Where electricity comes from today

The UK generates electricity from a mix of sources. Gas-fired power stations still do a lot of the heavy lifting, especially when the weather is calm. Nuclear contributes a steady baseline. Wind, both onshore and offshore, supplies a large and growing share. Solar contributes too, mostly in summer and mostly from large farms and rooftops. Small amounts come from hydro, biomass, and imports through undersea cables from France, Norway, Belgium, and the Netherlands.

The balance changes hour by hour. On a windy afternoon in March, wind can supply more than half of all UK electricity. On a still evening in January, it can be below five percent. The grid has to juggle this constantly.

Why we are changing the mix

Three reasons, usually stacked together.

First, climate. Burning fossil fuels releases carbon dioxide, which warms the atmosphere. Countries including the UK have committed, legally, to reducing net emissions to zero by around 2050. You cannot do that while generating most of your electricity from gas.

Second, air quality and health. Coal plants and, to a lesser extent, gas plants release other pollutants that affect local air. Cleaner generation reduces that burden.

Third, energy security. Fossil fuels are traded on global markets. When those markets go haywire, as they did in 2022, bills go up and governments scramble. Generating electricity from domestic wind and sun does not remove that exposure entirely, because the supply chains and the grid are still global, but it reduces one leg of it.

Why wind and solar lead the new build

Wind and solar have two features that changed the picture. They are now genuinely cheap to build, in most places cheaper than new gas or coal plants per unit of electricity produced. And they scale. Once you have figured out how to build one wind turbine, you can build a thousand.

They also have a feature that makes life harder. They are variable. The wind does not blow on demand, and the sun does not shine at night. So a grid with a lot of wind and solar needs other things alongside, storage, flexible backup plants, demand that can shift, and strong interconnectors to neighbours. The engineering question is not whether this can work. It already does, in several countries. The question is how fast, and at what cost.

Why offshore wind specifically

Onshore wind works well, but there is only so much land, and turbines near homes are politically contested. Offshore wind takes the same idea and puts it in a place with more space, stronger winds, and steadier winds. A turbine at sea typically generates electricity about half the time it is in operation, compared to about a third for onshore. The turbines are also much bigger. Modern ones have blades longer than a football pitch.

The UK has a useful natural advantage. Shallow seas on the east coast and strong winds in the North Sea make it one of the best offshore wind environments in the world. That is why offshore wind has grown here faster than almost anywhere else, and why it matters so much to the UK version of the energy transition.

How a wind farm actually works

A turbine is, at heart, a big fan running in reverse. Wind pushes the blades, the blades turn a shaft, the shaft drives a generator, and the generator produces electricity. That electricity travels down a cable inside the turbine tower, across the seabed through a buried cable, into an offshore substation, and from there to shore.

A wind farm is a cluster of those turbines, often dozens or hundreds, connected to one or two offshore substations. The substations bundle the electricity up to high voltage for the long journey to shore. Onshore, another substation steps the voltage back down and feeds it into the regional grid, which carries it to homes, factories, and everywhere else.

The whole thing is designed to run for twenty-five to thirty years, mostly unattended, in a very hostile environment. Getting to and maintaining turbines in a six metre swell is its own specialist industry.

Questions people actually ask

Why do turbines stop turning when it is windy?

Usually not because they are broken. The most common reason is that the grid cannot take the electricity they would produce. If there is already more electricity in the system than there is demand, and the cables out of the area are full, the grid operator pays the wind farm to switch off. This is called curtailment. It is not unique to wind. Gas plants get turned down too. The difference is that a wind turbine sitting still in a gale is a lot more visible than a gas turbine doing the same thing.

How much electricity does one turbine make?

A large modern offshore turbine can generate enough electricity in a year to supply several thousand homes. The exact number depends on the turbine size and the local wind conditions. A fifteen megawatt turbine at a windy offshore site can produce enough in a year to cover the electricity, though not the heating, of somewhere around fifteen to eighteen thousand average UK homes.

Are turbines bad for birds?

Some birds die from collisions with turbines. The totals are small compared to birds killed by cats, windows, or cars, but the question is not just about totals. Specific species, particularly seabirds that forage at turbine height, can be disproportionately affected. That is why offshore wind farms go through long environmental assessments before being built, and why siting matters. It is a real concern, not one that has been dismissed, but not the defining issue that the strongest critics suggest.

How long do turbines last?

Most are designed for twenty-five to thirty years. At that point they are either repowered, meaning the turbines are replaced with newer larger ones on the existing foundations, or decommissioned. The first generation of offshore wind farms in the UK is only now starting to reach that decision point, so the answer to what happens next is being worked out in real time.

Is the energy transition actually happening?

Yes, and no. Measured by capacity added each year, wind and solar are now the default new-build for electricity in most of the world. Measured by the share of total global energy still coming from fossil fuels, we have barely moved the needle. Both things are true at once. The transition is underway, it is faster than it was ten years ago, and it is still slower than what the climate targets require.