The power grid is the backbone of any factory. It provided electrical power across your factory. Any Generators attached to a grid work together to power the factory. If your power demand is greater than your production machinery attached to the grid will run slower.
Generators
Wind Power
Wind power is your Tier 1 power source you gain access to right at the start. Cheap to build, but very weak. Turbines also must have a large clearance around them, preventing any form of high-density power generation. The power produced by the turbines is also dependent on the planet - Wind speed varies planet to planet.
Thermal Power
Thermal power is a Tier 2 power source you gain access to early on. This allows you to burn fuel to produce power, allowing higher density power generation, but requires a constant flow of fuel. If you run out of fuel, your factory will grind to a halt, including any mining machines you have gathering coal. Cascade failures have been known to happen if you rely only on thermal generators and do not watch your fuel reserves.
The duration a piece if fuel will last is based on its MJ value. Thermal generators suffer a 20% loss due to inefficiency. to calculate how long a Fuel unit will last, multiply the MJ rating by 80% (or 0.8), then divide it by the 2.16MW that the generator produces per second. The resulting number will be how long one unit of that fuel will last.
Example 1: Coal has a energy density of 2.7MJ. take away the efficiency loss (2.7 * 0.8) and you are left with 2.16MJ. Divide that by the thermal generators max production (2.16MJ / 2.16MW) and you get that one piece of coal will burn for one second at full use.
Example 2: Hydrogen Fuel Rods has a energy density of 40MJ. take away the efficiency loss (40MJ * 0.8) and you are left with 32MJ. Divide that by the thermal generators max production (32MJ / 2.16MW) and you get that one Fuel Rod will burn for 14.8 seconds at full use.
Solar Panels
Solar Panels is another Tier 2 power source you gain access to early on. Much like wind power each panel is weak, however they do not have a spacing requirement, and you can cram as many as you would like onto a planet surface. Their big drawback is they only function during the day, requiring accumulators to store excess power for use during the night. The power produced by the panels is also dependent on the planet - Solar intensity varies planet to planet.
Transmission Towers
Tesla Towers
The Tesla Tower is the main power pole you use early game. It allows you to connect generators to your buildings, and spread the range of the power grid. It has a decent supply area, but suffers when trying to run long distance.
Wireless Power Tower
The Wireless Power Tower is your long range power pole you use early game. It allows for large gaps to be spanned, spreading the range of the power grid much further than its smaller companion. It has a pitiful supply area, but excels when trying to run long distance. It can also recharge the Core in the Icarus Mech if you stand next to the pole.