[RFI] Turn off the whole house to locate noise sources?

[garyk9gs]

I have a question regarding the "turn off the whole house" recommendation. 
Before doing so, do you search all of the ham bands looking for noise, say in conjunction with the P3 set to wide span? Or do you look at the whole spectrum from the AM bcb to 30 mHz?
I have a pretty quiet location but I still want to eliminate the noise offenders in my own  house.
And then repeat after the main breaker is turned off?
I suppose it makes sense to do the low bands during the daytime and the higher bands at night when thrre are fewer real signals?
One other question regarding switch mode power supplies like cell phone chargers and laptop power supplies.   If the are plugged into the wall but not connected to, say a phone, is that good enough or should they actually be supplying current to a device?

73-Gary K9GS