Hi @wkeithg , I’m not sure that’s the right way around. Your overall usage should come from your meter which is calibrated - although the half hour usage isn’t quite as accurate. 
Your charging usage, depending on set up, comes from either the charger app or charge anytime app which is one step removed. Agreed that you would expect it to be correct but I can’t see how it would be more accurate than directly from your smart meter. 

It’s not my overall usage I’m querying but the estimated breakdown they give (which is truly smoke and mirrors and I don’t really know why they do it). In the app and on the web page OVO gives you a breakdown of energy usage.  It’s obviously an estimate as they don’t know what energy is used for, just the total and the 30 minute chunks.  I guess they just assume peaks at mealtimes are cooking and others are washing and dishwashers and overnight ones are car charging.  However as I’m getting a rebate on Charge Anytime they know exactly what I’m using to charge car and it is considerably more in kWh and considerably less in £ than they show in the estimate.  
it really is a pure guesswork.

Hi @wkeithg 

In the app you can view a breakdown of the usage and I know they use technology to work out a guess of what appliance is using what based on smart meter usage, but it can’t be 100% sure what’s being used as it can’t see - it can only judge based on an average amount of power being used at the time.

There’s a little more about that on this topic below:

 it can’t be 100% sure what’s being used as it can’t see 

The point I’m making is that it ovo CAN SEE my charging!

That’s a good question @wkeithg, I’ll put this one to the team.