In the event of a long-term, grid-down scenario, many of us are prepared with alternative light sources: lanterns, (fuel & battery operated), candles, glow sticks, flashlights, etc.
Have you given any thought to those who are unprepared and their reaction to your lit house? Imagine the desperation when their decorative candles and flashlight, with one set of batteries, runs out.
Consider being prepared to black out your windows. This simple act will hide your alternative light sources from those becoming desperate in the dark. It can be as simple as hanging heavy blankets over your windows. Another choice is installing blackout curtains. Any way you choose, know that if the grid is down long-term, any light emanating from your home could draw in the "zombies"!
I purchased a neat "black out" shade @ Walmart. It was inexpensive - accordian style with sticky tape on the top. Just cut to fit the window ( I would cut to the outside dimensions in order to be sure to cover the entire area around the window), it comes with clips to hold it up when you want to view outside. I have had mine over a year and it has remained intact w/o any problems. It looks nice too.