Almost 13 million households across the UK are owed money by their energy supplier, with an average reclaim amount of £136.

However, one in 10 billpayers could be entitled to more than £200 in overpaid credit.

Compared to last year, the amount of outstanding credit has risen 13.5% or £230m to a total of £1.7bn.

The research from comparison and switching service uSwitch.com found that around half of billpayers don’t know how to claim a refund while one in 10 don’t know whether they are in credit or debt to their supplier.

How might you overpay your energy provider?

If you pay for your energy by direct debit, you can find yourself in credit as the monthly payments don’t exactly match your gas and electricity use.

While the direct debit amounts stay the same every month, energy use naturally changes during the colder and hotter months of the year. This means you should be in credit with your supplier following the summer months, and in debt to the provider during winter.

But uSwitch reveals that 46% of UK households will come out of winter this year being owed money.

Some energy providers don’t automatically issue refunds to customers whose accounts are in credit, meaning any money owed can go unclaimed for months. Almost six in ten (57%) report that their energy supplier has never automatically credited their account.

And for half, they’re not aware of how to claim outstanding credit.

However, uSwitch also found that nearly four million households (14%) are in debt to their provider at the end of winter, a total of £548m for the UK. This is an average of £142 each.

How to reclaim your energy credit

During the coronavirus lockdown where finances are under pressure, uSwitch said billpayers should think about whether they want to reclaim the credit, or use it as a buffer to help pay for the extra gas and electricity they will use while at home.

The majority of suppliers either refund automatically or allow you to fill in an online form which is the best route as call centres are experiencing high call volumes from more vulnerable customers during the coronavirus pandemic.

Below is a list of 10 suppliers, the average amount owed to customers and how to reclaim your money:

EDF Energy: 45% of customers say they are in credit by an average £181.33. Current customers can provide meter readings which can be supplied to EDF, either online, through the app or over the phone, in order to access a refund. If you have already left EDF, you can request a refund via the help and support  section of the EDF website.

Scottish Power: 42% of customers say they are in credit by an average £150. If a customer’s annual review is based on actual meter readings and the balance is greater than one month’s payment or over £75, the balance will be automatically refunded. If customers wish to request a refund outside of their annual review, they will need to provide a meter reading.

Ovo Energy: 53% of customers say they are in credit by an average £143.94. You can ask for a refund if your balance is at least £25 more than one month’s Direct Debit payment. A recent meter reading will need to be provided.

Shell Energy (formerly First Utility): 39% of customers say they are in credit by an average £141.96. Customers in credit can request a refund, although Shell Energy highlights that credit levels may vary throughout the year. If monthly payment amounts are too high, Shell will recommend reducing the regular payment.

SSE: 38% of customers say they are in credit by an average £139.08. Every six months, SSE reviews customer usage against what they are paying, with a Direct Debit review taking place annually. If the review finds you’re paying too much and are in credit, they will automatically refund you. Outside of this review period, a meter reading will need to be provided and a customer will need to fill out a refund form.

British Gas: 46% of customers say they are in credit by an average £134.60. British Gas will put up to £75 of your credit towards your future bills but you can request a refund online, through live chat or your account.

Octopus Energy: 51% of customers say they are in credit by an average £134.13. Customers can request a refund emailing hello@octopus.energy.

Npower: 52% of customers say they are in credit by an average £130.60. Annual reviews take place for Npower customers. If you’ve built up a credit of £25+ on either your gas or electricity, it will refund it automatically – as long as the statement was based on an actual meter reading. Customers can call at any time to discuss a credit refund but a meter reading will need to be provided.

E.on: 48% of customers say they are in credit by an average £129.55. Customers can request a refund but a meter reading will need to be provided and future Direct Debit payments may need to change.

Bulb Energy: 51% of customers say they are in credit by an average £112.86. If a customer’s account is in credit by more than their monthly payment amount, email help@bulb.co.uk to ask for a refund. A meter reading will need to be provided and these can be submitted before you get in touch.

Sarah Broomfield, energy expert at uSwitch, said: “At a time when many people are finding their finances squeezed as well as using extra gas and electricity because they have to stay at home, this will be welcome news for anyone sitting on unclaimed credit from their energy supplier.

“More than a fifth of households say that the amount of credit or debt they’re in has increased in the last year, and we hope that providers will act quickly to make sure that direct debit payments accurately reflect energy use.”