Turn off all the lights in a district (including at all the houses) until the bunker power is turned on. Headlights, fires, and lamps could still remain - but houses? All off.
Allow these lights to be subsequently turned off or controlled at the bunker. I’d prefer a darker world, so my lights would be mostly turned off except for in the bunker.
The problem for me is not that all light is on, when you enter a house. The problem is, that you are not able to turn all light off. Yes, some wall switches actually work, and some lamps respond to bullets and turn off. But how do you kill the ceiling lights? When lurking around inside a house to get a good shot at a machine outside, the ceiling lights are rather annoying. So please keep the light on, but fix the wiring to the wall switches 
The fact the lights are all on seems legit to me, people obviously left in a very great hurry, not even clearing away food plates or locking their doors, but as IanForce says, having working switches to control everything makes sense and would be a good addition.
Having civilian lighting controlled via the nearest militray bunker makes no sense, the grid would be different.
However as a gameplay thing it works well. Are those lights in the distance a farmhouse or a machine? You have to get closer to find out, seeing lights is always a good means to attract the player towards an event or place as well. This game seems to start on the very day the incident happened or very soon after so lights on has a logic to it. After a month you’d get grid failures and power station shutdowns and the lights would go out. Given that all the post-apoc games I’ve played have a dead smashed world, I find Generation Zero’s almost still alive and normal world refreshing.
There is a lot of very very dark world away from the buildings as well!