You have to pay to have access to energy even if you don't use it through what's known as the daily standing charge. If you've both gas and electricity, the average direct debit standing charge is £300/year before you use owt. This is something Martin has challenged Ofgem on.
It's worth noting there are variances in standing charges by region (for example, if paying by direct debit in London it's £246/year, in North Wales and Mersey it's £332/year) – Ofgem says it is due to the different costs to transport power to where you live.
From October, the high daily standing charge will increase very slightly, rising to £303 a year on average.