Depending on where you live, it's almost inevitable that you'll lose power in your neighborhood at least once. A lot more, if you live in Los Angeles. And what if there's an emergency and you need to leave in that time and your car is stuck in your garage?
When the power fails,you garage door is fairly easy to open manually, it just takes a little know-how. Every garage door opener system comes with an override manual option. You just need to know where it is. Usually it is a cord that hands down from the track between the opener and the garage door. If you pull down on this change, you'll hear a pretty loud pop sound, which means that the garage door is free from the electrical opener and will be able to swing open. Then you can just grab it by hand and force it open, and then you can pull your car out.
Be sure to reconnect the door when the power comes back, or else your stuff will be able to be stolen pretty easily. To reconnect, simply click the garage door opener, and the track will begin to run. When this noise stops, pull the door manually into the open position very slowly, and this will allow it to reengage with the pulley system. It will make a discernable lick to let you know when you have been successful.