While many people prioritise cost when it comes to choosing an energy supplier, customer service is another key factor when deciding which is the best energy provider for you. In order to identify the best and worst energy providers, we've gathered data from Citizens Advice's most recent customer survey of 16 suppliers - because when people are unhappy with the service they've received, they often complain to Citizens Advice about their experience.

Best Energy Company Comparison

NimbleFins has analysed data from hundreds of thousands of energy customers to see which companies are offering the best deals right now, as evidenced by growing market shares and high customer ratings.

By these metrics, the best energy company in the UK right now is Octopus Energy. Octopus has the best customer experience ratings (e.g. 4.8 stars out of 5 at Trustpilot) and their market share has grown approximately 2.1 percentage points in the past year, and even more the prior year (from an average of 14% in Q2 2023 to 22.5% in Q1 2024 to 24.6% in Q1 2025). In fact, Octopus has overtaken British Gas (2nd largest with a 23.6% market share) as the most popular UK energy company overall - although British Gas still out paces Octopus in gas supply. Third largest in terms of market share is E.ON (~15%).

Octopus's #1 largest UK energy provider ranking doesn't surprise us, as Octopus is clearly working hard at being the best. For example, they have energy deals for EVs, time of use tariffs and solar energy. This doesn't just include cheap energy deals, but also competitive payments when selling energy back to the grid compared to other options in the marketplace (July 2026 market check).

In terms of customer rating, EDF is equally as good as Octopus (4.8 out of 5 at Trustpilot).

In terms of recent market share gains, Octopus has gained the most market share (2.1 percentage points in the past year). Utility Warehouse gain 0.1 percentage points of market share in the same time period. But all other large energy suppliers lost market share in the past year.

Small suppliers in total gained 0.3 percentage points of market share.

The table below ranked energy companies from best to worst in terms of market size. We also show metrics for changes in market share to show which are losing or gaining in popularity.

The UK's 9 Best Energy Suppliers

According to data from the three months from April to June 2025, 100Green, Co-op Energy and Octopus Energy were the top three energy providers in terms of customer satisfaction. BUT we have a big caveat to point out regarding 100Green, below.

Overall, scores have dropped in the recent energy-challenged environment; but some energy providers have really tried to step up their customer service game.

For example, Octopus rose to #3 in the latest quarter with an overall score of 3.8 out of 5, from #11 a year prior with a score of 2.9. That's a huge improvement!

And Co-op Energy from #9 to #2 over the same period.

Newcomer 100Green technically topped the charts for customer satisfaction with a whopping great score of 4.8 out of 5 for Q2 2025. But, they are scoreless for the "customer commitment" category. Energy suppliers get points for the "customer commitment" for membership of the Energy Switch Guarantee and the Vulnerability Commitment. (See more about what 'customer commitment' means in the methodology section at the bottom of the article.) So without a score here, we're not sure we'd award 100Green the top spot like Citizens Advice has...

In terms of contact waiting time, the top nine companies all achieved at least 4 out of 5 stars. Broadly speaking, that's great for UK households! Less time wasted on the phone is a big win, in our book.

In terms of number of complaints category, 100Green has done the best with a 5 out of 5 score; other medium and large suppliers earned 3 or fewer stars for this category.

For reference, the average customer rating score is now 3.3 stars out of 5 (back to 2019-ear scores, and up from under 3 stars in the past few years). So overall scores had dropped after the pandemic, but they are now improving. Of the top 5 largest energy suppliers in the UK, only Octopus was ranked in the top 5 for customer service.

Note, a high ranking doesn't mean that a supplier has the cheapest rates, or that it will even be around. Previously, Affect Energy ranked in the top 5 according to the Citizens Advice data - they subsequently ceased to supply gas to all customers and had their Gas Supply Licence revoked...

Other notable change: A few years ago, Octopus reigned supreme with the top spot but they then dropped into the bottom half of suppliers. Around two years ago, Shell ranked #1, but they've since been bought by Octopus. Now Octopus is climbing the ranks again.

The UK's 8 Worst Energy Suppliers

At the other end of the spectrum, the eight worst energy suppliers in the study were Utilita (ranked the worst, again), Tru Energy, So Energy, EDF and British Gas. None of these scored higher than 2.9 out of 5 stars for overall customer satisfaction. In total, there were 16 energy companies in the study so the 'worst' is ranked number 16. However, there has been some marginal improvement in this lot, e.g. Utilita previously scored just 1.5 out of 5 stars, and they've improved to 2 now.

Ofgem, the energy regulator, has stepped in on occasion in an effort to improve customer service at the worst offenders. For instance, years ago, Iresa was banned from taking on new customers until they implemented measures such as responding to customer emails within five working days, recording all customer complaints and identifying vulnerable (e.g., those in debt) customers. Ofgem was not satisfied with the level of improvement in customer service and threatened to revoke Iresa's licence.

Note: Not all energy suppliers appear in these lists, due to lack of data. In particular, the smaller companies. Without a full data set across all categories these suppliers were excluded from the study. These suppliers might have landed on the best or worst lists, displacing another energy supplier, but we can't know without the data. Citizens Advice only displayed data for suppliers with over 25,000 customer accounts.

Methodology

We compare energy suppliers' customer service data from Citizens advice that looks at data from a number of reliable sources; suppliers with more than 25,000 customer accounts are included.

Complaints received

The complaints rating is based on data from:

• Citizens Advice Consumer Service

• Extra Help Unit

• Energy Ombudsman

• Advice Direct Scotland

Customer service wait times

The customer service rating regarding contact wait times is based on supplier-supplied data related to:

• average call centre wait time (excluding time spent in sales lines)

• proportion of emails answered within 2 working days

• average response time for social media messages (applies if the company is contacted more than 5% of the time through social media)

Customer commitment

Suppliers can score 3 points for being part of the Energy Switch Guarantee and another 3 points for the Vulnerability Commitment (with a max score of 5, not 6, if they do both). Trial members of the Energy Switch Guarantee score 2 points, not 3.

The 'Energy Switch Guarantee' means suppliers have to meet certain criteria such as completing 98% of switches within 5 working days, the whole transfer between tariffs or suppliers will be handled by the supplier of the tariff you are moving to, you have 14 days to change your mind, and more. Find out more about the Energy Switch scheme on the Energy UK website.

The 'Vulnerability Commitment' means suppliers have to promise to improve their support to vulnerable customers (i.e. those who might be facing financial difficulties or illnesses). Find out more about the Vulnerability Commitment on the Energy UK website.