An apparatus associated with a public electricity distribution network to determine charges for the supplied electricity where the period during which consumption is measured (the metered period) is longer than the period used for settling the price or value of the electricity (the settlements period) and where the charge can be determined for either the metered period or the settlements period. The apparatus further provides means for adjusting charges such that the total charges equals the total owed or that total minus a defined amount. Means are also provided whereby the apparatus does not require metered data from all consumers connected to the network. The apparatus also provides means for determining the value of the supplied electricity where a plurality of generation sites exist each of which separately valued.