I found this very interesting question and answer today online:
Does it cost more to turn lights on and off then it does to just leave them on?
No, this is quite false. I suspect this is a distortion of the idea that turning lights on and off stresses them and shortens their lives, but the power used is a nearly linear function of operating time.
For an incandescent lamp, there is a very brief high current impulse when they’re first turned on, but this doesn’t remotely justify leaving them turned on — it stresses filament lamps, but doesn’t require very much power.
I speak as a NASA engineer who designed the power supplies for the Space Shuttle lights. For that mission, because of limited available power, we had to research this exact issue, and concluded that the lights should only be turned on when in use.
The guy that answered the question is Paul Lutus and he was the perfect person to do so.
He also has this great quote:
“The secret to using modern social media is not locating people who actually have a particular answer, but filtering out all the people who think they have the answer”.
I also relate to him: we’ve both developed applications in Assembly language!