In the last 20 years moving across many many suppliers I have never had a supplier that wasn't good at "guessing" and have never had an estimated bill that was more than a few pounds adrift from the actual usage.
Well OVO seem to be very poor at guessing. They have my smart meter readings from May last year (theoretically) - though they only seem to have them since they rebranded SSE to OVO a couple of months ago not from when they took over SSE, nor do they have records from when SSE was owned by SSE ( I do, monthly, in a spreadsheet). SSE were pretty good, and if they got it wrong they were willing to change it over the phone.
Or are you referring to their monthly DD amounts? Again I have never had a supplier that set a DD amount at a level that didn't equate to a good approximation of annual cost - for example when my last gas supplier went bust the credit they owed me was £3. Of course at times the credit was higher than that because consumption of gas over the year isn't linear, but provided the balance approached zero once a year then it isn't an issue for me.
OVO are repeatedly trying to up my DD, I'm assuming they want the cashflow because they are having difficulty with the cap compared to the real cost of fuel. Though the last time I looked wholesale electricity price were well covered by the CAP price , but not gas. I'm not consuming gas - just electricity and there is only a small difference for my usage in winter over summer. I heat with a woodburner which does water and radiators, and in summer I use electricity for water heating, plus I often have to use a de-humidifier or the house gets damp. This evens out my usage, this may be unusual but is obvious from my records.
And that will be the issue for the suppliers.
Those who will be demanding *their* money back from the supplier if the suppliers increase the direct debits in anticipation of the further significant increase in price this autumn will be made up of those who do have sufficient cash to pay whatever bill arrives and those who do not.
When the £400 discount hits the electricity accounts then the companies are going to have lots of fun with people phoning up and asking for that to be paid back to them.
Then there is the government decision to pay the £650 to those on means tested benefits to them through additional payments to benefits rather than to the energy suppliers. Now some will use that money to pay for the increased fuel bills, but I predict an awful lot will not.
Over the winter the debt the gas and electricity companies are going to build up will be staggering, as there won't be the credit from the higher DDs of the summer to balance out, the £400 will have been repaid, the £650 will have been frittered away, and if the energy companies exercise the option of cutting people off (where they can, as they are limited in who they can and cannot) then they will be crucified in the press.
This is going to be interesting. At present prices the 400quid rebate will be about 3/4 of my annual bill, the increased direct debit will be racking up further credit amounts and I will be definitely wanting it paid back to me. I plan to try and reduce the direct debit online once they have taken one payment at the increased amount, if I can, and will be trying to reclaim any credit above £100 on a regular basis ( which seems daft to have to do and is the opposite of what the direct debits were supposed to achieve).
It will be "interesting" to see what happens with the Cap in October. My reading of the cap values compared with wholesale electricity and wholesale gas prices (particularly the cost of gas for 1 year delivery) is that electricity customers are subsidising gas customers. I wonder if that will continue or even increase as such a large % of British homes are heated with mains gas. If it does it won't be good for the switch away from fossil fuels.