Why are my monthly payments so high when I am always in credit?

I am paying nearly double of my actual useage and recently had a considerable refund for an overpayment. Why is my monthly payment still so high?

I don’t know your personal circumstances, but if you are paying double you actual usage then go to your “Payments and statement” on your dashboard and then select “Payments setting” from there you can reduce your monthly direct debit to a more appropriate figure.

You can use this facility to prevent a large build-up of credit but need to bear in mind Bulb require one month advance payment plus your possible increased energy usage during the forthcoming winter.

To add what Allanr has said, Your monthly payments are based on your yearly usage (kWh) divided by 12, during summer usage is generally much lower so you are paying more than you use, so building credit, during winter when usage is higher you will in theory be paying less than what is used and the excess credit will balance this out.
This ensures a stable monthly payment plan.