I've not seen the ad but, the only reference I know states "A heavily used (500,000 starts/yr) non-regenerative elevator in a high-rise commercial building would use about 15,000kWh/yr (Enermodal 2004)"
Not sure if my maths is right but I think that equates to about 1.7kW
If so for overnight a complete waste of energy going back. Leave the lamp running. If Anthony is right about the month then it would be worthwhile.
After typing all that...I think I need to get a life...this is the Intermission forum after all!
I knew this was a mistake; my grip on reality's not too good at the best of times. Glitz, in "The Ultimate Foe"