Decreasing CPU Usage

The various "Upgrades" skills mostly reduce either Power Grid (Shield, Advanced Weapon) or CPU (Energy Grid, Electronic, etc.) usage of specific modules. Of those Weapon Upgrades is the most immediately useful skill since weapons are often such a large part of the CPU usage of a ship, in addition it allows the use of Damage increasing modules.

Increasing CPU

The Electronic skill increase the available CPU by 5% per level.

The Co-Processor I and related modules increase the CPU of the ship they are fit to at the expense on a low slot. They are very common on mining ships.

Some rigs reduce the CPU usage of specific modules but none increases the available CPU.

Finally the Hardwiring - Zainou 'Gypsy' KMB-25, KMB-50 and KMB-75 family of implants increase available CPU by 1%, 3% and 5% respectively.