Bjorn’s Corner: Sustainable Air Transport. Part 45. eVTOL, how green?

By Bjorn Fehrm

November 11, 2022, ©. Leeham News: We have spent some 50 articles going through the new air transport category, eVTOL, or electrically propelled Vertical TakeOff and Landing vehicles.

They promise to replace the helicopter for local air transport above congested cities and highways.

The question is now: How do eVTOLs fit in sustainable air transport? Are they a green way of starting a flight journey, and how does it compare to alternative transports?

Figure 1. The World’s energy consumption and sources. Source: World in Data and BP.

How green is eVTOL

eVTOL OEMs push the green credentials of their products. But how green is this mode of transport? Some proponents say it can compete with chauffeur-driven cars like Uber transport.

We have the typical energy consumption per mile or km for our eVTOLS. We consumed 50kWh for a 25nm leg from the city center to the local airport. It was with four passengers and the pilot. It also included takeoff and landing procedures that does not count for distance.

If we reduce the load factor to the level Joby assumes in their calculations, 2.3 passengers on average, we get a lighter eVTOL and end up with a consumption of 42kWh for the trip. It means we consume 18.3 kWh per passenger to move them 25nm, or 0.73kWh/nm, 0.39kWh/km, or 0.63kWh/mile.

How does this compare to other means of transport?

We use Wikipedia to get the values of energy used per passenger km traveled.

If the passenger takes an airport shuttle train, the consumption is about 0.10kWh/km or four times lower per passenger km than an eVTOL. This value is for “Urban rail,” which contains a lot of stops and goes.  An airport shuttle that uses a more direct run might have a lower value, closer to a local train of 0.05kWh/km.

A turboprop like an ATR 72-600 with a 75% load factor has the same energy consumption per passenger and km (0.10kWh/km) on its typical feeder routes of 300nm. The intercity Boeing 737 MAX or Airbus A320neo would consume 0.15kWh per passenger and km. You pay for the higher speed with higher energy consumption.

The gasoline-powered car is an energy hog, as discussed before. It consumes about 50% more energy than the eVTOL at 0.60 kWh/km and transported person, but if we instead use an electric car, we are at 0.15 kWh/km or 2.6 times lower than if the passenger is flown in an eVTOL. This is when we count, on average, 1.4 people in the car during daily use.


Figure 1 shows the energy consumption by type over the last 200 years. Over the last 50 years, our energy consumption has exploded, and the main sources of energy are carbon-based; coal, oil, and natural gas. If a transport system uses electric energy for its consumption today and tomorrow, we can’t say this electricity was produced by the tiny green sources we have. Thus we have an energy consumption problem and not enough green sources to replace the carbon-based ones running the world right now.

That a transport uses electric energy as the storage and propulsion source doesn’t qualify it as green. It simplifies the switch to green energy but doesn’t change the label. The source of the energy does.

If we add a new transportation concept that consumes 2.6 to four times more energy than an electric car or a shuttle train, should it be called a sustainable way of transporting people? Just because its energy consumption is based on electric energy? In the large scheme of things, we need to lower our energy consumption per person, not increase it.

I, therefore, think that part of the eVTOL pitch shall be declared invalid.

eVTOLs will be a more convenient way in certain large cities to get to an airport and replace helicopter services, but that’s for the privileged few or business travelers using such transports today. It’s certainly not a means to lower our energy consumption. The average Joe, with his family, will continue to take the airport train at a four times lower energy consumption.

18 Comments on “Bjorn’s Corner: Sustainable Air Transport. Part 45. eVTOL, how green?

  1. “If a transport system uses electric energy for its consumption today and tomorrow, we can’t say this electricity was produced by the tiny green sources we have. ”

    But everybody is marketing just that.

    Thanks Bjorn for the article, back to the sources. Now we need to get those realities between the ears of all politicians and people working, financing and promoting the by now huge industries for electric vehicles.

    “It’s difficult to get a man to understand something when his salary depends on not understanding it.” (U. Sinclair ~1934)

    My personal opinion is we need to drastically rationalize our energy consumption & invest hugely in hydro energy & nuclear power plants. Whether we like that idea or not. Otherwise the electrification of our societies is only hiding our real energy source problem.

  2. One advantage is the direct routing, hence compared to a car fewer miles are travelled to the airport from the city center. Some countries have a big % of electricity produced that do not create emissions at the powerplants. Like Norway, Denmark, Sweden, France, Canada, Brazil. Airports are normally wide open and suitable for wind power if allowed designs become certified by FAA/EASA.

  3. Given that according to the article, eVTOL’s are supposed to replace helicopters, it would be interesting to compare their energy consumption with helicopters rather than trains, planes and automobiles.

    I suspect they would fare considerably better in that comparison.

    • My thoughts exactly. A comparison with something small like a Robinson 44, ans something more likely to be used by the wealthy (a larger Bell or Eurocopter).

    • Noice and emisions are important comparisons also. The Robinson R44 burning 100LL vs. the electrical “The Tier 1 Robinson R44 electric helicopter (N3115T)” in its first iteration would be interesting reading.

  4. If I drive to the airport, I leave my car at the airport. If I catch an eVTOL it has to do a round trip each time. It is unlikely to get another set of passengers on a ‘positioning’ leg coming to pick me up, therefore it covers double the distance. That surely makes it even less environmentally friendly?

