So when an efficiency upgrade is used it costs power, but also reduces the total power cost.

However the power cost of the upgrade itself can wipe out the eventual power saving :(

eg.
Power cost without efficiency = 28160RF
Power cost with efficiency = 53760- 15% saving = 45697
Efficiency upgrade power cost = 28160RF

Makes it pretty useless!
So the efficiency power cost needs reduced to something very small or 0.