I assume they mean the amount of energy that is released by burning that gallon of gasoline, not the total amount of energy according to E=mc2. 🤨🤔😅

Indeed! You'd get a long way on the latter.

This seems like an arbitrary relationship that is not very useful and may actually be misleading for comparing EVs to GVs.

It's useful in so far as it takes into account the cleanliness of the electricity generated and shows that EVs aren't pollution free. But of course local circumstances vary such as if you have solar at home for charging.

But it might be a useful metric for comparing EVs to each other.

Only if a consistent g/kWh figure is used. Better to use the m/kWh or kWh/100km figures. But like gas mileage, real world figures can vary hugely from test figures.

 

MPGe is complete and utter nonsense.

 

So, in your opinion, it is of no value in comparing EVs?

 

The other issue being too that mi/kWh shown in a Phev/bev can be that far out from the truth so as to be pretty much pointless anyway.

I'm absolutely certain that my golf GTE doesn't take into account the PTC heater when giving the mi/kWh rating.

 

The other issue being too that mi/kWh shown in a Phev/bev can be that far out from the truth so as to be pretty much pointless anyway.

I'm absolutely certain that my golf GTE doesn't take into account the PTC heater when giving the mi/kWh rating.

There are also various offsets: preheating the car while it’s plugged in represents a use of energy that evades the m/kWh measure. There needs to be a kWh/time usage per person

 

Stick with miles per kWh to compare EV’s. MPGe is just someone’s attempt to compare MPG to EV efficiency. I wouldn’t trust that any more than an EPA or NEDC rating.

For starters, EV’s are most efficient around town whereas a petrol car is more efficient at speed. They are apples and pears.

I just take a high level simplistic view. 3 miles per kWh or less is rubbish. 4 to 4.5 is average, and 5 and above is good. If you have to make a comparison to a petrol car, think of the above as like getting 30, 40 or 50 miles to the gallon.

 

I just take a high level simplistic view. 3 miles per kWh or less is rubbish. 4 to 4.5 is average, and 5 and above is good.

Yeah that works for small EVs or efficient like Ioniq electric or purely pooting around town at 20mph. Motorway driving at 70mph and you won't see 4-4.5.

A large SUV or Audi e-tron might get 3 miles per kWh as their best figure. And of course living where it's cold most of year will have a large impact. The person also doing many 5mile popping to shops/school doing lots of stop/starts will have a much worse avg than over a longer distance where the battery is at optimal temps at a constant speed.
The heavy footed driver might get 2.5 and the hypermiler gets 5 in the same conditions.

i would say it's actually quite hard to compare like for like.

 

I haven't bothered to look before but as far as I can see they are saying

33.7 kWh of electricity = 1 gallon of gas

And I'm assuming that's US gallon 3.785 liters rather than the UK 4.546 litres

 

MPGe is a variation of miles per kWh (or kWh per 100km in fully metricised countries), pretty much only used in the more gas-centric US.

It's not used in the UK/Europe and doesn't directly help you know how far your EV can travel.

However, where the US is arguably more realistic than the rest of the world is with its EPA range figures: these are a bit more accurate for most mixed-use driving than WLTP or the older NEDC range figures.

 

In the US, the MPGe thing is to try to put some data on the Monroney stickers. It's complete nonsense from a consumer's perspective, but it's the law in the US to have the stickers so they have to put something on it.

Forget it. For your purposes, all BEVs will have roughly the same efficiency.

You might be interested in range, but depends on your usage cycles.

If you are not doing long distances, and don't want a performance car then; a) forget FWD/RWD, irrelevant, b) forget range and MPGe.

Buy the car you like for the best price you want to pay. Trust me, anything more will be over-thinking it.

Maybe in the future when there is even more range and more choice and you have some experience, you can refine your search. For now, pick a car you like and feel comfortable in.

I mean, don't for a moment think that I am trying to put you off doing any research, you might enjoy it, but once you get a BEV you'll see it was a bit of a waste of time. I just hope any research you do does not persuade you away from a car you might have preferred.