    • Thats why an optimizing software is needed like for taxi fleets or truck fleets to optimize revenue and operations. I.e. max revenue and minimun non-revenue flying. There are lots of express freight to/from airports to city that UAM’s can pick profitable items, like cold freight vaccine or similar. Once they are certified the market will look for applications that generate profit.

  5. This analysis is making several unfair comparisons. First, it refers to renewables as “tiny”. By 2025 non-carbon electricity generation is expected to be 50% in the US and is already beyond that in some areas. Second, the comparisons to future vehicles or fixed wing aircraft are unfair; the claims are versus current forms of transportation. Last, eVTOLs are not competing against public transportation., rather against luxury terrestrial vehicles or, as another commenter mentioned, helicopters.

    • @analyst – right. I charge my Ford Focus electric with 5 kW solar panels on my house. Bjorn’s figure for EVs is just what I get; .15 kWH/km/passenger. Again – much more energy efficient than an electric helicopter, and arguably green from end to end.

      I suppose the base for electric helicopters could be surrounded by solar panels. That might be a good idea with or without electric helicopters.

    • US renewable energy production was 24% in first half of 2022, according to energy information Agency EIA

      Which agency is saying it will double in 3 years time?

      Yet again the make believe data comes into play like almost all the other evtol claims

      • I didn’t say renewables, I said non-carbon. That includes nuclear. Also, 24% is not tiny and it’s growing very fast. Please – this is not politics, it’s business.

      • It seems for the US 12% is renewable energy. Of which 40% are biofuels. Biofuels are increasing questioned if they deserve the renewable lable or not.

        Still positive, yet incomplete or confusing information is used to influence perceptions, make people feel good, make them hopefull, forgiving.

        Saying electricity while you mean energy, mix non carbon & renewable, mixing energy sources and storage, pulling forward future wins, pushing out great promises, unjustified Techno-Optimism. It’s depressing.

        One of the (very few) advantages of the current energy crisis might be people better seeing realities. Next to the massive communication from bodies that prove less independent and objective than they look. From both sides.

        • Your link is total energy consumption, which includes auto, truck, & bus transportation, industrial uses, and residential heating. Do you realize how sanctimonious you sound especially when you are the one using misleading information? We’re trying to discuss the sources of electricity generation. If you all were not so politically motivated in making your points you might be more careful analyzing data instead of cherry-picking information that fits your bias.

          • Isolating electricity generation from energy consumption is useless. Car go from oil to electricity.

            House warming from gas to electricity. Mind & word games that don’t support real progress.

            Better take into account the primairy energy sources, like in the OP.

            P.S. in general trying to put people into corners to then dismiss them I see as old school and very unimpressive.

  6. Some comments to this article I feel are missing the point and hostile to the author. If you can measure something and express it in numbers then you know something about it.
    This is what Bjorn has done. These negative comments are not proving his analysis incorrect and are arm waving and emotion.

    My takeaway from this article is that, and well stated in the summary, as of now and in the near-term future the push to battery powered cars/trucks/aircraft by the green energy bandwagon is not attainable and is not attacking the tall pole standing in the way of a solution.

    He doesn’t say it’s a bad idea.

    Energy is neither created nor destroyed it is only converted from one form to another. Presently 87% of the
    The energy used in the world is derived from fossil fuels, that’s the problem. Battery powered cars/trucks/aircraft
    don’t solve that.

    I am all for green energy and working on a solution. But how do you ban the use of gas/diesel cars by 2035 as has been done by several states if you don’t know how to do it? Do you just hope for a miracle? Hoping for something to happen in the future is usually not a good development strategy.

    • “…the green energy bandwagon is not attainable…”

      The green movement is built upon questionable assumptions, faulty logic, highly idealized scenarios/proposals and outright bigotry. Unfortunately, anyone who tries to point this out runs the risk of being casually dismissed as a “climate denialist”.

      There are major obstacles blocking the path of any form of energy transition, and very few people are talking about them in a realistic manner. There seems to be a simplistic attitude of “we need to do this, so we’ll succeed”.

      Meanwhile, activist GenZ dropouts are gluing themselves to famous paintings all over Europe — as if that’s going to solve anything.

  7. Operator should take into consideration the size of the landing fields and the energy required to make and use them. Since the VTOL is unstable upon takeoff and landing especially in gusty areas, they need significantly more spacing than taxies. A football field to serve just 100 people per hour?

    Just can’t imagine enough free space in pricey downtowns where the wind is turbulent around tall buildings. Making landing field in Suburbia is pointless. Who will use it?

    Taxies can line up with bumper to bumper spacing in multiple rows.

    Every VTOL operation requires huge landing fields as there is not much energy reserve left at the end of the journey. Recharging/refueling them also requires lots of space. The recharge takes forever so the expensive space is occupied for at least half an hour. If you recharge the battery fast then it degrades fast. Battery swap will not happen, between the loose, deforming contact there is a nice fire hazard. Besides that the contact life will be misrable. If the contact is secured with nuts, then someone needs to touch high voltage, high amp contacts upon each swap (in every 5 minutes or so), also not a life insurance.

    Any monorail or automated shuttle car from downtown to the terminal on dedicated track will beat the small VTOLS with much less hazard, works year round and in all weather.

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