Although there are a few charges associated with electricity usage, you can still get an idea of how much usage you can get for 10 pence. Whether it be 100 watt bulb, a kettle, television, or any other electrical appliance in your home.
Just enter your pence per KWH, on a 2 tier tariff use the second rate.
If you pay 14.6954 pence per KWH, enter it as 0.146954
Most appliances have the KWH rating stamped either underneath, or behind them. For an appliance rated at 2 KWH, enter this as 2000 watts.
1000 Watts = 1 KWH