When the power goes out your garage door openers battery backup system will continue to operate your garage door through about 20 open and close cycles.
Operating your door manually is no fun, especially in areas with frequent power outages.
It has been reported that every month 100,000 homes experience a power outage in the USA. A battery powered standby system allows you access to your home when the power is out.
In 2005 it was reported that 50 million Americans were without power in the largest blackout in U.S. history. I recall that here in the Midwest many cities did not have full power restored for several days.
You have probably experienced short term power outages in the past. While living in a rural area, I once went without power for 3 1/2 days. This was a localized outage, not widespread as the one in 2005.
When the power goes out, the system provides the power for the opener, safety reverse and safety beam components, keyless entry pad, wall control, motion detecting console and other accessories.
All the major manufacturers market a battery operated garage door opener. This system helps ensure you have access to home and garage during a blackout.
Sears has offered the Craftsman belt drive operator with a 12 volt Diehard deep cycle battery backup system.
Sears is revamping their offerings and have little information online at this time.
Chamberlain's Liftmaster division offers the 475LM EverCharge™ battery backup system with a few of their DC powered operators.
Genie does not currently offer one of these systems. Their website is going through changes at the present time - not certain what their offerings will include.
If you are looking for a replacement for your current system, you may want to consider replacing with a battery operated garage door opener.