BEVs Are Efficient: Use 80% Of Energy To Move Car Down The Road

SEP 6 2018 BY MARK KANE 45

BEVs use around four-fifths of the electricity for motivation, while ICE use as low as 12%.

According to US DOE’s Office of Energy Efficiency & Renewable Energy, all-electric cars are very efficient at turning electricity into movement.

The study shows that 77%-82% of energy put into a BEV is used to move the car down the road. That is despite about 16% being lost during charging (we thought it’s much less like 5-10%).

A big part in the result comes from regenerative braking, which alone improves efficiency by 17%:

  • without regenerative braking: 60-65%
  • with regenerative braking: 77%-82%

The rest of the energy is lost or used for auxiliary purposes. The efficiency of conventional cars is the opposite, with the majority of energy put into the tank being lost.

“Unlike conventionally fueled vehicles, electric vehicles experience a loss of energy during “refueling,” with an energy loss of about 16% from the wall power to the battery during charging. However, electric vehicles are otherwise highly efficient delivering 60%-65% of the energy from the wall power to the road even before energy is reclaimed through regenerative braking. When energy gains from regenerative braking are included, the amount of energy used for traveling down the road can rise to more than 80% in the EPA-combined city and highway driving cycle.”

Comparatively, here’s what the DoE says in regards to conventional vehicles:

Not all of the fuel that is put into a car’s fuel tank is used to move the car down the road. In fact, only 12-30% of the energy put into a conventional car is used for that purpose. The rest of the energy is lost to engine inefficiencies or used to power accessories. The amount of energy loss varies depending on the type of driving – city, highway, or combined city and highway. The engine losses, such as exhaust heat and pumping, are higher for city driving than for highway driving. There are no idle losses in highway driving, but losses due to wind resistance and rolling resistance are higher for highway driving than city driving. All in all, there is great potential to improve vehicle fuel efficiencies with advanced technologies, such as advanced engines and hybridization, that address these losses.

And here’s a nifty little graphic to see where all those loses come from:


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45 Comments on "BEVs Are Efficient: Use 80% Of Energy To Move Car Down The Road"

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RE:ICE The rest of the energy is lost to engine inefficiencies or used to power accessories.
0-2% for BEV accessories.

Clearly not comparing apples to apples. At least not for actual use. Where’s the A/C and seat/cabin heat?

There’s no way you’re losing just 2% for A/C or heat and how many days do people not use either.

Cooking the stats once again.

I agree there are a few mistakes here. One is the stated losses from charging. It isn’t close to 16% in current EVs from wall to battery. I wonder if they are including transmission losses from the power plant. If so then they are incorrectly mixing in the calculation for losses that belongs in a different part of the equation, one that corresponds to the losses in refining gas and transporting it.

And as you stated they should show a range for operational losses in EVs and ICEs accounting for weather. They should have a number for best case scenario and worst case scenario even if the worst case scenario fleetwide will be a much smaller percent of lifetime operation.

Edmunds measured 317 Wh/mile from the wall plug vs. 251 Wh/mile from the onboard consumption meter. That implies 80% charging efficiency.

Note: DOE’s 16% may be measured differently. There are losses when discharging the battery under non-ideal conditions. Those losses are clearly included in the 20% loss Edmund’s showed but the DOE might include them in “electric drive system losses”.

If you are willing to add transmission losses then you surely need to take into account how much energy is used and wasted during extraction, or transporting into to the refinery, actually refining it, then transporting to a ship, transport from port to port, then distribution to the gas station to be put into a car’s gas tank to use 20% of what is left to move the vehicle. (Not accounting for evaporative losses here).

If you go that far might as well calculate how much energy is lost in space between the Earth and Sun when captures by farm pv. Let’s go bananas!

And you forgot how much energy never made it into the sun in the first place from the Big Bang (-;

“Where’s the A/C and seat/cabin heat?”

Those are irrelevant to the discussion of efficiency in using onboard power to propel the car down the road.

Efficiency of cabin heating/cooling is a separate subject.

Not even close. Heat comes for “free” from an ICE and is very expensive in a BEV. So having the heat blasting in an ICE does not reduce range, whereas in a BEV could easily make you choose between staying warm and making it to the next charger.
This is one reason the Volt has been the #1 seller in Canada.

I agree that PHEV’s will be better solutions in very cold climates. A good one will use combustion heat to circulate through the battery to get better range & electric efficiency. Though a large enough battery that stays plugged in with preconditioning should work great.

Maybe even a BEV with a solid catalyzed combustor for fuel to make heat exclusively for battery and cabin warming could be an option in the cold? Much less weight and moving parts, allowing a bigger battery. Maybe use alcohol? A heat-based Range Extender—you’d turn it on if it were very cold and you’d be going a long distance. If you’re commuting home and well within the BEV range, just use the battery heat.

