Switching suppliers

Saldawop

My mum is with EDF, on the Standard tariff for both Gas and Electricity.
Her estimated bill for the year is approx £750!!

She currently pays in the bank when she gets her bill.

According to Uswitch, if she changes to npower and pays by direct Debit she would save over £150.

There are two types though.Fixed or Variable Direct Debit.
May sound silly, but what is the difference?
Variable= they send you a bill and your account will debited the full amount?
Fixed= You pay a fixed amount per month, if you use less electric you are in credit?
But ,assuming thats right, what if you use more?Do they bill you for the extra?

John

Npower will try to average your usage over the year and spread the payments accordingly . With the tariff I am on there are 6 monthly reviews . Just had mine and they are refunding £200. If I owed them, they would bump the dd up by the shortfall /12