This is an uber long shot because it was not a story I read, it was described to me in a paraphrased and shortened way, but its intrigued me ever since.
The premise of the story involves humanity inventing the ability to "create" space, and jumping on this to solve Earths lack of space issues. You could install a door in your home and instantly have a new room, which didn't physically take up space on your land.
This became a standard feature of homes, with most rooms being "fake space", and people giving the rest over to large gardens. Or apartment buildings suddenly being able to house tens of thousands of people - just need corridors and space for the door.
The story ends something along the lines of:
... and then the power went out.
The implication of this was that:
the fake space required power to be sustained, and when the power went out the fake space disappeared, along with anything inside it, such as people...
I was told this story somewhere around 2005, so its no newer than that.
From the simplicity of the ending, I am guessing its an older sci-fi work, but I could be wrong.