I do sympathise about PowerUp, I went through the pain of signing up, and the ongoing niggles when the App would not allow a purchase, but on the whole I am pleased with it and it has saved me money. The commercial idea is good and I am told the Apps are working, but the system has been set up separately to SP's normal metering and billing system and it is the interface which causes the problem. I agree that it should not be promoted in its current state and it does SP no credit at all. A dedicated help line team would be great because the normal help line team do not seem to be briefed on PowerUp problems.
When they get the interface sorted out SP need to address other details. My PowerUp bills say it would be cheaper to buy a contract because I am on PowerUp variable, but I have always bought 6 month contracts. The bills also suggest I should switch to a fix Aug 17 to save money, this in Apr 18 when the Aug 17 deal has long expired. It also tells me on my gas bill the cost of running a dishwasher and laptop, come on, these are not gas appliances. These do not affect me financially but it gives a poor image for the process. Finally the price increase announced this month gives options for payment by Direct Debit or Quarterly Cash - neither apply to PowerUp which uses prepayment by credit and debit card.
I concur with Davc, the signup isn't great, and the app is a bit rough around the edges, but the commercial proposition suits me really well and it's definately saved me money on my electricity.
If you can, I'd advise stick with it. I've not had to replenish yet but my initial 6 month payment went through great and it's been fine keeping an eye on things.