Sorry, but you have still not made things clear.

Being honest with you, trying to get information 3rd hand like this is not ideal.
You don’t have access to their billing or account, and so you are not going to be able to give the information needed for us to work out what may be going on.
It would be better if they joined here themselves and so could then give us the answers and information needed,

When you were/are looking at the app were/are you looking at the usage figures in kWh (and/or cubic meters for gas) or were/are you just looking at the cost in £ ?

The cost in £ can sometimes show an increase even when the usage in kWh hasn’t increased.

Do they have smart meters?

But assuming that it is in fact an increased useage and not an increased cost, then the fact that it appears to have started just after they went away could be telling.

It raises questions such as:
Had they meant to turn the heating off and turned it to constant instead?
(BTW Is their heating gas or electric? Is the boiler a combi boiler? Do they also have an immersion heater?)

And again- was anyone still in the property, could anyone have accessed the property after they had left, either with or without their permission?

I’m sorry that the information I have is limited. As they are foreign students who have only been in the country 2 months, I said I would try to help. The property was completely empty while they were away and nothing was left on. Ordinarily, the usage should have been almost zero in these circumstances, however their app shows a marked increase in the number of kw used which is still the case.

I thought there might be a simple answer that somebody else had come across. I will contact OVO on Monday to try and solve this mystery.

Thank you for your responses!

Which is one reason why I was asking if someone may have got in without their permission.

All in all then I think that it would be best to have things checked out, and maybe even a meter inspection may be called for.

(I’m reluctant to mention the possible worst case scenario here, but as a Landlord I’m sure that you will be aware of the problems with cannabis farms being set up in rental properties, and while those guys usually bypass their own meter entirely they don’t care where they abstract power from and tapping into a neighbours supply while they are away may suit them well).

Thanks for the suggestions. Obviously I need to investigate further as no simple explanation seems to explain what is going on!

Re-reading this thread, I’m drawn to your comment @nodrogsbboh “however their app shows a marked increase in the number of kw used ”

It is possible that the app is showing estimated usage. You don’t say whether there is a smart meter but even with that, if readings aren’t being received they will be estimated. 
The only thing used for billing is the meter itself and so a check on the readings would be useful

Thanks. I have asked them to monitor the meter readings, especially during times when no gas is being used. It is the gas usage has shown the biggest increase. I will need to speak to someone at OVO regarding the estimated usage aspect and if/how it might affect the phone app daily info.

It wouldn’t be so baffling if someone else out there had noticed a significant change in their dual fuel usage around the 26th or 27th of last month (especially as this place was empty for about a week). If anyone has, please let me know! 

It’s more baffling that both fuels increased at the same time.

OK There could be a different reason for each fuel and it’s just coincidence, but I find that hard to believe.

For example my worst case scenario above would not explain an increase in gas usage, one reason why I was reluctant to mention it.

TBH with it being both fuels at once then it does sound more like user error in the way that your tenants are reading things.

The daily usage chart on the phone app is very simple and clearly shows, as said before, dramatic increases around the 26th/27th October. I’m starting to think that this is something OVO have implemented, for whatever reason, and I should be able to find out tomorrow!   

Our community members have given some helpful suggestions here @nodrogsbboh. I just wanted to add that this topic may be helpful: