Excess Capacity

You had a steak, a gallon of broccoli, bread, wine, and three waters. And you still have room for the lava cake. You have...excess capacity. More capacity than you are using.

You have a two-car garage. You only own a motorcycle. The lawn mower takes up a little room in the back, but for the most part, you have a lot of excess capacity in your garage. You might rent this out to your neighbor, who wants to hide his "specialty" magazine collection from his wife.

On a larger scale, it might apply to the amount of manufacturing capacity a company has. If Flyboys Airplane Mfg, LLC., has the ability to make 100 planes a week at its facility, but only makes about 80, then it has 20% excess capacity.