The size of the garbage disposal you need will depend on a few factors. First, you'll need to think about the type of sink you have. If you have a double sink, you'll need larger disposal. You'll also need to think about how much food waste you generate. If you have a large family or entertain often, you'll need larger disposal. Finally, you'll need to think about the type of power you need. If you have a septic tank, you'll need a 1/2 horsepower disposal. If you have city water, you can choose between a 1/2 or 3/4 horsepower disposal.