I've got a math question about HEV vs BEV...

[Logal727]

Ok, so I was driving my wife's 2019 Ioniq Hybrid (not plug-in) today, and I was worried it was at a quarter tank and it would need gas soon, but then I looked at the DTE and it said 204 miles. This thing is crazy efficient, 55 mpg, love it.

Anyways, I was trying to figure out how to compare the fuel efficiency of an HEV to the Mach-E. My guess is the HEV is gonna be more efficient? Anyone know a calculation to do this as a fair comparison and not the dumb MPGe?

Would it be figuring out the miles per kWh of the HEV?

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[Maquis]

A gallon of gas is about 33 kWh. Do the math.

 

[kltye]

Ok, so I was driving my wife's 2019 Ioniq Hybrid (not plug-in) today, and I was worried it was at a quarter tank and it would need gas soon, but then I looked at the DTE and it said 204 miles. This thing is crazy efficient, 55 mpg, love it.

Anyways, I was trying to figure out how to compare the fuel efficiency of an HEV to the Mach-E. My guess is the HEV is gonna be more efficient? Anyone know a calculation to do this as a fair comparison and not the dumb MPGe?

Would it be figuring out the miles per kWh of the HEV?

More efficient in full EV-only mode? Probably, because it's lighter. But once you fire up the gas engine, you're losing over 50% of the energy in gasoline to heat, even with fancy Atkinson cycle engines. So no - as far as moving cars, gas engines will never be as efficient as EVs (at least as for as in-car energy conversion).

 

[ebeponyan]

It depends on what you mean by fuel efficiency, and will be difficult to nail down a meaningful comparison. Gas is super energy dense and ICE engines, even efficient ones, lose more of that power to heat than they harness for propulsion. Your BEV will always win the direct kWh comparison, but that comparison is a little disingenuous. The kWh in your battery come from somewhere, and that somewhere could be predominantly coal or 100% renewable depending on where you plug in. In general though, whatever is getting extracted/refined/burned to fill up your BEV is going to be done more efficiently at a central power plant than distributing gas out to individual ICE vehicles and burning it there.

 

[AliRafiee]

A gallon of gas is about 33 kWh. Do the math.

Depends on the car. My last EV was doing 4.6 miles/kWh. The Mach E does 3.3 miles/kWh.
And my Mustang GT was doing 13 MPG.
His does 55 MPG.
According to your calculations I need to have 330 kWh battery to go the same distance as my Mustang.

 

[Logal727]

It depends on what you mean by fuel efficiency, and will be difficult to nail down a meaningful comparison. Gas is super energy dense and ICE engines, even efficient ones, lose more of that power to heat than they harness for propulsion. Your BEV will always win the direct kWh comparison, but that comparison is a little disingenuous. The kWh in your battery come from somewhere, and that somewhere could be predominantly coal or 100% renewable depending on where you plug in. In general though, whatever is getting extracted/refined/burned to fill up your BEV is going to be done more efficiently at a central power plant than distributing gas out to individual ICE vehicles and burning it there.

Ok, yes, this is why I'm having trouble finding a comparison that works.

 

[Logal727]

Depends on the car. My last EV was doing 4.6 miles/kWh. The Mach E does 3.3 miles/kWh.
And my Mustang GT was doing 13 MPG.
His does 55 MPG.
According to your calculations I need to have 330 kWh battery to go the same distance as my Mustang.

Yeah, the Ioniq HEV has a 10 gallon tank, so essentially a 330 kWh equivalent as well, but should we take into account the size of the hybrid battery pack however small?

 

[Blue highway]

Efficiency is pretty easy to compare, but when people say efficiency they often mean something other than efficiency.

In terms of efficiency...

A non plug in HEV is simply a gas car. Efficiency in this case is most simply MPG
BEV efficiency can be expressed MPGe for 1:1 comparison with a gas car.

In your example your Ioniq gets 55MPG, my MME gets 100 MPGe. This is about as apples to apples as it gets.

 

[Logal727]

Efficiency is pretty easy to compare, but when people say efficiency they often mean something other than efficiency.

In terms of efficiency...

A non plug in HEV is simply a gas car. Efficiency in this case is most simply MPG
BEV efficiency can be expressed MPGe for 1:1 comparison with a gas car.

In your example your Ioniq gets 55MPG, my MME gets 100 MPGe. This is about as apples to apples as it gets.

OK, thank you, I guess I was overthinking it.

 

[CompilerBreak]

It was more the range that I noted when comparing, you typically get a close to normal sized gas tank but also much higher hybrid efficiency in the right situation. So a ~300 miles ICE range becomes more like 500+

With a 10 gallon tank that's pretty impressive still though.

 

[JohnFoxeSheets]

Efficiency is pretty easy to compare, but when people say efficiency they often mean something other than efficiency.

In terms of efficiency...

A non plug in HEV is simply a gas car. Efficiency in this case is most simply MPG
BEV efficiency can be expressed MPGe for 1:1 comparison with a gas car.

In your example your Ioniq gets 55MPG, my MME gets 100 MPGe. This is about as apples to apples as it gets.

All true, but.... eMPG is kinda a made up number based on a bunch of assumptions. If you're interested in cost vs. pure efficiency, then the price of electrons vs. the price of dead dinosaurs becomes an overwhelming factor. Here in expensive gas and expensive electricity Cali (ok, well expensive everything), the last time I did a quick calculation the cost breakeven for my ~3 m/kWh average MME GT was about 30 MPG. So Chris's wife's Ionic would be substantially cheaper to drive, though not nearly as much fun!

 

[Maquis]

Depends on the car. My last EV was doing 4.6 miles/kWh. The Mach E does 3.3 miles/kWh.
And my Mustang GT was doing 13 MPG.
His does 55 MPG.
According to your calculations I need to have 330 kWh battery to go the same distance as my Mustang.

The amount of energy stored in a gallon of gas does not vary by car. It’s the same whether it’s in a gas tank or underground storage at the gas station. (Notwithstanding volume changes with temperature).

 

[Blue highway]

All true, but.... eMPG is kinda a made up number based on a bunch of assumptions. If you're interested in cost vs. pure efficiency, then the price of electrons vs. the price of dead dinosaurs becomes an overwhelming factor. Here in expensive gas and expensive electricity Cali (ok, well expensive everything), the last time I did a quick calculation the cost breakeven for my ~3 m/kWh average MME GT was about 30 MPG. So Chris's wife's Ionic would be substantially cheaper to drive, though not nearly as much fun!

there is nothing made up about MPGe.

 

[theduke]

A gallon of gas is about 33 kWh. Do the math.

Of which only ~18% can be used for locomotion. The rest is lost as heat.

 

[JohnFoxeSheets]

there is nothing made up about MPGe.

Well let’s just say that of cost is the concern, MPGe doesn’t come close to telling you the whole picture…

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