MPGE vs MPG

[Chris Hall]

I like the idea of the 4xe, but it wouldn't work for me. I have actually been browsing Rivians for the better half. Mostly because they are somewhat local and decent range.. My question is what is the actual range. Is the 25 miles in town slow stop n go? How far will it go at 65? Will the battery make it a full tank? Or am I stuck with just the 4 cylinder after 100 miles of driving? Is the winter range comparable to summer range? I assume a lift and large tires would kill the electric range. There is a pretty good range penalty for just putting larger rims on a Tesla according to there literature. If someone has the answers please enlighten me. Also if anyone has a knowledgeable opinion on a rivian feel free. I know I know it's a Jeep site.

I think your questions show a great understanding. It would be nice to know a lot of these answers. I’ve wondered how the soft too vs the hard top will impact range. I know the vehicle will keep the battery at some level of charge when in hybrid mode. So there will always be a little there. And yes, tires will make a difference. To what extent, no one knows yet. These are all questions we’ll have to find out together.

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[Chris Hall]

As I understand it MPGe is a number that gives you a comparison to the cost of gas in a traditional car. So a pure electric vehicle that gets 50 MPGe that number is telling you that the cost they expect you to pay for the electricity to go 100 miles is about the same as what a traditional car that gets 50 MPG would cost in gas.

For a plug in hybrid, like the 4xe is (or the prius prime, or the chevy volt, or the chrysler pacifica) needs two sets of numbers. A MPGe for when you're running on electric only, and a MPG for when you're running on gas. It's not possible to combine those two numbers into one that is usable in anyway. With the 4xe the first 25 miles your cost of electricity will be equivalent to that of a 50 MPG car. past that when you're running on gas you'll be getting Wrangler fuel economy.

Of course MPGe kind of goes out the window when you start getting free charging at the grocery store you're shopping at or the restaurant you're eating at or at your work.....

That's in the neighborhood but not quite the right street when it comes to what MPGe is. I copied this from an article written by US News. I'll put some links down below.

What is MPGe?
MPGe is the abbreviation for “miles per gallon of gasoline-equivalent.” It’s an energy efficiency metric that was introduced by the Environmental Protection Agency (EPA) in 2010 to compare the amount of energy consumed by alternative fuel vehicles to that of traditional gas-powered cars. If a vehicle uses non-liquid fuels that aren’t burned and gets its power from electricity or compressed natural gas, it’s rated in MPGe. This is the calculation you will see on an electric car’s window sticker.

How Is MPGe Calculated?
According to the EPA, burning one gallon of gas produces 115,000 BTUs (British thermal units). To generate the same amount of heat by way of electricity, it takes 33.7 kilowatt-hours (kWh). Kilowatt-hours is the standard energy unit for electricity.

In simplified terms, if an electric vehicle can travel 100 miles on 33.7 kWh of electricity, the EPA rates it at 100 MPGe. As you can see, this would be a very efficient vehicle, because a gas car would have to travel 100 miles per gallon to be equivalent.

You are right about needing two different ratings for PHEVs. That's how FuelEconomy.gov does it. When it's an EV it give you the MPGe rating, when it's an ICE it gives you the MPG. PHEVs receive both ratings.

https://cars.usnews.com/cars-trucks/what-is-mpge
https://cleantechnica.com/2019/07/19/what-the-heck-is-mpge/
https://en.wikipedia.org/wiki/Miles_per_gallon_gasoline_equivalenthttps://www.fueleconomy.gov

 

[Roverhi]

They said 'Almost 400 mile range' early on in the videos, I'd assume that means total possible range regardless of what's propelling the Jeep? But there has been Zero reviews by actual real people so nobody really knows.
I am not a hater at All I want this to be a huge success but the lack of communication on a complicated new vehicle does not bode well.

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If I'm reading the information right, on the freeway and/or longer drives the 4xe is an overweight 4 cylinder JLU that gets low 20's gas mileage. Especially on the 2nd tank of gas on a long trip and/or in the mountains where the batteries would be drained quickly.

What happens on an overland adventure where you'd like the instant torque of the electric motors but the battery has been drained getting there. I know you could go on battery reserve mode but doesn't that disable electrical assist and force you to essentially rely on a turbo lag 4 cylinder engine where the instant torque of the electrics would be most beneficial.

The hybrid mode will certainly cut down or almost eliminate running the gas engine with overnight charging but be of limited benefit once you've gone the 25 mile electric range. I'm trying to decide whether the diesel would be a better choice for off-road use given the limited electric range boost.

 

[Shasta_Steve]

How Is MPGe Calculated?
According to the EPA, burning one gallon of gas produces 115,000 BTUs (British thermal units). To generate the same amount of heat by way of electricity, it takes 33.7 kilowatt-hours (kWh). Kilowatt-hours is the standard energy unit for electricity.

In simplified terms, if an electric vehicle can travel 100 miles on 33.7 kWh of electricity, the EPA rates it at 100 MPGe. As you can see, this would be a very efficient vehicle, because a gas car would have to travel 100 miles per gallon to be equivalent.

You are right about needing two different ratings for PHEVs. That's how FuelEconomy.gov does it. When it's an EV it give you the MPGe rating, when it's an ICE it gives you the MPG. PHEVs receive both ratings.

https://cars.usnews.com/cars-trucks/what-is-mpge
https://cleantechnica.com/2019/07/19/what-the-heck-is-mpge/
https://en.wikipedia.org/wiki/Miles_per_gallon_gasoline_equivalenthttps://www.fueleconomy.gov

Good information to know what they are thinking. For work I am a power plant operator in a gas turbine. By this line of thinking they plan on using almost the whole 17 kw hour battery to go 25 miles or get 50 MPGe.

Now here is where I think that number is almost useless . A power plant, (or power generation by any means) is not 100% efficient. Of course neither is a combustion engine but that is accounted for with a MPG number. In the power plant I operate 115000 BTUs of natural gas will produce between 14-15 KW of electricity. Some of the newer plants will probably go 17-18 kw per that amount. In reality you are still looking at about the same amount of energy to go similar distances.

Now of course there are lots of ways to produce electricity that don't require fossil fuels and EV's will most likely be getting charged at night so that helps things out. I still think they are a positive as natural gas, burned in a power plant, will have less emissions than a similar gas engine. And there are a ton of no or low carbon forms of generation.

edit: number of BTUs to produce electricity

 

[Sboden]

er
If I'm reading the information right, on the freeway and/or longer drives the 4xe is an overweight 4 cylinder JLU that gets low 20's gas mileage. Especially on the 2nd tank of gas on a long trip and/or in the mountains where the batteries would be drained quickly.

What happens on an overland adventure where you'd like the instant torque of the electric motors but the battery has been drained getting there. I know you could go on battery reserve mode but doesn't that disable electrical assist and force you to essentially rely on a turbo lag 4 cylinder engine where the instant torque of the electrics would be most beneficial.

The hybrid mode will certainly cut down or almost eliminate running the gas engine with overnight charging but be of limited benefit once you've gone the 25 mile electric range. I'm trying to decide whether the diesel would be a better choice for off-road use given the limited electric range boost.

This YouTube video should help you with your questions.

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