Grain Silos are used for offline income. Each silo adds an hour of income before any upgrades.
There are 2 different permits. One of them requires an in-app purchase.
The free, default permit. Allows for the construction of two silos.
It costs $4.99 or £4.09. Allows for the construction of ten silos. Permit is kept when you sell your farm or restart.
The base cost of each silo is listed in the following table. The first silo appears by default.
Formula for cost: (Number - 1) ^ 10 * 10,000
There are three Epic Upgrades that can increase the money production factor of silos.
Silo Capacity allows you to increase the away-time by six minutes per level. There are ten levels, maxing out at an additional one hour per silo.
Silo Quality increases the percentage of income you make while away (the game is not running on the foreground of your device), by two percent (2%) per level. There are 40 levels, maxing out at an additional eighty percent (80%) income while you are away. As of V1.4, silos now change appearance depending on quality and capacity.
Cheaper Contractors reduces silo and hen house construction costs by 5%. There are ten levels, reducing the cost of silos by 50% when fully researched.