What Size

• The garage door needs to be measured to make sure that you purchase the correct size garage door opener. Openers are sized according to door heights. For a 7-foot-tall door, a 7-foot opener will be needed.
  
  The overall door size is needed to determine what horsepower is required. Most single-car garage doors can use a 1/3-horsepower garage door opener. Doors that are 10 feet wide or more will need an opening mechanism with at least a ½-horsepower motor.
  
  

Drive System

• Garage-door openers come in three different drive systems. Belts, screw drives and chain-driven openers are available. Belt-driven openers are not very popular, and it will be difficult to find them in most hardware stores.
  
  Screw-drive motors are quieter because they incorporate a screw mechanism to open and lower the door, and they do not require maintenance as often as the other openers do. Chain-driven openers tend to be a little noisy because of the slack necessary in the chain. They are less expensive than the rest, though they do require periodic adjusting to ensure optimal performance.
  
  

Accessories

• Wall-control buttons can either be a simple doorbell-type button or a complete control panel that can lock the opener from being used. This is a good added security feature when you go away on vacation. Door-control buttons mount inside the garage near the entry to the house.
  
  Another accessory to consider is a keyed emergency release kit. These are mounted on the door and attach to the opener emergency-release handle by a cable. If the power goes out, and you need to get into the garage from the outside, a key unlocks the kit, and you can pull the release handle from the outside.
  
  

Do-It-Yourself or Hire a Contractor

• All openers come with a full set of instructions from the manufacturer. The installation process takes only a few hours and can be done by the average homeowner. If you are not comfortable with installing the opener after reviewing the instructions, a contractor can always install it for you. A call to the hardware store where you purchased the opener should put you in touch with a qualified contractor.