Received an email from British Gas to let me know that I was £178 in credit. On the same email I was informed that they are increasing my monthly DD by approx £15 per month! Where's the logic?
The energy cap is rising by about £700 in April. They have probably taken that into account, calculated in your credit balance and arrived at £15pm to cover the extra.
As pointed out above. Clearly the rises are going to be more than the amount you have overpaid, so that will be used up and you will still have to pay another £15 a month.
Seems not too bad to me, you should see my fuel bills.
It's known as arithmetic. They work out what you use, subtract, the current balance, extrapolate likely prices add a bit on for insulation and divide by 12. At some point in the year your balance should tend toward zero, you cannot read any meaning into an isolated balance, especially coming out of the winter.