How the scores are worked out

We compare energy suppliers' customer service by looking at data from a number of reliable sources. We rank suppliers with more than 25,000 customer accounts.

Complaints received

We base our ratings on complaints made to:

• the Citizens Advice Consumer Service

• the Extra Help Unit

• the Energy Ombudsman

• Advice Direct Scotland

Contact waiting time

We use data from suppliers to work out:

• their average call centre wait time for customer service

• the number of emails they answered within 2 working days

• their average wait time, or number of contacts answered within 2 working days for online messaging

Online messaging can include: webchat, WhatsApp, SMS, in-app messages through the supplier’s own app, and customer account portal messages.

Billing and metering

We use data from suppliers to work out the number of customers who received an accurate bill:

• in the last 6 months if they have a smart meter

• in the last 12 months if they have a traditional or non-smart meter

We measure billing accuracy by looking at how many bills are based on a meter reading, rather than an estimate.

We also look at the number of smart meters operating correctly at the end of each quarter. This follows the methodology set by Ofgem and the Department for Energy Security and Net Zero.

Customer commitments

We base our ratings on suppliers’ membership of the Energy Switch Guarantee and the Vulnerability Commitment.

If a supplier is a member of the Energy Switch Guarantee, they have to meet certain criteria - such as completing 98% of switches within 5 working days. Find out more about the Energy Switch scheme on the Energy UK website.

If a supplier is a member of the Vulnerability Commitment, they have to promise to improve their support to vulnerable customers, who might be facing financial difficulties or illnesses. Find out more about the Vulnerability Commitment on the Energy UK website.

Suppliers score 3 points for membership of the Energy Switch Guarantee or the Vulnerability Commitment. If they're a member of both, they get 5 points. Trial members of the Energy Switch Guarantee score 2 points.

If we don't have data for your supplier

Suppliers are legally required to share the data we use in this rating. If they don’t, we score them zero in categories related to these things.

If a supplier doesn’t have a referral system to our consumer service, they won’t get a complaints score. This means they won’t appear on our main table comparing suppliers.

How we come up with a star rating

We give energy suppliers a score out of 5 for each category. 5 is excellent and 1 is poor. Then we give them an overall star rating out of 5.

If a supplier scores at the cut-off of 2 ranges they will score the higher of the two ratings. For example, if a supplier has responded to 80% of emails within 2 working days, they will receive a 3 rather than a 2.

How the categories affect the overall score

Not all categories are equal. Some, like complaints, count more towards the final score than others.

This is how we work out the overall scores.

How we separate suppliers that get equal ratings

If two suppliers receive the same overall score, the supplier with the lower complaints score will receive the higher overall ranking. 

If the two suppliers have the same complaints score, we use a tie breaker formula to decide on their ranking. This tie breaker formula uses the same method as the main star rating score, but uses the original data that we receive from suppliers (excluding the complaints score and customer guarantees score.) This has the effect of awarding the supplier with the better customer service performance the higher ranking, even if the difference in performance is small.