Looking For the City Lights of Alien Civilizations

http://tpt.to/a27PNZK

Leaving the lights on, and you get an alien on your doorstep.

It is a bit odd for detection though, and I’m not sure if this is a great deal better than how we currently search. Or if it is at all practical. At the moment we need to use the entire spectra of a planet to tell if it’s habitable or not. Can we really see city lights now?