 

To determine MPGe ratings, the EPA uses the precise amount of electric energy that's equal to the energy in one gallon of gasoline, according to Green Car Reports. I assume they mean the amount of energy that is released by burning that gallon of gasoline

I agree that this is a big distraction, trying to derive something that looks like "MPGe". There was a lengthy debate on this thread about trying to get some kind of general perception of the relative energy contents of a litre of fuel and a kWh. In broad terms, a litre of petrol will give you about 2kWh of useful work output. But it would give about 8kWh of heat if you just put a match to it and burned it. A ICE is only about 25% efficient and that is why it gives out a lot of heat, as well as driving the car.

I find that linkage (1 litre = 2 kWh) to be useful when comparing the price of fuels. If petrol is selling for 160 p/litre, then a rapid charger at 80 p/kWh would be about the same price.

You could extend the analogy to fuel efficiency. If your EV does 3.5 miles/kWh, then that would be equivalent to 3.5 mile/kWh x 2 (kWh/litre) x 4.5 (litre/gallon) = 31.5 mpg.

 

I agree that this is a big distraction, trying to derive something that looks like "MPGe". There was a lengthy debate on this thread about trying to get some kind of general perception of the relative energy contents of a litre of fuel and a kWh. In broad terms, a litre of petrol will give you about 2kWh of useful work output. But it would give about 8kWh of heat if you just put a match to it and burned it. A ICE is only about 25% efficient and that is why it gives out a lot of heat, as well as driving the car.

I find that linkage (1 litre = 2 kWh) to be useful when comparing the price of fuels. If petrol is selling for 160 p/litre, then a rapid charger at 80 p/kWh would be about the same price.

You could extend the analogy to fuel efficiency. If your EV does 3.5 miles/kWh, then that would be equivalent to 3.5 mile/kWh x 2 (kWh/litre) x 4.5 (litre/gallon) = 31.5 mpg.

I would say (and have), it's closer to 1 litre for 3kWh. (Even 4kWh if you are comparing with a latest-tech diesel)

I think claiming ICE are 20% thermal efficient is boring old hat fud, a bit like saying BEVs all catch fire easily.

I mean, you can use a '2' ratio if you like, but it's meaningless anyway, one way or another.

 

I am going to propose the sBA. This is the performance of a soccer player expressed as an equivalent cricket batting average. It allows you to compare the relative merits of a soccer player with a cricket player (with the right assumptions) and is probably more useful than eMPG.

 

Basically anything has more merit than MPGe!

If only stroppy knickers stopped being so butthurt she'd figure that out for herself...

 

WLTP measures efficiency for 5 phases (city, town, rural, highway plus a combined figure). Manufacturers quote the combined figure.

Options such as sunroof or leather interior affect weight and thus efficiency, and these are measured by WLTP too. Ev-database.org lists the WLTP TEH and TEL figures (in Wh/km) - TEH being with the heaviest set of options and TEL with the lightest.

EVDB also lists both "from the battery" ("vehicle consumption") abd "from the wall" ("rated consumption", which accounts for charging losses).

EVDB doesn't provide the WLTP ratings on the 4 different cycles but it does give city, highway and combined "real energy consumption" figures, for both cold and mild weather, which give an indication of how efficiency varies with usage and temperature.

For example, Ioniq6 RWD has rated efficiency 143-160Wh/km (TEL to TEH), with estimated real efficiency being 109 city, 164 highway and 135 combined.

 

Miles per kwh works fine for me in fact it works better than mpg as not only does it show indication of efficiency of the car and your driving and impact to temp it also simplifies the calculation of the cost for me 4p per mile.

I don't use it to compare ICE to EV though (though it is in the calc used), what I do for that is to work on the ICE range to a tank of fuel cost as that seems easier for none EV owners to get their heads around - aka tank gets you 450 miles of range £1.45 a litre so £45 my cars annual average is 3 kwh per mile so 450/3 * 12p per kwh is £18 - so a full tank comparison is £18 v £45.

 

The problems all arise when people try to achieve what the manufacturer is claiming.

"I can't get the miles you've advertised the car to be able to achieve"

"Oh yes sir, ignore those figures you'll never be able to achieve those, they're only a guide to compare with other vehicles".

We never used to buy petrol and diesel cars based on thier expected "range". We just used to look at the engine size and understand roughly what fuel economy we might get.

