A Motor Trend review recently that looked at the realistic range obtainable in a Tesla. A 528i chase car allowed for somewhat of a real world but still an apples to oranges comparison. The trip was 238 miles which was about the full extent of the Tesla’s juice—i.e., 78.2 kWh.
Unfortunately, MT erroneously compared the Tesla’s performance to the gallons of fuel used by the 528i on the trip —i.e., MT compared the 528’s mpg to the amount of energy in 2.32 gallons for the Tesla. Needless to say, iMT did not bother to consider the amount of energy that is required in the real world to generate the 78.2 kWh of electricity needed to charge the Tesla’s batteries.
For example, a diesel generator can produce around 3.2 kWh /liter of fuel. So, the 78.2 kWh that the Tesla used in the MT comparo to go 238 miles would have required 24.4375L or 6.46 gallons of diesel fuel to produce. Losses to transmit electricity over the grid is 5-7% which when factored in to the calculation results in 6.78 to 6.91 gallons of diesel for the Tesla’s 238 miles… not, 2.32 gallons.
The BMW 528i, managed 30.1 mpg; however, it uses gasoline not diesel so that requires an adjustment. But, using the 6.78-6.91 gallons of gas (not diesel fuel) the 528i would have gone about 204 to 207 (not 238 so a little less); however, if the 528i had been a diesel it would have gone a lot further on the same amount of diesel fuel –e.g., instead of the 528i’s 30.1 mpg, the Mercedes E250 BlueTEC comes in at 28 city and 42 highway. The combined mpg is somewhere in-between.
In one E250 BTC review the results were as follows: “by the end of our five days with the E250 BlueTec, we’d averaged an indicated 40.6-mpg over 595 miles. At that time, the instrument display was still showing a remaining range of 235 miles—so from the 21.1-gallon tank a total driving range of more than 800 miles would be within a real-world (non-hypermiling) reality.”
Accordingly, using the 40.6 combined mpg of the E250 BTC puts the mileage at 275 – 277 miles (not just 238 miles) on 6.78 – 6.91 gallons of diesel fuel (and, the E could be driven over 500 additional miles without having to refuel).
