In this day and age, everyone has electronics in their house or apartment. Televisions, DVD players, computers (monitors, towers, speakers, printer, etc.), cell phones, the list goes on and on. And for those of us wanting to save electricity, whether because we're eco-friendly or just want to save on our monthly electric bill, this might help.
My husband works at Fry's Electronics and one day a battery backup was on sale so he brought it home for me. The CyberPower 1500AVR with LCD screen, normally between $150 and $200 was ours for just under $100. I plugged my computer and all the accessories into it and whenever I'm not at home or go to bed, I simply shut everything down and press the power button on the battery backup. It stops the other electronics from pulling power, even though they are off.
So if you're going to run out and get one, they sell some for less than $50, but I'd suggest waiting for a good one to go on sale. For example, you have two computers plugged in and your power goes out, you might have 2 minutes to flip the switch, but if you only had one computer plugged in you might have 10 minutes. The larger, and more expensive ones, have more juice to be used. You definitely pay for quality, so do your research.