 

The worst case of WLTP Vs real life has got to be the BZ4X with 317 miles shown on their site.

They later revealed the battery was 71.4 gross not net meaning you would need 5 miles+ per kWh to get anywhere near that.

And it turned out from real world tests in 5°c it caps the actual usable at 60 instead of 64 and you get an actual 2.2 miles per kWh.

So 132 miles Vs 317 miles 🫣

 

Well an interesting discussion and some surprisingly strong opinions.

I have no particular problem with MPGe. We don’t use it in Europe but it’s fundamentally miles per kWh multiplied up by the kWh in a US gallon of gas. Not sure if thatshould be so problematic for people but seems it is. You could equally divide mpg for ICE vehicles by 33 to get a mi/kWh figure for ICE cars. It’s a very rough and imperfect method to compare but surely serves a (limited) purpose. The same limited purpose that having an official EPA MPG figure serves for ICE vehicles.

Presumably that’s what was intended to provide a metric to compare efficiency across fuel types that people who don’t already own an EV might understand.

 

You could equally divide mpg for ICE vehicles by 33 to get a mi/kWh figure for ICE cars. It’s a very rough and imperfect method to compare but surely serves a (limited) purpose.

Agree on the surprisingly strong opinions. Not like folks round here at all, eh?

When I want to give myself a laugh, as I fill the ICE once a month, I track just what you say, a mi/kWh figure for the ICE. Its puny 1mi/kWh always makes me giggle.

 

And also of course the cost to you per kW of energy you add to the car. Home charging from solar in a climate that is sunny most of the time, it’s probably better to focus on the size of the solar array you need to install and which home wall box to divert that without drawing from the grid. For someone who has to charge on the fly at public chargers all the time, the efficiency may be vital to reduce their costs (although driving style and speed would probably play a bigger part), but for those of us lucky enough to have home charging and solar, the total running costs come more down to array size, which energy provider you use etc.

 

The US EPA way of measuring MPGe has one singular advantage; it is the energy from the wall.

It is not the energy from the battery to the wheels, as is quoted for EU.

In this way, the US figure does better represent actual cost to consumer, which is the point of the Monroney stickers in the first place.

I think the US has dealt with the situation very constructively.

The MPGe to mi/kWh conversion ratio is purely on the energy content of the fuel. So this does not at all take in to account the car, the engine, the thermal efficiency, it is in fact the ideal 'objective' determination. Unfortunately, without understanding all these things, and as this thread demonstrates few do, it's actually pretty useless.

 

The ideal way for the purposes of the Monroney Act would be to say "10c/mile (assumes $5/gal, or 20c/kWh)", something like that, then it's the same 'number' for BEV, ICE or PHEV.

But I am not in charge of the world, so I am afraid you have to put up with the chaos you all create!

 

How did they come up with the MPGe being equal to 33.7 kWh of charge? Is that just abitrary?

 

Calorific content.

One burns a substance and one measures the heat from it.

Same process for all those kJ (kCal) numbers on the back of your food packets. They just burn the stuff and measure the heat. (Caveat, depends on the substance, they might use an oxidising agent like H2O2 or such if it does not burn well, or dangerously/explosively)

 

MPGe is pretty useful for comparing EVs against each othe. But less useful in an EV vs gas car comparison.
I find the EPA range figures much more realistic than the WLTP ones we get in Europe.

Using EPA range, battery size and typical electricity costs in your state, you can get a fair idea of running costs per mile for an EV. Compare that with typical gas cost per gallon and EPA quoted gas mileage to give a running cost per mile for a gas car.

 

It is amazing that the EPA has come up with a measuring unit MPGe that is based on converting an invariant unit to some arbitrary equivalent based on "equivalence" of energy; it is totally incorrect and misleading! (Only used by USA) Finally, measuring unit should be alike as at European Union with the rest of the world using EEA unit counting CO2 in g/km. However, in both cases EEA and EPA units don’t include the EV battery carbon footprint loss, which makes the data totally unreliable? EV is certified by EPA as a “Zero-emission-vehicle” (ZEV) which is totally wrong and misleading (EEA and the rest of the world does not have such non-technical incorrect certifications); there is no any EV in USA which is not emitting CO2. EV pollution is reverting to the Power plant chimneys. Battery carbon footprint is a constant polluting working additive to any EVs. One of the main purposes of EV is reduction of harmful emissions (CO2). When the renewable energy will overcome and replace the fossil fuel in the future EV will become justifiable.

