A greenhouse can be sized as little or large as you need it to be, from a few cold frames to an entire additional building. Greenhouses on average can produce roughly 2.5 pounds of fresh produce per square foot every year. Using that statistic would be beneficial when planning for how much produce you will need for your household.
Greenhouses can grow a couple pounds of produce per square foot per year. Estimating exactly how much your greenhouse will grow for your household would be related to how big the structure is. A greenhouse that is a few feet wide and a few feet long will still produce a good amount of food, but a bigger one would ensure more yield, especially if something like inclimate weather or unforseen crop soilage occured.
