Efficiency is analogous to corruption in Civilization games. The further away a base is from your Headquarters, the higher the proportion of energy is lost due to inefficiency. Minerals and nutrients are not affected. If you have a large number of bases, you will also receive more drones at bases due to "bureaucracy". The less efficient the base, the more drones will appear. Efficiency is modified by the map size. On larger maps, the rate at which efficiency drops due to distance from your Headquarters decreases, and the number of bases required to increase bureaucracy drones increases.