How much you need to grow will depend on how many mouths you have to feed, and what you're growing. Greenhouses have the capability and potential to feed just one person or a whole community. It is all dependant on how large the greenhouse is. Warehouse sized greenhouses can feed entire communities.
A greenhouse can feed as many people as it needs to. The size that it is built at is the determining factor. For example, a 20x40 square foot greenhouse can eliminate the need for grocery stores for the average family of four.
