Questions about MPG equivalent

[Galiano]

I'm wanting to be clear on the MPG equivalents I see quoted in various sources. I hope you will pardon me being a bit dense about this but I'm new here. I hope to purchase a 2013 Leaf as soon as they are available here in Canada. ( Soon I hope ! )


So what goes into this MPG equivalent calculation ?

Given that our gallon ( Imperial ) is about 20 % larger than the US gallon, is it reasonable to assume the MPG equivalent will be 20 % higher ?

 

[Nubo]

The calculation is based on the energy content of a gallon of gasoline, which iirc, is somewhere betweeen 33 and 34 kWH.

What this means is the LEAF has about a 3-quart "tank" It also means ICE cars are wasting the vast majority of the gasoline they burn.

The Canadian MPGe will be higher if they are based on imperial gallons since an imperial gallon has an energy content of around 40kWH.

 

[mksE55]

I based mine on the cost of gasoline and standard mileage the car of your choice gets. like 1 gallon of gas $3.20 camary gets 35 miles to a gallon.
so my leaf with new full battery charge holds about 21 kWh means It would cost $2.10 to charge full. I pay 10cents a kW. I could drive 84 miles on a charge. i would be getting about 128 miles to a gallon(cost of gasoline). 84 miles and about 50% more to equal the 3.20 cost. rough estimate. some have driven about 95-100 miles on a charge the are looking at 150 miles to a gallon. it gets better the more gas cost as well. but worse if you electricity is higher also. everyone is alittle different but this formula is more real world for your application. I was driving a 18 mpg car before I switches so the savings are even greater. Hope this helps.

 

[apvbguy]

The calculation is based on the energy content of a gallon of gasoline, which iirc, is somewhere betweeen 33 and 34 kWH.

What this means is the LEAF has about a 3-quart "tank" It also means ICE cars are wasting the vast majority of the gasoline they burn.

The Canadian MPGe will be higher if they are based on imperial gallons since an imperial gallon has an energy content of around 40kWH.

fwiw the last time I was in Canada they sold their fuel by the liter, AFAIK the only place that might be still using the larger imperial gallon is the UK

 

[RonDawg]

The Canadian MPGe will be higher if they are based on imperial gallons since an imperial gallon has an energy content of around 40kWH.

fwiw the last time I was in Canada they sold their fuel by the liter, AFAIK the only place that might be still using the larger imperial gallon is the UK

Canada publishes fuel economy ratings as both MPG and L/100 km:

http://oee.nrcan.gc.ca/cars-light-trucks/buying/energuide-label/5744" onclick="window.open(this.href);return false;

 

[apvbguy]

The Canadian MPGe will be higher if they are based on imperial gallons since an imperial gallon has an energy content of around 40kWH.

fwiw the last time I was in Canada they sold their fuel by the liter, AFAIK the only place that might be still using the larger imperial gallon is the UK

Canada publishes fuel economy ratings as both MPG and L/100 km:

http://oee.nrcan.gc.ca/cars-light-trucks/buying/energuide-label/5744" onclick="window.open(this.href);return false;

that I didn't know, I've bought fuel there but I never shopped for a car there

 

[Galiano]

" The calculation is based on the energy content of a gallon of gasoline, which iirc, is somewhere betweeen 33 and 34 kWH.

What this means is the LEAF has about a 3-quart "tank" It also means ICE cars are wasting the vast majority of the gasoline they burn.

The Canadian MPGe will be higher if they are based on imperial gallons since an imperial gallon has an energy content of around 40kWH. "


I think most " old timers " like me here in Canada still think in terms of miles per gallon.

So if I use 110 miles per US gallon x about 1.2 I get around 130 miles per Imperial gallon. But I suppose all this is dependant on cost of gasoline, hydro rates etc. ? I think I won't be far off the truth if I tell my friends that my new Leaf gets around 125 mpg equivalent ( Imperial gallons )

One of my good pals drives an SUV :lol:

 

[Nubo]

"
I think most " old timers " like me here in Canada still think in terms of miles per gallon.

So if I use 110 miles per US gallon x about 1.2 I get around 130 miles per Imperial gallon. But I suppose all this is dependant on cost of gasoline, hydro rates etc. ?

I think I won't be far off the truth if I tell my friends that my new Leaf gets around 125 mpg equivalent ( Imperial gallons )

You are confusing two issues

1 - Miles per unit of energy. This enables a comparison of the electric car with gasoline cars in terms of energy efficiency.

2 - Monetary energy cost per mile. I.e., you want to compare how far the cars go for the same amount of money.

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.

 

[ELROY]

The Nissan is very efficient. More efficient than a ICE motorcycle.
But the bottom line is what it costs you to run based on your utility costs.
The cost that some people pay can make it no more economical to run than a Prius.
With my superoffpeak rate of 10 cents/kWh, I can easily drive 50 miles on about $1.75. Or more than twice as economical as a Prius.

 

[dgpcolorado]

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.

...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:

@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:

@$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.

 

[Galiano]

This is all very interesting and really helps with my EV education. I'm convinced that I will have to answer questions from doubters once we take delivery of our new Leaf. I'm curious if this is the norm ?



What an excellent forum this is and I thank you all for your replies so far.

 

[cwerdna]

I haven't read this thread carefully, but personally, I care very little about MPGe numbers, esp. to compare to ICEVs. I might care somewhat to compare relative efficiency between various PHEV and BEV models.

Besides the Imperial gallon being ~20% larger, Canada's FE ratings for ICEVs are out of whack w/current US figures, even if you convert them to miles per US gallon. (Google makes for a great converter. E.g. Google for 60 miles per Imperial gallon in miles per us gallon.)

See below for re: the differences in FE testing.
http://www.autonorth.ca/home/2011/12/2/canadian-vs-american-fuel-efficiency-why-the-big-discrepancy.html" onclick="window.open(this.href);return false;
http://web.archive.org/web/20120903133543/http://www.tc.gc.ca/eng/programs/environment-fcp-faq-139.htm" onclick="window.open(this.href);return false;
http://www.cbc.ca/news/canada/story/2011/11/27/f-fuel-efficiency-compare.html" onclick="window.open(this.href);return false;