Hi there, ye thats absolutely right all companys now days charge you basically rent for having there meter in your house. If you have a credit meter then it should be tied into the cost of your bill at the end of each quarter, if your pre-payment then they charge you it daily. Th only company that doesn't charge you is british gas because they put it into there rates for example.
If you were with b.g then you might pay about 8p for each kilo watt hour, where as if you are with Npower then they might charge you 15p a day then charge 3p per kilo but it depends on how much you use whether its benificial to go with b.g or Npower or whoever else.