Minecraft Joule

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Minecraft Joules (or MJ for short) is a type of energy introduced by BuildCraft. It is generated by machines called Engines and can be used by any kind of BuildCraft machinery. Many types of energy can be converted to MJ by using Engines, however, transforming MJ into other power types is a more complex process, and requires the usage of energy conversion machines found in other mods. MJ can travel through Kinesis Pipes or, before BuildCraft 4, in Conductive Pipes.


MJs are made by all types of Engines. Redstone Engines generate MJ just with a redstone signal, but others like the Combustion Engine need Fuel or other resources to produce MJ. Redstone Engines are used mainly to power Wooden Transport Pipes and Wooden Waterproof Pipe, due to their low outputs, a higher-tier engine is advisable in order to power machinery.

List of Engines and Generators[edit]

Name Max Output (MJ/t) Source Mod
BioFuel Generator 16 MineFactory Reloaded
Biogas Engine 5 Forestry
Blulectric Engine 23+ RedPower 2
Clockwork Engine 1.5 Forestry
Combustion Engine 6 Buildcraft 3
Commercial Steam Engine 4 Railcraft
Electrical Engine 14 Forestry
Hobbyist's Steam Engine 2 Railcraft
Industrial Steam Engine 8 Railcraft
Magmatic Engine 4 Thermal Expansion
Peat-fired Engine 2 Forestry
Redstone Engine 0.05 Buildcraft 3
Stirling Engine 1 Buildcraft 3
Stirling Generator 1 EnderIO
Steam Engine 2 Thermal Expansion
Steam Turbine 16 MineFactory Reloaded


Main article: Conductive Pipe
Some Golden Conductive Pipes carrying MJ. The cyan beam in the pipes is MJ.

Engines can place their MJ into a machine, or a Wooden Conductive Pipe (which can be then attached to other Conductive Pipes).

Conductive Pipes are like wire for MJ to travel trough. Stone Conductive Pipes have a 5% energy loss by each block, and Golden Conductive Pipes have a 0.5% energy loss by block. When MJ is traveling trough a Conductive Pipe, a cyan beam is seen inside the pipes. MJ traveling a Conductive Pipe is seen in the right of this page, note the cyan beam inside the pipe.

Redstone Energy Conduits do not have a distance related energy loss. Instead, there is a loss for how many inputs points the energy travels through. Anytime energy enters a Redstone Energy Conduit network, 5% of the energy is lost.

Thus any power line longer than 10 blocks is more energy efficient if Redstone Energy Conduit is used, while purely from an energy efficiency frame shorter cables are better as Golden Conductive Pipe.


Other power types can be converted into MJ. EU, IndustrialCraft2's power, can be converted into MJ by using an Electrical Engine. Blutricity, RedPower 2 power, can be converted into MJ by using a Blulectric Engine, which takes blutricity and outputs MJ. MJ can be converted into EU by powering a Magma Crucible with Netherrack or Cobblestone inside it that generates lava, and then put that lava into a Geothermal Generator or a Thermal Generator; the Magma Crucible will take MJ and the generator will output EU, with an efficiency that depends on what resource is melted in the crucible and which generator is used to extract EU. The most efficient version of this process allows the resulting EU to be converted back into MJ with a properly upgraded Electrical Engine with no loss.

RF Conversion[edit]

Redstone Flux (RF) is automatically converted into MJ by any Energy Conduit at a rate of 10:1.

Using Power Converters, it is possible to convert each MJ into 10 RF.

Using Transfer Node (Energy) from Extra Utilities, it is possible to convert each MJ into 10 RF.

Using the Universal Cable from Mekanism, it is also possible to achieve a 10:1 conversion ratio.

EU Conversion[edit]

Lava Source Generator MJ per Lava EU per Lava EU per MJ
Cobblestone Geothermal Generator 24,000 20,000 0.83
Cobblestone Thermal Generator 24,000 30,000 1.25
Netherrack Geothermal Generator 12,000 20,000 1.67
Netherrack Thermal Generator 12,000 30,000 2.5

Using Power Converters it's possible to convert each MJ into 2.43 EU.

Using the Universal Cable from Mekanism, 4RF (0.4MJ) will yield 1EU, meaning a ratio of 1MJ : 2.5EU is achievable.