Why won't my garage door close when the power is out?

Your garage door won't close when power is out because garage door opener requires electricity to operate motor that moves door, and without power, opener cannot drive door closed, though manual operation is possible. Garage door openers are electric motors that run on 120 volt power, and when power is out due to outage, tripped breaker, or unplugged opener, motor has no power to move trolley that pulls door. Safety sensors also need power to function, and without power, opener logic board will not allow operation. To close door manually during power outage, you need to disengage opener from door by pulling emergency release cord, which is red cord hanging from trolley, down and toward door to disconnect, then manually push or pull door closed, as door should move freely when disconnected if springs are good; if door is very heavy, spring may be broken. Once closed, engage manual slide lock on door track to secure door, as opener no longer locks door when power is out. Some openers have battery backup that allows one or two open and close cycles during outage, indicated by beeping, so if you have battery backup and it still won't close, battery may be dead and needs replacement costing 30 to 50 dollars. To prevent being locked out during outage, install emergency release kit with outside keyed lock. After power returns, re-engage trolley by pulling cord toward opener and running opener until trolley reconnects.