Module
Modules are items used to enhance existing buildings' capabilities. They are expensive, require appropriate research, and are produced slowly, but can eventually greatly improve the efficiency of a factory.
Quick usage summary:
- For more products per second a speed module should be used.
- For more products per input resource a productivity module should be used.
- For more products per watt of energy an efficiency module should be used (except in rare cases when productivity modules are also used - then a speed module might be better).
Types of modules
There are three types of modules in Factorio, each with 3 tiers of effect. Higher tiers have stronger effects but are more expensive.
Speed Module
Speed modules increase the speed and energy consumption of a machine.
| Module | Speed bonus | Energy consumption |
|---|---|---|
 |
+20% | +50% |
 |
+30% | +60% |
 |
+50% | +70% |
Advantages & Disadvantages:
- Increases speed of machine.
- If used with productivity modules, it can increase the efficiency of the machine in terms of items produced per watt (or items produced per pollution generated).
- Increases energy use per cycle (exceptions exist).
- As a side effect it increases pollution generated by the machine, due to energy consumption being higher.
Productivity Module
Productivity modules add a purple "productivity bar" when placed inside item-producing buildings and labs. If the productivity bar is already present through completed research, the modules will simply speed up the bar. Each time the machine finishes crafting the recipe it is set to, an amount is added to the bar equal to the percentages of the productivity modules inside the machine. When the bar reaches 100%, an extra set of products is immediately generated without consuming any resources.
Productivity modules can only be used in machines that are set to make intermediate products. These are all the ores mined by electric drills, the stone brick (and anything else smelted in a furnace) and some of the items listed in the intermediate products tab. Exceptions to the items listed in this tab are: the satellite, the recipes that fill/empty a barrel, nuclear fuel, nuclear fuel reprocessing, and the kovarex enrichment process. Productivity modules cannot be placed in beacons either.
| Module | Productivity bonus |
Energy consumption |
Speed | Pollution multiplier |
|---|---|---|---|---|
 |
+4% | +40% | -15% | +5% |
 |
+6% | +60% | -15% | +7.5% |
 |
+10% | +80% | -15% | +10% |
Advantages & Disadvantages:
- Creates an additional free item occasionally.
- Increases energy use per cycle.
- Increases pollution generated.
- Slows the machine.
Efficiency Module
Efficiency modules reduce the required electricity to run the machine. The lowest amount of energy that efficiency modules can be used to achieve is 20% of the machine's base energy usage.
| Module | Energy consumption |
|---|---|
 |
-30% |
 |
-40% |
 |
-50% |
Advantages & Disadvantages:
- Reduces energy use per cycle.
- As a side effect it decreases pollution generated by the machine, due to energy consumption being lower.
- Cannot lower energy usage below 20%.
- If used with productivity modules, sometimes the efficiency gain is lower than what a speed module could achieve.
Usage tips
As a rule modules do not have diminishing returns (except that consumption is capped to -80%), that is if an assembler is making 2 items per second, adding 1 speed 3 module (+50% speed) will increase item production by 1/s, a second speed3 module will increase production by the same 1/s. Consumption modifiers work the same way, for example if a machine is consuming 180kW, the first efficiency 1 module will reduce energy use by 54kW, the second will also reduce energy use by 54kW. There is no difference between putting 2 speed 1 modules in one machine and 2 efficiency 1 modules in a second machine, than putting 1 of each in both machines - in both cases the total items produced per second and average energy required per item is identical.
There is however synergy between productivity modules and speed modules, productivity modules reduce crafting speed which lowers the production rate of items and increases the energy consumed per item, the speed bonus from speed modules increases production rate of items and lowers the energy consumed per item - in fact when dealing with productivity modules, the reduction in energy consumption from the increased speed from speed modules can be greater than the increased energy consumption. For detailed calculations on the synergy between productivity modules and speed modules refer to this discussion as well as this warning.
Filling the device with speed modules is useful when a resource is infinite but the amount of resource pools is low. The best example would be oil deposits. Another good place to use speed modules would be for assembly machines which make products that take a long time to make, for example engine units. Using speed modules allows more compact setups, because one machine can provide materials to more consumers than normal. If used together with productivity modules, they can also increase efficiency (in terms of items produced per watt or per pollution generated) of a machine.
Filling devices with productivity modules is recommended when resources are scarce. An example would be more advanced products not being produced enough due to bottlenecks. It will take longer and more energy, but the overall amount of products per time will be higher. Productivity is especially useful in recipes that consume a lot of resources per second such as electronic circuits, as this will result in a lot of free items being created and quickly cover the cost of the module. Also by saving the need to mine ore, smelt plates and process intermediates for those free items the additional energy cost can be easily covered.
Filling devices with efficiency modules is recommended for electric furnaces as these use a lot of power. Note that making higher level efficiency modules are not worth it in terms of power saved vs materials used to build a solar panel setup with same power output so the only incentive is to further reduce pollution or space utilization. Modules are also able to control pollution, as pollution depends also on energy usage. So reducing a machine's energy usage by 40% with a efficiency module 2 will also reduce its pollution by 40%. Beware as this also works vice versa! Also note that if you're using productivity modules, a speed module can sometimes provide better efficiency gains due to the fact that the machine will now be producing much more items per second. Efficiency modules also generally don't work well in beacons.
Examples of usage
Electric furnaces are huge power hogs at 180 kW per furnace. 1 basic efficiency module reduces it by 54 kW (−30%) – almost a solar panel worth of power.
Electric mining drills create 9 units of pollution with no efficiency modules and 1.8 with 3 basic ones. Same electric mining drill with 3 productivity module 3 would create 76.5 units of pollution. However if, for some reason, you were using 2 productivity modules in this drill, but are still worried about pollution, it's better to fill the last slot with a speed module than an efficiency module. This is because the extra items created per second will outweigh the additional pollution cost.