that there is energy loss between the wall circuit and the car, so I have used a 15% multiplier to calculate my actual energy usage based upon previous suggestions.
Thus, in order to drive 396 miles, I’ve spent $1.92 on energy (= 128 kWh * 0.013063 $/kWh * 1.15).
Another way to think of this, rather than the miles per gallon (MPG) we’re used to thinking of when we discuss fuel efficiency in regular cars, is that I’m getting 206 miles per dollar ( = 396 mi/$1.92). By comparison, my Prius (which I gave to my daughter when I bought the Model S), gets 50 mpg, and, at $3.50/gallon, I’m getting an actual economy of 14.2 MP$.
Obviously, depending upon where you live, and what kind of energy plan you have, this will vary greatly. It also matters, of course, HOW your energy is generated: coal, nuclear, natural gas, hydroelectric, wind, solar, etc.
I typically drive about 12,000 miles/year, so if I’m getting 206 MP$, my yearly energy usage is just over 58 dollars.
Let’s assume I keep the car three years and drive 36000 miles. My energy cost for the three years will be roughly $175. My real cost of owning the car, then, will largely be determined by depreciation. My sticker price prior to taxes was about $76K. I spent another $2K to rewire the garage. After sales tax ($5K in Georgia), and tax rebates ($7,500 fed and $5000 state), my “cost” to buy the Tesla was $67,500. Elon guarantees resale value of 50% at three years, plus a nominal amount of resale value for options. Thus my depreciation for three years of ownership should be about $28K. So the real expense of owning a Tesla, in my situation, is not the fuel but rather the depreciation, which, at 12K driving miles per year, works out to about 78 cents per mile of driving. These back of the envelope calculations, of course, ignore other expenses such as insurance, maintenance (minimal with the Tesla), etc.
All of this is well and good, though, since most of us bought the Model S not for fuel economy but because we’re early adopters, can afford it, and tend to be fascinated by new technology. But for this technology to gain a foothold in the marketplace with a significant share, it will need to be cost effective without tax breaks. I would be curious to hear what the operating expenses are for other Model S owners in other parts of the country.
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