Each upgrade from a Mobile Base to a Y-era base (and on) requires at least one Fleet Repair Dock (or an equivalent number of Repair boxes) or a Tug and costs the EPV of the YBS. Upgrading from a YBS to a YDK requires an FRD or a Tug and costs twice the EPV difference between the YBS and the YDK.
Each upgrade from a Mobile Base to a Middle Years base (and on) requires a Tug and twice the difference in EPV.
Bases at a major planet may be upgraded without the need for a Tug or FRD. The planet is considered to have the necessary facilities for such an activity.
Unit | EP Cost | Upgrade Time |
Mobile Base Construction | MB EPV | 2 Turns |
Mobile Base to Early Base Station | YBS EPV | 1 Turn |
Early Base Station to Spacedock | 2xEPV Difference | 2 Turns |
Mobile Base to Base Station | 2xEPV Difference | 1 Turn |
Base Station to Battle Station | 2xEPV Difference | 1 Turn |
Battle Station to Starbase | 500EP | 3 Turns |
Middle Years Base to X-Base | 2xEPV Difference | 1 Turn |
While the upgrade is in progress, the section undergoing upgrade at the time of an attack will be non-functional.