A garage door opener is sized by the door and by the people who use it. The same motor can be right for a small household with a single compact car and wrong for a family with tall vehicles and heavy storage. Start with the fit, then the features, then the comparisons you can make yourself.
Measure the headroom and the track
Measure from the floor to the highest point the door reaches when open, and from the top of the door to the ceiling. Check whether the opener's rail or track fits the ceiling space with room for the header. If you have a lift, a high roof, or ceiling storage racks, add those obstacles to the list before you choose a rail style.
Match the opener to the vehicles you park
Roof racks, cargo carriers, and tall trucks can strike a door that is opening normally. Park each vehicle where it normally sits and measure the clearance to the door track and the opener rail. Note which vehicles get used most, since a garage that sees daily traffic places very different demands on the motor than one that opens only now and then.
Look at door weight and balance
A heavy door asks more of the motor. Ask whether the door is insulated, whether it has glass or a heavy frame, and whether the springs are balanced. A balanced door is easier on any opener. Read the door's weight rating if the manual lists one, and compare it with the opener's listed capacity.
Think about who uses the remote
Count everyone who will open the door, including teenagers, guests, and anyone who helps with errands. Decide whether you want a keypad, a wall control, a phone app, or a remote for each vehicle. Keep a list of who holds which remote in your home file so you can update it when someone moves out.
Check the safety sensors
Confirm the photo eyes are mounted at the height the manual calls for and that they are aligned. Test the auto-reverse with an object on the floor, not by stopping the door with your hand. Then check the garage door opener page for typical service life and when to plan a replacement.