Who were the most sustainable energy suppliers for 2024 in the UK?

TL;DR

• There are 21 energy suppliers in the UK but only three earned top rankings in the Which? rundown of sustainable energy suppliers: Octopus Energy, Ecotricity, and Good Energy.

• Each of these suppliers goes above and beyond when it comes to sustainability, rather than simply buying renewable energy guarantees of origin (REGOs) certificates.

• Octopus Energy is one of Europe’s largest investors in renewable power, Ecotricity sells its own green gas, and Good Energy is a certified B Corp supporting community generation.

• At the other end of the scale, the lowest scoring energy suppliers include Outfox the Market, E (Gas & Electricity), and Utility Warehouse, all of which focus on price rather than sustainability.

• For consumers to contribute to the energy transition, renewable energy must be made more affordable and the reality of green tariffs must be understood so that the public can make fully informed decisions.

The detail

With the UK’s net zero target now just 25 years away, the country’s energy landscape needs to undergo rapid transformation. While the measures being taken at a legislative and industrial level will likely have the greatest impact on the UK’s emissions, everyday consumers still have a role to play.

The cost-of-living crisis of the past two years has understandably put pricing at the top of most households’ priority list, but that’s not to say that the environmental credentials of their energy supplier aren’t also an important consideration. Public awareness of the impact of climate change has increased in recent years and more suppliers than ever before are offering green tariffs with 100% renewable energy.

The evolving energy landscape

But are these sustainable tariffs really benefitting the environment and driving the energy transition forward?

There are currently 21 energy suppliers active in the UK’s domestic gas and electricity market. Traditionally, the sector was dominated by the so-called Big Six – SSE, British Gas, EDF Energy, E.ON, npower, and Scottish Power – but the industry has undergone a significant shift, switching suppliers has become much easier, and emerging players have gained more of a foothold. In fact, Octopus Energy now has the most significant market share, supplying 23.7% of UK households.

Each of these 21 suppliers takes a different approach to sustainability and renewable energy. Many have made green tariffs a core part of their offering while others have focused on keeping costs low rather than prioritising improving their environmental credentials.

When looking to determine who were the most sustainable energy suppliers in 2024, it’s important to consider the metrics that matter. The first point to note is that it’s impossible for any domestic consumer to achieve net zero if they are buying their energy from a supplier.

No matter the supplier, as the UK’s electricity operates on a shared system, all energy consumed will have the same carbon footprint: 0.26 21kg CO2e per kWh. Even so, that doesn’t mean consumers should forego personal responsibility. By becoming informed about the measures that make a real difference, they can make the best possible choices for their household and the planet at large.

The metrics that matter most

So, what should consumers be paying attention to?

As well as supplying more energy from renewable sources than the average fuel mix, the most sustainable companies also buy their renewable power directly from generators. They score extra points for generating their own renewable power. Unfortunately, there are several UK suppliers that claim sustainable credentials but aren’t actually involved in generating or buying any renewable energy themselves. Instead, they simply buy the same amount of renewable energy certificates to match the energy their consumers purchase.

To advertise a tariff as providing 100% renewable electricity, the energy supplier must purchase enough of these certificates, known as renewable energy guarantees of origin (REGOs), to offset their customers’ consumption. However, this doesn’t mean that the company won’t still earn the majority of its profits from fossil fuels or stop the money you pay in your bills going to support the sale of more coal, oil, and gas.

The most sustainable energy companies should also encourage their customers to make more environmentally friendly choices. This might include introducing tariffs or technology-driven products that encourage customers to use energy off-peak, live more efficiently, and pay attention to their carbon emissions. They may also support their customers by installing heat pumps and solar panels.

Of course, the company’s Scope 1, 2, and 3 emissions should also be kept as low as possible and suppliers may choose to help offset the harm caused through energy generation by making charitable donations or planting trees.

