Harvesters

Water / Iron Harvesters
These generate iron and water in your base. The higher your Central Computer level, the more of them you can build in your base. Upgrading them makes them store more resources and gather faster. They need full power to work at 100%; if you don't have enough power they gather resources more slowly.

Stats:

^ Water Harvesters need only iron to build, Iron Harvesters need only water.