Knock about $200 a month off the Tesla lease for TCO based on Delta between electricity cost in petroleum fuel cost.
Edit: i'm wrong. See below.
Edit 2: In quite a few places, you can get time of day metering, where you pay lower rates for electricity at night.
In Chicago, I pay $0.01/kwh between midnight and 5am; its essentially free to charge my Model S (it's slightly more at my place in Tampa, ~$0.06/kwh at all hours).
The national average cost for gas is $2.67/gallon, Electricity $0.12/kwh. Based entirely on fuel costs, the Model S 85 costs $0.04/mile and the 20 mpg BMW M4 costs $0.13/mile. In order to save $200/month on fuel with the tesla, you'd have to drive 2200 miles a month. In the area I live, where gas is cheaper than average and electricity is almost twice as expensive, that number is 5000 miles/month.
That gas price should be closer to $3.16 at the moment. If we're talking about the luxury car market, it's far more likely the vehicle is going to be consuming premium gasoline.
Edit: i'm wrong. See below.
Edit 2: In quite a few places, you can get time of day metering, where you pay lower rates for electricity at night.
In Chicago, I pay $0.01/kwh between midnight and 5am; its essentially free to charge my Model S (it's slightly more at my place in Tampa, ~$0.06/kwh at all hours).