In terms of electricity usage, does anyone know whether it is worth turning the router off when I know that I will not be using the internet for a few hours (e.g. overnight when in my bed etc.) or is it best to leave it on. Sometimes turning things on and off can cause more damage?
it will cost about £10 a year to run a router 24/7 everyday. so you are not going to see a huge saving and it's worth remembering that routers negotiate a link speed with the exchange within the first couple of weeks they are connected to find out what the maximum speed your line can handle, if you keep turning it off it will never be able to settle at the best speed.
Bottom line, they are designed to be left on all the time and work best that way.
the BT home hub II has a low energy sleep mode that is entered after a period of inactivity which cuts consumption significantly. However I always turn mine off overnight - small electricity saving and it's 100% secure switched off!