Rising energy demand

1. Energy demand across the world has risen steadily for more than a century and is still rising.
2. One cause is population growth, since every extra person needs energy for food, warmth, light and travel.
3. A second cause is economic development, because as countries industrialise, more people buy cars, fridges, air conditioners and phones.
4. Energy use per person is far higher in wealthy countries such as the UK than in many developing countries, but demand is now growing fastest in developing countries.
5. Fossil fuels still supply most of the world's energy, because they are reliable, the technology already exists and many countries have their own reserves.
6. The UK bucks the global trend, as its total electricity demand has fallen since the mid-2000s.
7. That fall is explained by more energy-efficient appliances, LED lighting, better home insulation and the decline of heavy industry such as steelmaking.

Daily and seasonal patterns

1. Electricity demand follows a pattern that repeats every day, and a second pattern that repeats every year.
2. Demand is lowest in the early hours of the morning, when most people are asleep and most businesses are closed.
3. It rises quickly from about 6 am as people wake up, switch on kettles and lights, and travel to work and school.
4. Peak demand normally comes in the early evening, when people arrive home, cook meals and turn on lights, televisions and heating.
5. Demand is higher in winter than in summer, because evenings are darker and more homes use electric heating.
6. Electricity cannot easily be stored in large amounts, so power stations must match the supply to the demand second by second.
7. Nuclear power stations provide a steady base load, because they run best at a constant output and take hours to change it.
8. Gas-fired power stations and hydroelectric stations cover the peaks, because they can raise their output within minutes.
9. Pumped storage stations such as Dinorwig in Snowdonia pump water uphill when demand is low and release it through turbines within seconds when demand peaks.
10. Solar output peaks around midday in summer, which does not match the winter evening peak, so other resources must fill the gap.

Changes in the UK over time

1. In 1990 about two-thirds of the UK's electricity was generated from coal.
2. During the 1990s, many new gas-fired power stations were built, because North Sea gas was cheap and these stations were quicker to build and released less carbon dioxide than coal.
3. Coal use fell sharply during the 2010s as the government added a cost to carbon emissions and tightened air pollution rules, and the last coal power station closed in 2024.
4. The share of electricity from renewable resources grew from only a few per cent in 2000 to around half by the mid-2020s, with wind now the largest single contributor.
5. Renewables grew because the cost of wind turbines and solar panels fell dramatically and because the UK made a legal commitment to reach net zero carbon emissions by 2050.
6. Nuclear power has supplied a smaller share in recent years as older reactors reached the end of their working lives, although a new station, Hinkley Point C, is being built in Somerset.
7. In transport, oil still supplies most of the energy used, but sales of electric cars are rising each year.
8. In heating, most UK homes still burn natural gas, but electric heat pumps are slowly being installed in their place.

Reasons behind the trends

1. Cost: a resource is used more when it becomes cheaper than its rivals, which is why gas replaced coal and wind is now replacing gas.
2. Availability: countries use resources they have locally, so Norway generates almost all its electricity from hydroelectricity because it has many steep, wet valleys.
3. Environmental concern: worries about climate change and air pollution have pushed countries away from coal and towards low-carbon resources.
4. Government policy: taxes on carbon, subsidies for renewables and targets for cutting emissions all shift the mix of resources.
5. Technology: larger offshore turbines, cheaper solar cells and large batteries have made renewable resources more practical.
6. Security of supply: when gas prices rose steeply in 2022 after Russia invaded Ukraine, many countries sped up plans to depend less on imported gas.
7. Reliability: however cheap wind and solar become, a country still needs some resources that can generate on a calm, dark evening.