Blackouts happen even in the nicest of neighborhoods. It's pretty much a foregone conclusion that your home will lose power at least once in the next few years. What if there is some sort of an emergency and you really have to leave, but you can't open your garage door to get your car because the power is out?
You should know that, even if power fails, you can open your garage door by hand. It only requires a little bit of knowledge and elbow grease.
Every garage door opener system comes with a manual open option, the key is to know where it is. Normally, it is a string or some sort of cord that dangles down from the metal tracks that run between the opener motor and the door itself. If you yank on that hard, you will likely hear a large popping or cracking sound, which is a signal that you have released the door from the electric opener and it is now free to be manipulated manually. Just take the door and force it open with your hands- it should move fairly easily. You are then free to pull out.
However, don't forget to reconnect your poor door to the electric mechanism when the power is back on, because when its not attached anyone can open it and steal the stuff in your garage. To re attach it, hit your garage door opener button, and wait for the track to begin to run. When that sound is over, pull the door open again, slowly, re-engaging with the system of pulleys that keep it in place. It will click when it is properly re attached.