Using energy: food, materials, mobility and buildings: Moving people and goods

4.1 Cars move mostly themselves, which is why weight and drivetrain matter

The engine of the Ford Model T weighed about 12 grams for every watt it produced. A modern car engine weighs about 1 gram per watt. That is a twelvefold gain in engineering. But cars used the gain to grow. Average engine power in the United States rose more than elevenfold to about 170 kilowatts, and the average American light vehicle now weighs over 1,800 kilograms, about three times the Model T.

Smil's favourite ratio is vehicle weight to payload. Most American commuters drive alone. An 1,800 kilogram SUV carrying a 70 kilogram driver moves about 26 kilograms of machine for every kilogram of person. A bicycle's ratio is about 0.1. A full bus or train does far better than any car. Much of the energy in personal transport goes into accelerating and braking the vehicle itself, and into pushing air out of the way.

The drivetrain decides how much of the fuel ends up as motion. A petrol engine in mixed driving turns perhaps 20 to 30% of its fuel into work at the crankshaft, and less after the gearbox. The rest heats the radiator and the exhaust. An electric drivetrain turns about 80 to 90% of the battery's energy into motion and recovers some of the braking energy. This is the main reason electric cars use about a third of the final energy of petrol cars for the same trip.

Heavier cars cut into that advantage. A large electric SUV needs a bigger battery, which adds weight, which needs more energy. Smil's point stands for both drivetrains: lighter vehicles, carrying more people, are the cheapest efficiency gain of all.

• Smil, Numbers Don't Lie (2020) · via Smil Mastery Course, M14 'Moving people: cars, jets and flight safety'
• Smil, Energy: A Beginner's Guide (2006) · via Smil Mastery Course, M1 'Conservation and efficiency'

4.2 Electric cars are now a quarter of global sales, led by China

Smil reminds readers that the electric car has been 'the future' since about 1900, when electric taxis worked the streets of New York. The difference now is cheap lithium-ion batteries, and the numbers have finally moved.

According to the IEA's Global EV Outlook 2026, more than 20 million electric cars were sold worldwide in 2025, about one in four new cars. China dominates: electric cars took nearly 55% of its sales, and the country had an estimated 44 million on the road, about 13% of its car fleet. Europe reached about 28% of sales. The United States was just under 10%. India sold about 165,000 electric cars, up 75% on the year but still only around 4% of its market, about 60% of them made by Tata and Mahindra. Across the world, electric vehicles still make up only about 5% of the car stock, because fleets turn over slowly.

The IEA expects about 23 million electric car sales in 2026, around 28% of the market. Electric cars displaced about 1.2 million barrels of oil a day in 2025, and all electric vehicles together about 1.7 million. Price is the key driver. In China about 70% of battery electric cars sold in 2025 were already cheaper than the average conventional car.

For India the more important story may be smaller vehicles. Electric three-wheelers already exceed a quarter of sales worldwide, and electric two-wheeler sales in India grew strongly in early 2026. Electric trucks are also arriving: they reached about 9% of truck sales globally in 2025, and about one in four in China.

• IEA, Global EV Outlook 2026: Executive summary, International Energy Agency, 2026 · web
• IEA, Global EV Outlook 2026: Trends in electric cars, International Energy Agency, 2026 · web
• Smil, Energy Myths and Realities (2010) · via Smil Mastery Course, M9 'Energy myths and realities'

4.3 Jets and ships need dense fuels, which is why they are the hardest to electrify

A long-haul aircraft must carry its energy into the sky and keep it there for half a day. Weight is everything. Jet kerosene packs about 42.8 megajoules per kilogram, stays liquid down to minus 47 degrees Celsius, and is cheap and relatively safe to handle. The best lithium-ion cells store under 1 megajoule per kilogram. Even allowing for the higher efficiency of electric motors, batteries for an intercontinental airliner would weigh many times more than the aircraft could lift. Smil calls battery-powered intercontinental jets science fiction for the foreseeable future. Aviation produces about 2% of global CO₂ and around 12% of transport's, and its most realistic substitutes are drop-in liquid fuels made from biomass or from hydrogen and captured CO₂, both of which are expensive today.

Ships face a milder version of the same problem. Global trade moves mostly by sea, in tankers, bulk carriers and container ships driven by huge two-stroke diesel engines that can exceed 80 megawatts and convert about half of their fuel energy into work, among the most efficient engines ever built. Smil notes that these vessels often carry no backup engine at all, a sign of how reliable the diesel has become.

Per tonne carried over a kilometre, an ocean ship uses something like a tenth to a twentieth of the energy of a lorry and about a hundredth of an air freighter. That is why shipping can move most of world trade by volume while using only a few per cent of global energy. The challenge is that ships sail for weeks between ports, so they need a fuel dense enough to carry. Candidates include ammonia, methanol and liquefied gas.

• Smil, Numbers Don't Lie (2020) · via Smil Mastery Course, M14 'Moving people: cars, jets and flight safety'
• Smil, Two Prime Movers of Globalization: The History and Impact of Diesel Engines and Gas Turbines (2010) · via Smil Mastery Course, M14 'Moving people: cars, jets and flight safety'
• Krammer, P. et al., 'Energy intensity of freight transport modes', npj Sustainable Mobility and Transport (2025), Table 1 · web

See it in the table

Check your understanding

Why do electric cars use roughly a third of the final energy of petrol cars for the same trip?

What is the main physical obstacle to battery-powered long-haul aircraft?

In 2025, roughly what share of new cars sold worldwide were electric?