In-game description:
"Greatly reduces all production and construction times.

The Nanite Factory produces highly advanced nano-robots which dramatically reduce the construction and upgrade times of all buildings, the production times of spacecrafts and defensive structures. Higher levels will produce more sophisticated and efficient nano-robots reducing construction times greatly.

Each level cuts the construction time for buildings, ships and defenses."

Nanite Factory along with Robotics Factory is unique in the sense that it can reduce it's own build time, incidentally making it impossible to see base build times past first level.

Build Time* Effect
0 -- -- -- -- none
1 2,000,000 1,000,000 200,000 150:00:00 -50.00% Build/Production Time
2 4,000,000 2,000,000 400,000 13:38:10
3 8,000,000 4,000,000 800,000 13:38:10
Reqs. Nanite Factory requires Robotics Factory Lv.10.
Legend *modified by Robotics Factory and Nanite Factory.