The Tekkit Classic Wiki

Cables are the primary means of transferring EU (Energy Units) from one device to another. There are several different tiers of cables, depending on how much Voltage they can tolerate. If too much Voltage is applied to a cable, it will instantly melt but it can take unlimited amounts of "current" (EU/t) in the right Voltage-Range (EU-Packet). Different tiers are made out of different metals. Furthermore, all cables suffer from distance-related energy losses - long cables will inevitably lose energy in the process of transferring it. There are several ways to offset it - Transformers and insulation. For higher-tier cables, the insulation also reduces the amount of shock damage the player and NPC's receive from touching the cable under high voltage.

Insulated cables can also be painted using the Painter. This separates them, preventing cables of different colors from interacting with each other. This also greatly reduces the strain on CPU, as large cable meshes with many intersections require the game to perform many CPU-heavy calculations.

Power will not flow unless something is using power - sources of power do not "push" power out, it is "pulled" from them on demand. In more detail, blocks that consume power (machines, BatBoxes, etc) will attempt to draw power from surrounding blocks to fill their internal storage. If connected to a wire, they will "search" along the wire looking for a connected power source. When a power source is found, the consuming block will try and pull power out of the power source. If the power source cannot provide any, the search will continue until either power is drawn, or all possible sources (if any) have failed.


Power is transmitted in packets of EUs, called EU-Packets or EUPs, that each contain a certain amount of EUs. The amount of EUs that a packet contains determines its voltage.

Different generators and storage units provide different voltages. It is important to use the correct cable to carry higher voltages, as your cable will be destroyed if the voltage is too high for it (see the table below).

Basic machinery can handle Low Voltage, but will explode if powered with higher voltages. Advanced machinery (from the Advanced Machines mod) can handle Medium Voltage, but no higher. Transformers can be used to "step down" higher voltages to lower ones).

The following table explains the various voltage levels and their sources.

EU/Packet Voltage Minimum Cable Sources
1 to 5 EUs Micro Voltage Ultra-Low-Current Cable
or better
Solar Panel, Water Mill, Wind Mill
32 EUs Low Voltage (LV) Copper Cable
or better
BatBox, Generator, Geothermal Generator,
Low Voltage Solar Array, LV Transformer, Nuclear Reactor*
128 EUs Medium Voltage (MV) Gold Cable
or better
MFE Unit, MV Transformer, Reversed LV Transformer,
Medium Voltage Solar Array, Nuclear Reactor*
512 EUs High Voltage (HV) Glass Fibre
or HV Cable
MFSU, HV Transformer, Reversed MV Transformer,
High Voltage Solar Array, Nuclear Reactor*
2048 EUs Extreme Voltage (EV) HV Cable Reversed HV Transformer, Nuclear Reactor*

*Different voltage levels can be produced by a Nuclear Reactor, depending on how it is set up.

Different voltages can travel down the same cable at the same time. When power is mixed like this, its voltage is considered to be the highest of the voltages being carried (i.e. LV + MV = MV). (remember that this isn't the best way to tranfers big distances)

Current and Wattage

Current is the number of EU-Packets that flow through a device or cable within a given period of time, regardless of voltage; whereas wattage can be considered as the number of EUs that flow per second, regardless of the size or number of EU-Packets that carry them.

Power sources have a maximum current that they can provide, usually one packet per tick (20 a second). For example, a BatBox can provide one Low Voltage EU-Packet, containing 32 EU, every tick.

Cables can carry any amount of current, as long as the voltage is low enough for that cable. For example, an unlimited amount of 32EU packets can pass through a copper cable each tick, but a single 128EU packet will destroy the cable.

Power Loss

The longer a cable is, the more power it will lose over distance. How much power is lost depends on the type of cable and how well insulated it is. Energy losses are rounded to the nearest EU, meaning a length of cable will lose no power at all if it is short enough.

  • Tin Cable can only carry Micro Voltage, but it can carry that power with no loss for almost 40 blocks before power is lost. This makes it extremely useful for connecting Solar Panels, Water Mills or Wind Mills to a BatBox a long distance away.
  • Insulated Copper Cable will lose 1EU/Packet after the first 4 blocks. Since Solar Panels emit EU-Packets containing only 1EU each, connecting a Solar Panel to a BatBox with more than 4 blocks of Copper Cable will lose ALL of your power! Try using Tin Cable instead.
  • Glass Fibre Cable has extremely low loss, losing only 1EU/Packet every 40 blocks.

Energy loss of a cable is applied to every EU-Packet, NOT the total EU/tick passing through it. Therefore, as an example, a gold cable carrying 128 EU/tick at Low Voltage (4 EUP/tick) will lose 4 times as much power as it would carrying 128 EU/tick at Medium Voltage (1 EUP/tick). This means higher voltages are more efficient to carry power over long distance.

Tin Cable Copper Cable Gold Cable HV Cable Glass Fibre Cable Detector / Splitter Cable
EU/b1 EU loss EU/b1 EU loss EU/b1 EU loss EU/b1 EU loss EU/b1 EU loss EU/b1 EU loss
Uninsulated 0.025 1 EU every 40 blocks 0.3 1 EU every 3.33 blocks 0.5 1 EU every 2 blocks 1.0 1 EU every block 0.025 1 EU every 40 blocks 0.5 1 EU every 2 blocks
Insulated (1") --- 0.2 1 EU every 5 blocks 0.45 1 EU every 2.22 blocks 0.95 1 EU every 1.05 blocks --- ---
Insulated (2") --- --- 0.4 1 EU every 2.5 blocks 0.9 1 EU every 1.11 blocks --- ---
Insulated (3") --- --- --- 0.8 1 EU every 1.25 blocks --- ---

1 EU loss per block of cable passed

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