What Size Cable For an Electric Shower?

What Size Cable For an Electric Shower?

Selecting the right cable size for an electric shower is pivotal not only for optimal performance but more importantly, for safety.

As showers are a primary source of relaxation in our homes, ensuring they’re correctly wired ensures peace of mind.

Let’s dive into understanding the best cable sizes for various electric shower units.

What Size Cable For an Electric Shower?
Credit: @GSH Electrical

Why Cable Size Matters

Choosing the right cable size is not just a technical specification; it’s a pivotal decision with real-world implications:

Electrical Safety Risks

Using the wrong cable size is a potential hazard.

It can lead to overheating, posing a risk of fire or electrical shocks. Proper cable sizing ensures that the current flowing through the wires is safe and efficient.

Related: Fix Shower Switch Not Working

Impact on Performance and Efficiency

If a cable is too small for the required power, it won’t be able to deliver electricity efficiently. This can lead to drops in performance, making your showers less comfortable and potentially increasing energy costs.

Potential for Damage

A mismatch in cable size can strain the electric shower system, leading to premature wear and tear. This not only reduces the lifespan of the equipment but could also result in costly repairs or replacements.

Factors Influencing Cable Size

When selecting the correct cable size for your electric shower, it’s not a one-size-fits-all scenario. Here’s what to consider:

  • Power Rating of the Shower: The kW rating is essentially the “strength” of your shower. More powerful showers heat water faster and to higher temperatures, demanding higher currents, and thus thicker cables.
  • Length of the Cable Run: As electricity travels along a cable, some is lost due to resistance. The longer the run, the more significant the voltage drop. This sometimes necessitates a larger cable to maintain performance and safety.
  • Installation Method: How and where the cable is installed affects its heat dissipation. For instance, a cable buried in insulation can’t shed heat as effectively as one clipped directly to a wall. This influences its safe current carrying capacity.
  • Ambient Temperature: In a warmer environment, cables might not perform to their maximum capacity due to reduced heat dissipation. Conversely, cooler surroundings can sometimes allow for slightly increased current capacities.

Recommended Cable Sizes for Electric Showers

The kW rating of your shower often provides the first clue to the required cable size:

  • Up to 7kW: 6mm² cables are commonly used for these showers. However, always account for other influencing factors like cable run and installation type. This size might be ideal for smaller homes or apartments.
  • 7.5kW to 8.5kW: Showers in this range are more powerful and thus typically demand 10mm² cables. Remember to evaluate other installation factors and ensure you’re providing the best conduit for your shower’s needs.
  • 9kW and above: High-powered showers that offer an intense and quick-heating experience generally require robust 16mm² cables. Especially when considering longer cable runs or warmer environments, this size ensures safety and efficiency.

Electric Shower kW Cable Size Calculator

Select your electric shower’s kilowatt (kW) rating on the slide to calculate what cable size you need.


Advised Cable Size: 10mm²

Always Refer to Regulations

Local guidelines, such as the IEE Wiring Regulations in the UK, are crafted based on extensive research and expertise. These tables and guidelines are there to aid homeowners and professionals:

  • They take into account varying conditions and provide detailed scenarios.
  • Modern regulations often account for energy efficiency and conservation, ensuring you get the best out of your installation.
  • Professionals routinely rely on these standards, ensuring their installations are up to code.

Circuit Protection

Ensuring the right cable size is just a part of the puzzle. Circuit protection is equally crucial:

  • A circuit breaker or fuse that’s too sensitive or not sensitive enough can cause undue interruptions or pose a risk, respectively.
  • Modern circuit protection devices also help in energy management and can help in diagnosing potential issues in your electrical systems.
  • Always ensure that the protection device matches the demands of both the shower unit and the cable for optimal safety.


The science and art of choosing the right cable size meld electrical knowledge with practical application.

It’s always advisable to understand the nuances of your home’s electrical infrastructure.

While this guide offers a deeper insight, remember that each home is unique.

If you’re ever in doubt or feel uncertain, trust a professional electrician to make the right call for you.

Frequently Asked Questions

What is the maximum kW shower you can have on 6mm cable?

The maximum kW rating for a shower on a 6mm cable varies based on the installation method and the length of the cable run. Generally, a 6mm cable can support up to a 9.5kW shower when the cable run is relatively short and the installation conditions are ideal. Always verify with installation guidelines and a professional.

What cable do I need for a 9.5 kW shower?

For a 9.5kW shower, a 6mm^2 or 10mm^2 cable is typically recommended. The choice depends on factors like the length of the cable run, ambient temperature, and installation method. In situations with longer cable runs or less-than-ideal installation methods, the thicker 10mm^2 cable might be more suitable.

What cable do I need for a 10.5kW shower?

For a 10.5kW shower, it’s generally recommended to use a 10mm^2 cable. The length of the cable run and installation method can influence this recommendation. Always ensure that the cable can handle the current without overheating.

Can 2.5mm cable be used for shower?

A 2.5mm^2 cable is typically not recommended for most electric showers because it might not safely handle the current generated by higher kW showers. This cable size might only be appropriate for showers with very low kW ratings, but even then, it’s safer to opt for thicker cables, like 6mm^2, to ensure safety and efficiency.

Can I use 10mm cable for 7.5kW shower?

Yes, you can use a 10mm^2 cable for a 7.5kW shower. In fact, using a 10mm^2 cable for a 7.5kW shower would provide a margin of safety. While a 6mm^2 cable might suffice for such a power rating under typical conditions, opting for the thicker 10mm^2 ensures reduced resistance and a potentially longer lifespan for the cable.

Can you use 4mm cable for a electric shower?

A 4mm^2 cable can be used for some electric showers, typically those with lower power ratings such as up to 7kW or 7.5kW, depending on installation conditions. However, factors like cable length, ambient temperature, and installation method need to be considered. It’s always best to consult with a professional to ensure the cable size is appropriate for your specific needs.