Power stations get most of the attention, but they are only part of the story. Most of the world's energy is used to move people and goods and to make heat, for homes, for cooking and for industry. Cleaning up those uses is where the transition gets hardest.

Heat and motion

Heat is the overlooked giant. Heat, for buildings, cooking and industry, accounts for almost half of the world's final energy use. Much of it comes from burning gas, oil, coal and wood directly. Transport, meanwhile, runs almost entirely on oil.

A widely shared strategy is to clean up the electricity supply and then shift as much transport and heat as possible onto it. The reason is not only that electricity can come from clean sources. Electric machines waste far less energy than engines that burn fuel, so electrifying a use usually cuts the total energy it needs.

Electric vehicles

The difference is striking in cars. An electric car turns roughly three quarters or more of the energy it draws into motion, while a gasoline car turns only about a fifth to a third; the rest leaves as heat from the engine and exhaust.

Sales have risen quickly. Electric cars made up more than a fifth of new car sales worldwide in 2024, about half in China, and close to nine in ten in Norway, which exempted them from heavy car taxes. Critics raise fair points. Batteries need mined minerals, discussed in the next level. Electric cars cost more up front in many markets, and charging is hard for people without a driveway. On climate, the evidence is fairly clear: building an electric car's battery causes extra emissions at first, but over its life the car usually comes out well ahead of a gasoline car, and further ahead where the grid is clean.

Heat pumps

For buildings, the leading clean option is the heat pump, which works like a refrigerator run in reverse. The physicist William Thomson, later Lord Kelvin, described the idea in 1852. A heat pump moves heat from outside air or ground into a building rather than making it, delivering about three units of heat for each unit of electricity in typical conditions. That is why it can beat even a very efficient gas boiler. Heat pumps work in cold climates; Norway and Finland have some of the highest rates of use in the world, though efficiency drops in severe cold. They cost more to install than boilers, work best in insulated buildings, and save money only if electricity is not too expensive compared with gas.

The hard cases

Some uses resist electrification. Steel is one. In a blast furnace, coal in the form of coke is not just a fuel but a chemical ingredient that strips oxygen from iron ore. A clean alternative uses hydrogen to do that job instead. In 2021 a Swedish project called HYBRIT delivered the first steel made this way to a carmaker. Cement is another. Most of cement's carbon emissions come from heating limestone, which releases carbon dioxide from the rock itself, so even clean heat solves only part of the problem. Long-distance flying needs fuel that is light for its energy, and batteries are far too heavy; options include fuels made from plants or waste, synthetic fuels made with clean electricity, and flying less. Ocean shipping is testing fuels such as ammonia and methanol.

Efficiency and the rebound

The cheapest energy is the energy not needed, through insulation, better motors and smarter design. But efficiency has a catch that the English economist William Stanley Jevons spotted in 1865. In The Coal Question he wrote, "It is wholly a confusion of ideas to suppose that the economical use of fuel is equivalent to a diminished consumption. The very contrary is the truth." Jevons argued that more efficient use of coal would lead Britain to burn more of it, not less, because cheaper steam power would find new uses. Today this is called the rebound effect. Most studies find that rebound usually eats only part of the savings, but it means efficiency alone rarely shrinks energy use as much as engineering estimates suggest.

Worked example: Kraków gives up coal

For years Kraków, Poland, had some of the dirtiest air in Europe, much of it from tens of thousands of coal and wood stoves in homes. From September 2019 the city banned burning solid fuel for home heating and offered subsidies to replace old stoves. Imagine a family in an older house choosing a replacement. A gas boiler is cheapest to install, but it burns a fossil fuel whose price spiked in 2022. A connection to the city's district heating network is convenient where pipes reach. A heat pump costs most up front, works best after insulation, and draws power from a grid still heavily dependent on coal, though that grid is getting cleaner.

Apply the ideas. Any choice ends the smoke inside the city, which brings immediate health gains. The heat pump wins over time because of its efficiency, and it improves as the grid improves; the gas boiler locks in fossil fuel for fifteen years or more. The case shows why heat and transport change house by house, and why subsidies and information matter.