Power generators come in three forms, the Solar Panel, Hydroelectric Power Generator and the Thorium Reactor. Each Solar Panel can create up to 1kW and both the Hydroelectric Power Generator and the Thorium Reactor can create up to 5kW.
Solar Panels need to be in either bright light from the surface at day, or Lightonium / lightning from the Storm Gun. If an area is bright enough then Solar Panels can be vertically stacked with Wooden Platforms and still generate power.
The Hydroelectric Power Generator requires a sufficient water pressure difference to create power. Water pressure is dependent solely on the distance from the top of the body of water regardless of vertical obstruction, not its total volume, and can be determined by hovering over a full block of water with a Water Detector attached.
The Thorium Reactor generates 5kW continuously without any inputs.