It’s also worth keeping in mind that for a company to make an environmental claim about a tariff, they should:

• Show that any environmental gain is due to the customer choosing that tariff

• Publish the fuel mix and information about the environmental benefit of the tariff

• Be able to prove where its renewable energy has come from

The top three

Who were the UK’s most sustainable energy suppliers in 2024? The top three spots, according to Which?, went to Octopus Energy, Ecotricity, and Good Energy.

The good news is that Octopus Energy is not only the leading energy supplier in the UK, but it’s also the most sustainable. Which? highlighted the fact that it generates its own renewable power from solar and wind as well as buying direct from generators, its extensive range of flexible time-of-use tariffs, and the low-carbon technology it supplies to its customers.

The company itself claims to be one of Europe’s largest investors in renewable power. It operates £6 billion worth of renewable generation, which would be enough to power four million homes. That’s not all; it also buys from 700 green energy producers in the UK and has paid over 100,000 people for solar power generated at home since April 2019. Octopus customers have generated an impressive 1.16 billion kWh and the company has offset more than one million tonnes of carbon between 2018 and 2023.

One of the main differentiators of Octopus Energy is that it manages and produces its own renewable energy. It is responsible for 4 GW of renewable electricity across 240 large-scale energy projects that span 10 countries. It also continues to invest in sustainable projects, putting £10 million towards building the UK’s only low-carbon heat research and development centre and committing £15 billion to fund offshore wind. In the coming years, it hopes to expand its European green generation projects to 20 GW, which could power 15 million homes.

Ecotricity has been operating since 1995 and generates energy that is certified green. It sources electricity from wind and solar and is one of four companies that sells its own green gas (biomethane). This is a mix of carbon-neutralised natural gas and sustainable gas that is produced using grass, and the carbon that is produced when this gas is used is then reabsorbed as the grass grows back. It hopes to eventually generate enough green gas to power every home and business in the UK without taking any land away from the food production industry.

Investment is another area where Ecotricity shines. Since 1995, it has built 24 wind parks and recently completed two new solar power plants. It also operates a ‘bills into mills’ policy where profits are invested into constructing more renewable generation.

Rounding out the top three, Good Energy is the only home energy supplier in the UK to be a Certified B Corp. Founded 25 years ago, it prides itself on supplying truly renewable energy and buys directly from over 2000 renewable generators in Britain. It also pays homes and businesses for the renewable energy they supply to the grid so that it has enough available to cover its customers’ entire usage. It is also the largest voluntary administrator of the Feed in Tariff and helps encourage at-home and community generation by installing solar panels, home batteries, and heat pumps.

Cost vs. climate

At the other end of the scale, three companies were called out as scoring lowest on the Which? Assessment: Outfox the Market, E (Gas & Electricity), and Utility Warehouse. These providers stand out as companies targeting the low-cost consumer with their messaging and commitments targeted towards cost-saving measures rather than sustainability.

With the Labour Government’s push to prioritise secure renewable energy, embodied by the launch of GB Energy, it’s likely that UK energy suppliers will continue to have their sustainable credentials put under scrutiny. However, it’s important that the Government and consumers put pressure on suppliers to focus on the metrics that matter rather than offering supposedly ‘green’ tariffs but simply buying enough certificates to back up their marketing claims.

In the ongoing tension between economy and environment, it’s essential that renewable energy options become just as affordable as traditional fossil fuels for domestic consumers. When forced to make a decision between saving money and saving the planet, it’s understandable that many consumers will be more convinced by the opportunity to reduce their costs than cut their carbon impact.

It all starts with the suppliers. Not only must they commit to sustainable tariffs that include genuine investment in renewable energy generation, but they should also continue to offer customers the means to take part in the energy transition. Whether that’s generating their own solar or wind power or switching traditional boilers for heat pumps, providing these services, and incentivising them by offering generous terms for any energy generated and added to the grid, could help even those on the lowest incomes see the benefit in going green.

— Lew 👋

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The Transition’s work is provided for informational purposes only and should not be construed as advice in any capacity. Always do your own research.