 

My best way of comparison from EV to ICE car is simplistic enough:
My EV can travel 240 miles and has a 52 KW battery. It costs me €15 to charge at home from 0-100% which equates here in Ireland to approx 2 imperial gallons of Petrol / Diesel.
which means I am getting the equivalent in ICE terms of +- 120 MPG
Obviously if I use an expesive public EV charging point it could cost €40 plus equating to a comparable MPG figure closer to the ICE vehicle of maybe 40MPG. So it depends on the cost per KW/H really!
BTW the figures above are hypothetical as I dont run the EV battery to 0%, or I'd be walking home without it!

 

I charge once a week for £2.70 and I do between 120 and 140 miles on that.
So I suppose that's equivalent of about 300mpg at £6 a gallon of the dirty stuff.

 

That's the only real way, by comparing the economic levels of different cars by bringing them all down to a pence per mile figure, so that they all can be judged against each other.

However, whilst the price of petrol etc is pretty consistent nationwide, that also introduces another large anomaly over the cost of electrons. That can vary from zero at some places, to as low as 7p for overnight tariffs at home, through to 80p per kWh at Public Rapids.

It's easy to reduce a petrol car to pence per mile based on how many miles it can drive per gallon. A typical gallon of petrol today would be £6.10. And an average car will easily manage around 40mpg. So that would be 15.25p per mile. At 50mpg it would be 12.2p per mile. An easy and consistent calculation.

An EV using overnight electrons and managing 3.5 miles per kWh would be 7/3.5 = 2p per mile, and at 4m/kWh = 1.75p per mile. Using home electricity at a standard tariff of 27p for 3.5 and 4 m/kWh that would be 7.71 and 6.75 miles per kWh. And using public Rapids at the most expensive end would be 22.8 and 20p per mile.

This means that it's almost impossible to compare an EV against an ICE in either MPGe or pence per mile without also quoting the cost of the kWhs. The range is 0p per mile through to 25p per mile. But with an ICE it is really easy to quote a pence per mile figure, and can vary between 20p and 10p per mile for most normal cars and off the scale for some very thirsty beast.

The bottom line is that an EV with home charging is much cheaper per mile. From 1/10 the price to 1/2 the price. But with public charging, it can be more expensive per mile.

This calculation becomes even more complex if you try to equate a PHEV costs because in some cases they are never plugged in, and even if they are, they may then always drive on EV only, or sometimes a mix of both, which then varies with the miles per journey. So many variations that it would need a full-size spreadsheet to cope.

 

The other thing to consider is, even on a decent night tariff, your day rate will be more expensive.
In our case we don't use much electric so it's negligible.

 

For me it seems to give as one might take simplifies the matter.

A petrol user saying 40 miles per gallon would likely find the cheapest cost for a gallon rather than quoting some outrageous price paid at the end of nowhere.

So the prices I would use are a gallon of petrol at £6.15
With a kWh costing 7p, the best prices I can get while actually paying.

My gallon therefore buys 87 kWh (87×7=609)
Average miles per kWh is around 3.4 for my car and usage.

So 87×3.4 miles gives me an MPGe of 295 miles which beats 40 MPG hands down.

Just why a year old thread was dug up I'm not sure but petrol might be a bit cheaper now than it was 12 months ago.

Nobody cares how much energy can be released from a gallon of petrol only how far it gets you so using cost to get an equivalent rather than energy as intimated in the OP is really the only way for anything to make sense to anyone.

I'm thinking if someone was to ask me how many miles per gallon my car gets the answer would be it's an EV but it's equivalent to 300 miles per gallon which would be just about as accurate as anyone in a car which claims it gives 40 MPG saying they get 40 MPG, probably moreso.

Gaz

 

If I can go 200 miles in a BEV and 600 miles in a ICE, then the BEV is obviously '200 miles per fill' rather than '600 miles per fill', so ...errrr .... is less efficient!