MPG ratings for PHVs are stupid

Agreed!

 

+1

 

+2
I am a critic of MPGe I think it is very misleading.

 

This is a start for the new "E" revolution.

 

maybe a combo of battery efficiecy and size, curb weight and drag or something that would account for the cars design and not some test that cannot be replicated in real life.

 

I do think MPGe is a useful value. Electricity isn't free, so I do want to know if one car uses more electricity than another. That said, I agree, the sticker needs to state the actual miles you can do on battery (with a YMMV warning I guess), and the gasoline MPG.

 

I do think MPGe is a useful value. Electricity isn't free, so I do want to know if one car uses more electricity than another. That said, I agree, the sticker needs to state the actual miles you can do on battery (with a YMMV warning I guess), and the gasoline MPG.

Read more: http://priuschat.com/threads/mpg-ratings-for-phvs-are-stupid.121165/#ixzz2IjhRMo00

and which entity will enforce and mandate this new changes if this where implemented? DOT?

 

How is MPGe calculated? Is it how many miles I can get from EV at the cost of a gallon of gas? So the cost currently for a gallon of gas is $3.60. My cost for electric is /kwh is $0.08. Say it takes 3.3 kwh per charge ($0.264) which nets me 12 miles. That equates to 0.022 cents per mile. 3.60 / 0.022 = 163 MPGe. Am I doing it right?

 

EV range should be one comparable number posted by EPA and DOT.

Engine only MPG should be another one using the current MPG calcs.

Users can then calculate their MPG range based on their daily usage.

With an EV range of 20 miles and an ICE mpg of 37, a Ford Energi would give me 63 mpg on my daily usage.

With an EV range of 11 miles and an ICE mpg of 50, a Prius Plug In would give me 64 mpg on my daily usage.

With an EV range of 300 miles and no ICE, a Tesla Origin X would use no gas at all.

 

No, MPGe is used to compare electric efficiency in the term that everyone is familiar with; miles per gallon (mpg). A gallon of gas burned generates 115,000 BTUs. To generate the same amount of heat with electricity takes 33.7kWh. So one gallon of gas is equivalent to 33.7kWh. So then they determine how far the vehicle will travel on 33.7Kwh. For the PiP, I believe the EPA calculated around 8.5 miles per 3kWh charge (or thereabouts). So ((33.7/3)*8.5) = 95.4MPGe. I believe that is what the Monroney statement displays for the PiP.

 

Thanks for the breakdown. I always wondered how they came up with the MPGe.

I still think my calculation means more to me though. To me, that is my equivalent lol.

 

Then what you want is MP$ .

Here is a link to MPGe definition. Miles per gallon gasoline equivalent - Wikipedia, the free encyclopedia

 

Well you are right that your calculation means more for your individual stats and understanding your cost of ownership. But to compare “efficiencies” of the two fuel sources between you and me, we need to compare apples to apples. How can you compare performance to me when I’m paying $3.76 a gallon and $0.03591/kWh. The MPG and MPGe gives us that comparison regardless of the ever changing cost of our fuels.

 

Understood. I appreciate the explanation.

 

I'm not sure people really care to compare MPG or MPGe between friends. What they want is a way to predict what they will spend to operate one vehicle vs another vehicle. MPG was a nice proxy when a gallon of gas was the largest contributor to operating costs. With an EV or PHEV, car washing could be a larger component than gasoline or electricity.

I am running about $1.76/100 miles for the first 10,000 miles on my PHEV.

 

Fuel Economy gives good comparisons of operating costs.

Interesting that Prius plug is rated 95 MPGe with .2 gal/100 mi of gas plus 29 kW-hours/100 mi vs. Ford C-MAX Energi rated 100 MPGe with 0 gal/100 mi of gas plus 34 kW-hours/100 mi.

$900 per year to operate both vehicles all things being equal.

 

MPGe is supposed to be for pure EV only.
Learn More About the Fuel Economy Label for Plug-in Hybrid Electric Vehicles

I say supposed to because the PiP cannot complete the EPA test cycle without turning on the ICE.
Compare Side-by-Side
Therefore if you look at the EPA comparison between the PiP and the C-Max, you will see that the C-Max gets 100 MPGe using up 34 kwh/100 miles while the PiP gets 95 MPGe using up 29 kwh/100 miles. What gives? The PiP should have a 116 MPGe rating. 33.7 kwh/29 kwh x 100 miles = 116 MPGe. It's because 0.2 gallons of fuel was used when the ICE turned on to complete the test cycle.

And based on the below thread, you can't say it's an unfair test because the PiP ICE does have a higher tendency to turn on than a C-Max or a Volt and apparently the Accord as well.
ICE in EV Mode ... Again | PriusChat

 

So two months from now you report $1.91/100 miles...... did your cost per unit of fuel go up or did your MPG/MPGe go down; you can't tell. Looking at your MPG/MPGe will indicate if your driving routine has changed, (more highway miles, spouse started driving, etc) or you have a mechanical problem (tire inflation down, brakes/bearing dragging etc). MPG/MPGe provides a way to compare your car to another, or your performance over time. Knowing the MPG/MPGe allows you to predict your future costs as energy prices change or can alert you to mechanical changes/problems.

 

EPA said it takes 3.2 kWh to fully charge it, probably using the 120v charger included.

EPA test includes both the city and highway cycle. PiP performed full electric in the city cycle. However, in the highway cycle, the gas engine triggered (while continuing to deplete the battery -- EV BOOST), using 0.0215 gallon of gas. The battery depleted after 11 miles.

For the 11 miles, PiP used 3.2 kWh of electricity and 0.022 gallon of gas (less than 2 eggs). 11 miles / [(3.2 kWh/33.7 kWh)+0.0215 gal] = 95 MPGe.

EPA label shows the breakdown for 95 MPGe as Electricity (29 kWh/100mi) + Gasoline (0.2 gal/100mi).

Personally, I am doing 128 MPGe on electric miles and 54 MPG on gas miles (15% charging loss added).