I am with sse. You fix the amount you pay per KWH. So then you pay what you use at that rate. Once a year they look at your bill, work out annual costs and see if the DD needs to go up to cover the coming year.
This is due to changes the Government made a number of years ago to stop people running up large bills they then could not pay. At the same time the company has to refund any overpayments back, which frustrates me as I am happy they keep it as it’s not a lot but means I do not feel I have to worry about putting on the heating
You can make a one off payment to them and they keep the DD at the same level
Do you have a smart meter? If so you can track daily costs and work out why it’s going up. Or is it from readings, in which cases were previous ones estimated and this is a read one?
You may well only be in one room at a time but using the washing machine, cooker if electric, fridge all costs, do you have a freezer? Dishwasher? LED lightbulbs? TV on standby, The fact that there were three of you may not be relevant, as you will still use all the appliances.
Just call them, i have never had a problem, they will explain, just don’t go off at them, it’s not necessarily their fault