If they are fluorescent (CFL) then each time you turn it off and back on it shortens the life of the bulb.
Neither kind uses more electricity when you turn it on. It is a myth than any bulb uses a big surge of power as you turn it on. It doesn't.
Recent energy saving bulbs are better than the older ones,who took 10 mins to reach full brightness.
Look at consumer tests and also the boxes. Some bulbs 'heat up' very quickly and others might take longer.
I've found some brands are better than others.You want bulbs that state 'fast warm up' or 'instant on'.
Personally, I'd turn off any light bulbs and not leave them on. After all, you would wouldn't boil up a kettle if you didn't need the hot water.Both are a waste of energy.
Even most energy efficient bulb use electricity. For example if 100 people let their 20 watt energy efficient bulbs on that's mean they are consuming 2000 watts from nearest power station. So it is better to switch off the bulb when not in use. Yes there is a chance of short life span of bulb if it's frequently switch on and off. In that case buy an LED bulb. And if you leave the room for just 30 to 50 seconds then it's not a big deal.
I've heard that every time you turn a light on or off it uses 10 min of electricity. So if you are leaving the room for less than twenty minutes you would save more energy by leaving the light on.
Yeah I've heard that it's not worth switching it off if you're leaving the room for less than 15 mins. If it's longer then switch it off.
Someone told me ages ago that it is cheaper to leave them on rather than turning them on/off every time you leave/enter a room. I know you should turn off the old style bulbs, non energy efficient, but I'm only talking about the energy saving ones. Thank You
