But I wondered if I could come up with an equivalent $/gallon figure I could tell people what it's actually costing me to drive my Model S.

Here are my assumptions:

Battery: 85KWh (ignoring the 3-5KWH non-bricking margin)

Full battery Range: EPA Rated: 265 miles

MPGe: EPA: 89 mpg (from the window sticker)

Current fuel cost: $4.40/gallon (premium)

Energy cost: $.066 per KWh (I just signed up for a PPA plan with SolarCity for power at 6.6cents/KWH)

Actual A/C power used to fill 85KWH battery: 100KWH (this is just a wild-ass guess, I really don't know how much "wall power" in KWH it takes to fully charge an 85KWH battery. If anyone has a good figure, please let me know)

So if the eMPG is 89, that means the battery stores the equivalent of 2.97 "gallons" of energy.

So to figure the KWH/Gallon, I take the 100 KWH/Battery and divide by 2.97 "gallons"/full battery == 33.58 KWh/gallon.

If power costs me $.066 per KWH, that would be an equivalent of $2.21/"gallon".

That seems high at about only half the cost of premium fuel. Where did I go wrong?