My sister, who is in her 70s, has learning difficulties and several health issues.

My wife and I have started helping her manage her money as her condition deteriorated and she could no longer do it alone.

In February, my sister and I called her energy supplier, Ovo, together and she gave me permission to deal with her account. We also submitted meter readings. 

A short while later, I opened a bill from Ovo and was astonished to see that my sister had £10,824 in credit on her account. I told her and she said she'd like it refunded.

I called Ovo but was told a manager would need to sign off the refund as it was so large. But I didn't hear back, and it still hasn't been paid despite me chasing.

Now, as so much time has elapsed, Ovo won't speak to me unless I get my sister's permission again. 

However, her health problems have worsened and she is now in hospital. Her condition is such that she is not able to speak coherently. I want to register for power of attorney, but this isn't feasible at the moment.

I understand Ovo needs to make sure my sister knows what I am doing. However, she already gave permission, and it's not our fault this has taken so long.

My sister will need to pay for extra care when she is out of hospital, and the money would really help. B.D, Kent

Helen Crane, This is Money's consumer champion, replies: It is staggering your sister, who is on a low income and sometimes struggles with everyday costs, could be sitting on almost £11,000 of cash and not be aware of it.

While hers is an extreme example, she is not alone in letting it build up. 

According to Ofgem, the average amount of credit held in energy accounts in 2024 was £3.28billion, an average of £215 per household. 

This number only applies to direct debit customers, so the true figure could be much higher. 

Your sister paid her energy bills monthly, in person, by visiting the Post Office or asking her son, who also has learning difficulties, to do so for her. 

She told you she usually paid in £300 per month, but it appears she wasn't aware that her actual energy use was costing her far less than this. 

This is despite the fact your sister wasn't providing meter readings, so she would have been billed on estimates which can often be higher.   

The overpayments had been going on for many years - even prior to her account being switched to Ovo when it took over her old supplier in 2022 - which is how the  credit balance began to snowball. 

Energy firms are allowed to use money sitting idle in energy balances to bolster their own finances, so she was effectively providing a sizeable interest-free loan for Ovo. 

You asked why there was not a system in place for energy firms to flag up large credit balances with customers - perhaps when they exceed a certain level. 

Energy firms have the power to reduce the amount they take from customers who pay via direct debit, if they start to build up a lot of credit. 

Paying the bill via the Post Office means the energy firm can't intervene in this way, but I agree that a letter or phone call to your sister would have been a good idea. 

Even after you became aware of the hefty cash stash, Ovo didn't make it easy to get hold of the money that rightfully belonged to your sister.  

When you sent more pictures of your sister's meter readings - a requirement for getting the refund - you were surprised to receive an email which said her account was no longer with Ovo. 

It turned out that related to someone else's account and was sent in error.  

And after you were told the credit balance could be refunded, you waited for weeks for this to be signed off by an Ovo manager. Despite chasing it up several times, no progress seemed to have been made. 

The last time you contacted Ovo, it said it couldn't speak to you any more as your sister's permission, given in February, had expired. 

With scams and financial exploitation sadly rife, it's right that companies thoroughly check the credentials of anyone who claims to be managing someone else's money.

But your sister had already given this permission, and it was only Ovo's tardiness that required it to be given again. 

I'd also argue your circumstances were exceptional, with your sister now very unwell in hospital and urgently needing the money to help fund additional support for both her and her son on her release. 

Exasperated, you contacted me to ask if I could help. 

I contacted Ovo, and you were quickly contacted by a senior complaints manager who you said was much more helpful than those you'd spoken to before. 

He explained you had not been properly recorded as someone who could make changes to your sister's account, but this had now been rectified. 

It was also explained your sister started increasing her payments while she was with her former energy supplier, which she had been with since 2007.

The amounts kept increasing and by the end she had not been paying in £300 a month as she told you, but £405.

By the time her account was taken over by Ovo, she was about £9,500 in credit.

She did stop paying in to the account in April 2023, by which time she had amassed a credit balance of £12,700. This then slowly decreased as energy was billed for.

Ovo said that, had your sister paid by direct debit and not at the Post Office, her account would be subject to regular 'direct debit reviews' and she would have been contacted about the large balance. 

However, those who don't want to pay automatically shouldn't be discriminated against, and I fail to see why the same checks couldn't be carried out.  

Addressing the delay in responding to your request for a refund, it said photos of the meter readings weren't sent when initially requested. 

When you did send them, it found the readings were 'significantly lower' than the estimated readings used when your sister's account was switched to Ovo in 2022. 

This caused the refund request to be rejected, but you weren't told about this.  

After I contacted Ovo, these meter readings were investigated. It was discovered that your sister's previous supplier had over-billed her, resulting in a further credit to her Ovo account. 

All in all, she has now been repaid a sum of £12,000, accounting for the refunded credit and money back from her former supplier.

An Ovo spokeswoman said: 'We’re sorry for the delay and can confirm the refund has now been actioned.'

I hope this money makes a difference to your family and wish you all the best. 

I would also urge anyone who supports a family member, or anyone else, with their finances to explore a power of attorney application at an early stage. 

Sudden health emergencies are often the catalyst for seeking a POA, but having one in place beforehand can make life much easier during a worrying time.