Skip to content

European Governments and regulators are responsible for defining the types of electricity generation that are considered renewable in the UK. And there are a few ways to generate green electricity at scale.

At Bulb, we’re particular about the renewable generators we buy from, and not every technology makes the cut. Here, we take a look at how our electricity is produced, and how we make decisions when it comes to sourcing green energy on behalf of our members.

We buy electricity generated from renewable sources with a low environmental impact


Illustration of an off shore wind farm

Wind turbines harness the movement of the wind to generate electricity. At Bulb, we buy power from onshore and offshore wind farms. Wind power is currently the largest renewable contribution to the UK's fuel mix – and makes up over three quarters of the electricity we supply.


Solar power uses sunlight to generate electricity. Solar panels (also called photovoltaic cells) are capable of converting light into electricity directly. And when you get lots of them together, you’ve got a solar farm. We work with plenty of these across the UK, and we also buy solar power directly from Bulb members who have installed solar panels on their property.

Low impact hydro

Hydropower harnesses the energy of falling or flowing water to create electricity. We work with small-scale plants across the UK that divert the natural course of a river. Even the smallest hydro projects can have a big impact, just ask our friend Tegwyn at the Tyn Y Cornel hydro plant in Snowdonia.

Anaerobic digestion

Gas is produced naturally when organic material – like food and farm waste – decomposes. This biogas can be captured and burned to produce electricity in exactly the same way as natural fossil gas.

Biogas produced from anaerobic digestion is roughly 50% methane and 50% carbon dioxide. Both are greenhouse gases that contribute to warming our planet. But methane has 84 times more global warming potential than CO2. So it’s less harmful for the planet to turn it into something useful – like renewable electricity – than to release it into the atmosphere.

Find out more about Bulb's fuel mix

Read about how we source our energy, or take a look at the breakdown on our fuel mix page. Explore our generator map to see the green generation sites we work with.

We don’t buy green electricity generated from sources that damage the environment

Some generation technologies are considered renewable by Ofgem, but they don't make it onto our sourcing list.


Illustration of a big pile of logs

Biomass electricity is generated by burning organic material – like wood pellets from trees. Last year, biomass made up 21% of the UK’s electricity, and most of it was generated by burning wood pellets exported from the USA and Canada. In fact, the UK is the largest importer of wood pellets in the world. The pellets are burned at power plants like Drax in Yorkshire, which used to be Europe’s largest coal plant.

Though electricity made this way is considered renewable in the UK, it’s unclear whether burning biomass produces fewer CO2 emissions than burning fossil fuels. That’s according to the government’s own research – and it’s been a heated debate for many years. Though biomass can be a sustainable form of generation, it often falls short.

At Bulb, we don’t buy electricity from biomass. We’re the only supplier we know of who won’t.

Current regulations don’t take into account the full impact of cutting down trees to create wood pellets – like the CO2 released by the soil. Biomass could have an important role in reaching net zero but only if we create tighter rules to guarantee and verify the carbon savings.

Until then, we’re not going to buy any electricity made this way.

Energy from waste and landfill gas

Illustration of a black bin bag

Energy from waste (EfW) involves burning rubbish to create steam, which drives a turbine to create electricity. You might see it called ‘Municipal Incineration of Waste.’ Most of the waste burned in the UK comes from homes. But it can be commercial waste from offices, schools and shops, too.

EfW produces CO2 and other greenhouse gas emissions. Burning waste in this way can produce toxic fumes like dioxins, which can pollute the local environment and may pose a health risk.

Landfill waste can be left to decompose naturally, which releases biogas that can be captured and burned for electricity. But household and industrial waste often contains plastics, which are produced using fossil fuels. This means it’s not possible to guarantee that EfW and landfill gas electricity are always renewable sources of energy.

Large scale hydro or pumped storage

Hydroelectricity can be generated in a few ways, but the idea is to force water through a turbine. Large-scale hydro plants do this with a system of pumps, dams and reservoirs. We consider a hydro site ‘large’ if it’s bigger than 5MW in capacity. A hydro site that size would produce enough electricity to power around 4,000 homes.

Pumped storage hydropower involves pumping water from a low reservoir up to a higher one. The water is then released at periods of high power demand, where it flows down through turbines, generating electricity. There are only four pumped storage sites in the UK today. The largest is Dinorwig Power Station in Wales.

We don’t buy electricity from large-scale hydro or pumped storage sites. This in line with our commitment to B Corp guidance. Large-scale hydro and pumped storage can cause damage to the downstream environment, which can disrupt fish populations, reduce water quality and change river sedimentology. We’d rather not upset the local wildlife, so we stick to buying electricity from small, run-of-the river hydro sites, like Tyn Y Cornel in Wales.

There are other ways to make green electricity that don't exist at scale yet

We’d be happy to buy from these sources in principle, as long as their impact on the environment tallied with our high standards.

Wave and tidal power

These types of hydropower use the movement of the sea to generate electricity. Kinetic wave energy caused by weather systems can be captured offshore or on the coast before being converted into power using buoys and turbines. Tidal energy generation uses a system of sluices and tidal fences to harness currents and channel water through a turbine as the sea level changes.


Geothermal power uses underground heat to create electricity. Geothermal plants harness or create steam using the heat from molten rock under the earth's surface, and then force this steam through a turbine to generate electricity. They can also use water that's been warmed underground to provide heating and hot water directly to homes and businesses.