I agree with those who consider MPGe as being not useful. The energy content of a gallon of gasoline tells little about how far it will take an ICE car since gasoline mileage varies. So does electrical mileage in EVs: the LEAF is more efficient than a Tesla Model S, for example.
Nubo said:
...MPGe gives the first answer. The second answer is best given in terms of cents per mile. For LEAF you need to know the cost you are paying for a kWH of electricity, factor in charging losses, etc..
What I think you're really looking for is:
3 - How far will the LEAF go for the same amount of money it costs to buy a gallon of gasoline. For that answer you first need to know and understand both 1 and 2. And of course this answer will change frequently due to fluctuations in gasoline price.
Yes, the best way to think about this question is "cents per mile", whether in kWh for an EV or in gasoline cost for an ICE car.
I have an advantage in this calculation because I measure the electricity I use in my LEAF from the wall (see link in signature below). Over the last year and a half I am at
3.91 miles/kWh from the wall (winter and summer, preheating, all of it). My electrical rate is 13.7555¢/kWh so that works out to
3.5¢/mile (although since I have solar panels the actual marginal cost of electricity for my car is zero). That number would be lower for someone with less expensive electricity rates:
Code:
@4.0 miles/kWh (measured from the WALL)
3¢/kWh = 0.75¢/mile
4¢/kWh = 1.00¢/mile
5¢/kWh = 1.25¢/mile
6¢/kWh = 1.50¢/mile
7¢/kWh = 1.75¢/mile
8¢/kWh = 2.00¢/mile
9¢/kWh = 2.25¢/mile
10¢/kWh = 2.50¢/mile
11¢/kWh = 2.75¢/mile
12¢/kWh = 3.00¢/mile
13¢/kWh = 3.25¢/mile
14¢/kWh = 3.50¢/mile
15¢/kWh = 3.75¢/mile
16¢/kWh = 4.00¢/mile
The cost of gas for an ICE car depends on the mileage and the gas price. Where I live gas is currently at $3.70/gallon. So the cost would be:
Code:
@$3.70/gallon:
20 mpg = 18.5¢/mile
30 mpg = 12.3¢/mile
40 mpg = 9.3¢/mile
50 mpg = 7.4¢/mile
Your mileage comparison would depend on:
1) Mileage efficiency of the EV
2) Charging efficiency of the EV
3) Gas prices
4) mileage of the ICE car used for comparison
The best way to get a handle on (1) and (2) is to measure from the wall. Otherwise, you can get an idea of (1) by using the mileage meter in the LEAF; mine is quite accurate (completely consistent with mileage from the wall) but some have reported that it isn't very accurate. YMMV.
For charging efficiency (2) you can use 75% if charging at Level 1 (120 V) or 86% if charging at Level 2 (240 V, 3.3 kW). It will be somewhat higher for charging at 6.0 kW.
[However, I consistently find that I get about 88-90% charging efficiency because I rarely charge to "100%"; charging to 100% is less efficient than charging to 80% or less.] Be aware that preheating will also lower charging efficiency somewhat and this is hard to quantify without a wall meter.
The numbers for (3) and (4) will depend on gas prices and the gas mileage of the car used for comparison. But both are easily attainable.