Millions of customers could be due a refund from their gas and electricity company but if you don't know about it and don't ask, you might not get it.
If you pay your energy bills by fixed direct debit, it's easy to go month by month without thinking too much about it. You know the same payment will be taken automatically each time. The downside is that you could be paying more than you need to without realising it.
Fast-forward several months and you could be owed several hundred pounds, based on our survey of 3,950 Which? members in July 2019 who pay their energy bills by direct debit.
Two thirds are in credit with their energy firm, and a handful have built up a balance of more than £1,000.
You're allowed to request a refund of excess credit at any time, and your supplier should review your account periodically, but some companies make it easier to get your money back than others.
Read on to find out if you're due a refund, if your energy company will pay it automatically or how to request your money back.
Just one in 10 customers in credit have been reimbursed without having to ask, according to our research. Only 8% have asked for credit to be refunded, but 92% of those who asked got their refund.
If you are in credit to your energy firm, you can request a refund at any time and your energy supplier must do so promptly, unless there are reasonable grounds not to. It will likely check whether your payments and credit will cover your predicted use over the next year, and require an up-to-date meter reading.
This is to make sure that a refund won't result in you paying more or getting into debt in future.
Whether it's worth requesting a refund will depend on:
Some energy firms pay interest on customers' credit balances so it's worth factoring this in before you request a refund:
Of the 13 biggest energy companies (excluding prepayment-focused suppliers), only seven will automatically refund your credit.
Usually they will do this at the annual review of your direct debit. But the threshold for the refund varies. Use the table below to find out your supplier's policy.
If your energy firm doesn't pay automatic refunds, you'll need to keep an eye on your account. Your energy supplier should review your account periodically to check that your direct debit remains accurate, however we've heard from members for whom this didn't appear to happen.
Anne Sanders, from Hertfordshire said: 'Four or five years ago I joined First Utility and was put on very low monthly payments. I built up a debt, so my monthly direct debit was increased to pay it off. But it was never lowered again.
'When doing a Which? survey, I went online and found out how much credit I was in with my provider (now called Shell Energy): £728.36!
'Previously, I didn't keep an eye on my direct debits: they just go out of my bank account. It was the fact I wasn't told how much credit I had that annoyed me.
'But getting a refund was easy. I used the live chat function on the website and they suggested I took a refund of £550 and kept the rest as credit for winter. I received the money within a week.'
When you sign up to pay by direct debit, your energy company will work out your monthly payments by taking the total expected cost of the gas and electricity you will use over a year and dividing it by 12.
So your payments will be the same every month, even though your usage changes. This helps stop shock bills in winter.
In winter you will use more energy than you pay for, as you turn on the heating, use more lighting, and perhaps use your tumble dryer more. As a result your account could go into debt. But this is nothing to worry about if your direct debit is set accurately because in summer you will use less energy than your payments cover and pay off the debt.
Over a year, your total payments and total energy use should match up.
We've seen a few companies request higher direct debits in the winter than summer. Watch out for this if you want a consistent payment all-year round.
Most of the 13 energy firms' websites we checked made it relatively straightforward to ask for a refund. Often, you can do this through your online account or by filling in a form on its website.
You can also ask your energy firm to reduce your direct debit payments to use up your credit gradually. Bulb has recently begun automatically reducing direct debit payments for customers who have built up excess credit. Other firms (British Gas, Eon, Npower, Octopus Energy, Ovo, Scottish Power and SSE) let customers adjust their own direct debit via their online account or app.
You can't change your direct debit to any amount you wish though. Eon, for example, limits changes to 20% of your current payments. Npower suggests an alternative payment account that you can accept or reject.