I was recently told that it is not good for PCs (not laptops) to be turned on and off and that I shouldn’t worry about the energy consumption as it costs the same as lighting one light bulb.
Please see below for the reply from NPower when I asked them to clarify what my source had told me.
I can let you know that it is better to turn off your pc when not in use as this uses around 1 unit (approx 11 pence) every 1.5 hours. A conventional light bulb uses 1 unit every 16 hours.
Energy Efficiency Advisor
Residential Customer Services
Tel: 0800 022 220