Automated Factories and buildings such as Mechanical Saws or Small Furnaces need the power to work.
The power is generated by power plants such as Wind Mill, Water Wheel, or Coal Power Plant.
Each factory has power sockets for transferring the power. Sockets become visible when you select anything from the building menu.
There are three ways to connect factories with power plants using the sockets:
1. By horizontal and vertical Torque Rods that need to be plugged into at least one socket of a building. And as close as possible to belts.
In this picture, you can see a power plant on the left side with a power socket that remains visible after plugging a torque rod.
And a plugged belt on the right side without a socket.
2. By belts because they distribute power too even though the sockets are not fully visible.
3. You can build a power plant right next to a factory or building so their sockets plug into each other even though they are not fully visible.
In the right panel, you can check the power lines and see the amount of power going in and out.
When there is less power going in, the whole system gets slower.