Electrical Energy

Electrical energy is energy carried by the flow of electric charge through wires and circuits. It is one of the most useful forms of energy ever discovered, because it can be moved easily over long distances and converted to almost any other form (light, heat, motion, sound) at the press of a switch. Almost every modern convenience uses electrical energy. Lights, fridges, computers, phones, electric cars, hospitals, factories, trains, traffic lights and even pacemakers in some peoples chests all run on it.

  • What it isEnergy of flowing electric chargeUsually electrons in wires
  • UnitJoules (J) or kilowatt-hours (kWh)1 kWh = 3.6 million joules
  • PowerP = V x IVoltage times current
  • UK home useAbout 8 kWh per dayAverage household
  • Electricity made byGenerators, solar cells, batteriesVarious sources
  • Converted toLight, heat, motion, soundIn countless devices

How electrical energy is carried

Electrical energy is carried by moving electric charge. In wires, this is the flow of electrons through metal. The amount of energy carried depends on two things:

  • The voltage (how strongly the charges are pushed). Measured in volts (V).
  • The current (how many charges per second). Measured in amperes (A).

The total electrical power (energy per second) is voltage times current: P = V x I, measured in watts (W).

A 60-watt light bulb plugged into UK mains (230 V) draws about 0.26 amps and uses 60 joules of energy per second. A kettle (3,000 W) draws about 13 amps.

How electrical energy is generated

The biggest sources of electrical energy in the UK and the world:

  • Gas power stations: burn natural gas to make steam, which spins turbines connected to generators.
  • Wind farms: wind spins turbines directly. About 30 per cent of UK electricity in 2024.
  • Solar farms: photovoltaic cells convert sunlight directly to electricity. Around 5 per cent of UK electricity.
  • Nuclear power stations: heat from nuclear reactions makes steam, spins turbines. Around 15 per cent of UK electricity.
  • Hydroelectric: falling water turns turbines. Small share in the UK; huge in places like Norway and Brazil.
  • Coal: now phased out in the UK, but still major in some countries.
  • Biomass: burning wood pellets, agricultural waste, methane from rubbish.
Fact The UK used about 290 terawatt-hours of electricity in 2024. That is 290 billion kWh. The biggest single user was industry (around a third), followed by homes (about a third) and commercial buildings (about a quarter). The rest is rail, road infrastructure and lighting. Demand peaks in winter evenings and falls in the middle of the night.

How electricity reaches your home

Electricity in the UK goes through three layers before reaching you:

  1. Generation: power stations and wind farms create the electricity.
  2. Transmission: high-voltage cables (up to 400,000 V) carry electricity long distances with low losses. The very high voltage is more efficient because, at the same power, higher voltage means lower current, and lower current means less heating loss in the wires.
  3. Distribution: at substations near towns, transformers step the voltage back down (to 11,000 V, then 230 V) for safe use in homes.

This system, called the National Grid, links the whole country into one connected network. If one power station fails, others can take over. Demand and supply have to be balanced minute by minute to prevent blackouts or surges.

How electrical energy becomes useful

Electrical energy can be converted to many other forms:

  • Light: LEDs, fluorescent tubes, screens, traditional bulbs.
  • Heat: electric heaters, kettles, ovens, hair dryers.
  • Motion (kinetic energy): electric motors in fans, washing machines, lifts, electric cars.
  • Sound: speakers, headphones, doorbells.
  • Chemical energy: charging a battery, electroplating, electrolysis.
  • Information: computers, smartphones, the entire internet.
Did you know? Your brain works on electrical energy. Neurons (nerve cells) send signals as tiny electrical pulses, like a tiny battery firing thousands of times per second. The total power used by your brain is about 20 watts, similar to a dim light bulb. Despite using such a small amount of power, the human brain can do things that no supercomputer can match.

Measuring electricity use

Most homes measure electricity in kilowatt-hours (kWh). One kWh is the energy used by a 1,000-watt device running for 1 hour.

  • Boiling a kettle (3 kW for 4 minutes): 0.2 kWh.
  • Running a 100 W TV for an evening (4 hours): 0.4 kWh.
  • Charging a phone overnight (about 10 W for 8 hours): 0.08 kWh.
  • Running a 2 kW oven for an hour: 2 kWh.
  • A typical UK home uses around 8-10 kWh per day on average.

Saving electrical energy

Cutting electricity use helps the planet and your bills. Some easy wins:

  • Switch to LED light bulbs (around 80 per cent less power than old incandescent bulbs).
  • Turn off lights and appliances when not in use.
  • Use a kettle only with as much water as you need.
  • Wash clothes on a 30-degree cycle instead of 60.
  • Choose energy-efficient appliances (A or higher rating).
  • Use timers or smart thermostats to heat only when needed.
Try this Find your electricity meter at home (with adult help). Note the reading. Wait one full day, then read it again. The difference is your homes electricity use for that day. Compare it to the average (8-10 kWh per day). Then try turning everything off except the fridge and lights for an hour and see how the meter slows down. You will get a sense of which devices are big energy users.
Deeper dive: the UKs amazing journey from coal to wind

For most of the 20th century, the UKs electricity came overwhelmingly from coal. In 1990, coal generated 65 per cent of UK electricity. Coal mines employed hundreds of thousands of people. Coal-fired power stations dominated the landscape from Yorkshire to Wales.

That has now changed completely. In October 2024, the UKs last coal-fired power station, Ratcliffe-on-Soar in Nottinghamshire, was closed. The UK became the first major economy to eliminate coal from its electricity mix, ending 142 years of coal-fired electricity since the worlds first such plant opened in 1882.

What replaced coal? Mostly two things:

  • Gas: cleaner-burning natural gas, mostly from the North Sea, took over the bulk of generation in the 1990s and 2000s.
  • Renewables: especially wind power. The UK is one of the windiest countries in Europe and has built thousands of onshore and offshore wind turbines. The biggest are at sea (offshore wind), where the wind is steadier and the turbines are out of sight from land.

By 2024, around 30 per cent of UK electricity came from wind, 5 per cent from solar, 15 per cent from nuclear, 35 per cent from gas and the rest from various other sources. Carbon emissions from electricity generation have fallen by more than 80 per cent since 1990.

The next big challenges are:

  • Storing renewable energy for when the wind is calm and the sun is down (batteries, pumped hydro, hydrogen).
  • Switching heating from gas boilers to electric heat pumps.
  • Switching transport from petrol and diesel to electric (which means a LOT more demand on the grid).
  • Building enough new wind, solar and nuclear to triple the electricity supply by 2050.

The story of UK electricity is still being written, and your generation will probably see even bigger changes than your parents did.

For more, see what is electricity and renewable vs non-renewable energy.