0-2% is probably correct as an ICE has to convert that gas to electricity for much of those applications mentioned, EVs do not, so power steering, pumping, wipers, lights, radio, seat heat etc. are inherently more efficient.
AC in an ICE is a large drain on down the road movement, in hot weather we call it the turbo boost button when we switch AC off.
Some heat is free in an ICE, but on an EV it only uses energy when its needed, so may not add up to as much as people think, and with a good COP rating, probably works out well.

Agree: AC / Heat efficiency is a separate subject as every single system is different from each other we can only talk about average efficiency.

Brian, this study seems to be based on EPA cycles, which I don’t think include AC or cabin heat. They did include seat and steering wheel warmers in auxiliary.

Using the A/C isn’t a loss.

What are you talking about? A/C etc. is right there under “Auxiliary Electrical Losses”: 0-2% for ICE and 0-4% for BEV.

I bet these folks spend much more time researching and thinking about this than you did…

I always wondered: is there any point in comparing EVs to ICE’s and saying one is more efficient than the other? It’s not like EVs are a more efficient way to use gasoline or diesel, they don’t run on those so that makes any comparison moot right there. If you are going to use gasoline or diesel for propulsion there isn’t really a way around inefficiency. You’r basically making heat with propulsion as a minor by product.

…and who cares about efficiency anyway, cost is what matters. The two are related of course but if the cost numbers don’t add up favorably a technology isn’t going anywhere. Guess internal combustion is an example of tech that’s very inefficient yet cost effective, mostly because the propellants are cheap residual products of oil refining.

There is a point there.

Right? Efficiency only matters when different solutions compete for the same resources.

You could have an efficient solution in terms of energy produced from a source, in this case mechanical energy to move a vehicle. Then measure the cost to produce that energy. So the cost of the source is a variable that also matters in the equation.

“…who cares about efficiency anyway”

The US DOE’s Office of Energy **Efficiency** & Renewable Energy cares.

Does it still though? This is the Trump era…But yes, efficiency does matter when competing for the same resources, especially if efficiency is directly related to pollution. Don’t expect the average consumer to care beyond cost though.

We need to decouple cost from efficiency. It’s always going to be more expensive to go really deep on efficiency and not be incremental. If we are really serious about going deep on efficiency, then cost needs to be decoupled from efficiency.

Sure, except few will buy a product if it is very expensive even if it is really efficient. We need to be realistic about how consumer markets work.

I know exactly how consumer markets work which is why I was saying cost needs to be decoupled from efficiency. The market is terrible at that which is precisely why things like credits and rebates exist. Those don’t fully decouple cost from efficiency, but they are a start.

Yes it matters. Because other uses of fossil fuels in different thermodynamic cycles to make energy in stationary power is more efficient. Or even better, don’t combust them at all, and use them for manufactured goods.

It also means that when discussing energy needs for EV’s one shouldn’t focus on energy in gasoline vs batteries.

Gasoline is a major intended fraction of oil refining, not a residual. Residual would be awful dirty marine bunker fuel and road bitumen.

Is it really possible to breakdown oil in any mix of products one desires though? That’s not how I understand the refining process to work. Oil fired power plants are pretty rare so clearly that’s not a particularly viable alternative for burning oil based fuels in cars.

In principle, the refiners can select whichever product they want. Yes, their current infrastructure is based around making as much gasoline as is practical. However, I am aware of at least two major engineering houses that are investigating how to transition their FCC units (the primary way of turning non-gasoline fractions into gasoline fractions) towards making plastic precursors.

They both use energy. Different sources of energy (thermal vs electric) but still energy. Civilization is driven on energy usage regardless of source. The more efficiently you can use that energy, the greater chance for success that civilization has.

As an engineer, I’m more concerned with the right tool for the job, regardless of how much that tool costs. I still have to work within cost constraints, but I’m not above spending more to get the right tool (and arguing with bean counters over why that’s better).

It’s been my experience that too much focus on cost and quality suffers. This is why I think cost should be decoupled from efficiency.

Planned obsolescence is not an efficient use of resources and yet, of those who did not adopt it many went out of business. Still it’s better to have an expensive tool that won’t break as often as a cheap one.

“Planned obsolescence” is a more complex topic. Once people have been trained to want new things every couple of years, making things that last longer would actually be a *waste* of resources.

That has more to do with how society in recent years has been organized. It’s been organized around favoring companies and their disposable and planned obsolescence business models rather than favoring a longevity and “fix it first” business model. We used to have the latter before the 80’s.

Using EVs means you leave other potential sources of energy like petrol and diesel unutilized which is great but it’s not about efficiency gain.

The way free markets work is that people will look at prices and quality and buy the best mix. Well…that’s how it should work, prices are easy to compare, quality only establishes itself after long use so price is leading in the the buy decision. That may not be optimal but if EV adoption is to gain traction the price will need to be right.

In an ideal free market, that’s correct. However, there is no such thing as an ideal anything, let alone an ideal free market. In the real free market, there is price manipulation, manipulative advertising, and relentless profiteering at the expense of quality and efficiency. After all, large groups of people maintain that Beta was better than VHS yet VHS won out. Was it really because VHS was the better technology or was it because VHS was promoted by a relentless company hell bent on making huge sums of money over the exclusive licensing and sales of the technology?

