Is there any way I can make lights only come on at night?

Probably.

But... it's gonna take a lot of script-working and effort- defantly not for a novice.

You sure can, there are a few mods that do this for many lights in the cities. The script is pretty basic actually.
You just need to Disable the light during the day, and Enable it at night.

Begin If ( GameHour >= 20 )	If (GameHour <= 23 )If ( GetDisabled == 1 )       enable    Endif EndifEndifIf ( GameHour >= 0 )	If (GameHour < 6 )If ( GetDisabled == 1 )       enable    Endif EndifEndif	If (GameHour >= 6 )	If (GameHour < 20 )If ( GetDisabled == 0 )       disable    Endif EndifEndifEnd

Wow. I was about to ask about this same thing. Pluto, thank you for that script.

EDIT: Did the gamehour command come with the Bloodmoon expansion, or can it be used with the base game?

Is this actually better / faster than just doing an 'enable' without checking to see if it's disabled?

Repeatedly disabling or enabling can cause nasty side effects. It's definately worth checking.

Thanks for the info! I'll put this in my Tips file for future reference.