As long as most electricity production is fossil-based, comparing efficiency indeed does make perfect sense. As electricity production transitions to renewables, efficiency becomes less relevant (apart from cost optimisation), since using renewable electricity will always be better than a combustion engine, regardless of efficiency…

Yes efficiency in a total battery electric vehicle does ‘matter’ since the further you can drive in a high-efficiency vehicle the less you have to worry about being stranded due to a dead battery. In addition to errors others have noticed, I’ve seen no comment on ‘BATTERY DISCHARGING INEFFICIENCY’, nor in the cooling watt hours needing to be expended to get rid of the HEAT strictly due to that particular inefficiency. The fact that an electric car can – using electricity from the home as a starting point – need less electricity than an equivalent ICE vehicle is a false argument as Ive stated many times since electricity from the wall receptacle has been much more highly processed than the gasoline from the pump. So to assign a high efficiency number from that point on is myopic. As far as ‘source’ to ‘driving a car down the road’ comparison, the average ICE may be around 30% efficient (some Toyotas are over 40% incidentally), my Chevy Bolt is somewhere around 10% efficiency – so people hung up on the ‘high efficiency of EVs’, in an apples to apples comparison will be beaten by an ICE proponent or Ford F-150 driver that… Read more »

6 negatives, no positive responses, yet no one wants to argue the facts. That’s why you don’t see some names here anymore. I asked one former quite active commenter and was told that the up/down voting thing has made the environment worse.

Well, I disagreed with most of your post, but I do completely agree that the up/down voting system has discouraged commenters from posting and probably changed how some respond. I know that I have had to avoid using certain trigger words that might trigger a slew of down votes and cause people to ignore my main point and the rest of what I’m saying.

It’s interesting considering most sites have been moving away from down votes (or even votes all together) yet IEVs used to have no voting, then up votes and now up & down votes. My preference is no votes at all (although, there was a time on MacRumors that I did miss the down votes, but I’m over it).

I don’t think there are many people who actually look at the votes to decide whether they read a post or not…

Perhaps not, but I do think it changes how potential readers approach reading the post. Without votes, reading a post might be more objective. However, with votes, they might assume a bias. For example, someone who sees a lot of (or all) down votes on a comment might assume the commenter is a troll. Without voting, you would not make that assumption until after reading the comment (if it was indeed troll worthy) rather than before. Making the assumption before reading a comment colors peoples preconceptions about the merit of what was said.

I’d also like to point out that Bill has been commenting on IEVs for a long time now and I would not characterize him as a troll. The above was just an example.

Battery discharging losses are probably under “Parasitic Losses” or “Electric Drive System Losses”. Cooling requirements are probably under “Auxiliary Electrical Losses”. As for the “errors” others have noticed, none of them are actually valid as far as I can tell.

This is a comparison of pump-to-wheels efficiency. Of course well-to-pump will add inefficiencies in electricity transmission and generation (though the latter can only be considered losses in a meaningful way if the source is not renewable) — but you get quite significant well-to-pump losses for combustion engine fuels as well. (Something like 30 or 40% IIRC?)

I’d argue that comparing solar generation to fossil fuel refining is not even apples to oranges, but more like apples to rocks. Solar efficiency is not the same as wells to wheels efficiency because you’re not actually “loosing” anything. Solar efficiency is more about how much of the suns energy is being “captured” (it’s a bit more involved than that, but for arguments sake, I’ll leave it at that).

I’d argue that, if you wanted to make this kind of comparison, you’d have to look at the efficiency with which nature utilized the suns energy to grow and reproduce and then the efficiency with which those plants were “fossilized” and turned into oil over the intervening millions of years from the immense pressure of the Earth’s crust. This would obviously be silly and a wasted exercise. When talking about efficiency, it’s probably better to start with your solar panels as the “well” in which case you’ve “extracted” over 90% of the electrons from your PV system (accounting for electrical resistance and DC to AC conversion losses BEFORE charging your vehicle).

Most BEVs use the A/C to cool the air compressor…

BEVs have air compressors?

Hehe, too many after-dinner-drinks…. You rather have to listen to what he means rather than what he says. Unless maybe he’s installed after-market truck air horns on his ev.

Priht out and show this article to those who think electric cars aren’t more efficient. Print out another one about power sources per state, for those who respond: “Yeah, but the power plants all run on coal to fuel them.” 🙂

Wouldn’t matter. They’d just ignore it or call it fake news. Remember the old adage: “Tell someone the truth and they’ll ask you for facts. Present them your facts and they’ll question your sources.” Skepticism is always healthy, but most people aren’t being skeptical, they’re adhering to their beliefs and world view rather than changing them to fit the facts. It’s usually because they want, really badly, for their world view to be right for whatever reason. This is where cognitive dissonance stems from.