What Wattage Electric Shower Do I Need: 7.5, 8.5, 9.5 or 10.5kW?

By Trinity

29th Nov 2022

6 mins read

DIY & Technical

A guide to electric shower kW ratings to help you choose the right one for your bathroom.

electric shower

Contents of this article

● Watt Electric Shower kW Can I Have?
● What Are The Different kW Ratings Of Electric Showers?
● Things To Consider When Upgrading Your Electric Shower
● Water Pressure And Electric Showers
● Which Fuse Will Be Required?
● What Diameter/Size Of Electrical Wire Is Needed?

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Watt Electric Shower kW Can I Have?

Knowing which kW electric shower you need is a difficult thing to understand if you’re not an electrician but in this electric shower wattage guide we’ll give you a clear picture of why electric showers are rated this way and which wattage will be the best for you. It’s a common question for many of us at some point or another but the answer isn’t always as straightforward as you’d probably like it to be. That's why we've produced this simplified guide to help you.

But, why is it important to know the difference between a 7.5kW electric shower and a 9.5kW option for example? Differentiating between the power ratings of electric showers is necessary when you’re buying a new system because getting it wrong will certainly leave a few members of the family displeased with you when, midway through a morning shower routine, one of them experiences a 'rainfall in the Arctic!' due to a power outage!

So, let’s take a look at some of the different options of electric shower kW ratings.

What Are The Different kW Ratings Of Electric Showers?

Unlike ordinary showers which tap into the warm water supply of a boiler or water tank, electric showers take in a cold water feed and heat it within the unit, consisting of a heating element, then emitting the heated water through the shower head.

Although kW ratings for electric showers in the UK start as low as 6kW the most common power ratings are:

7.5kW - Triton T80Z 7.5 kW

8.5kW - Mira Vie 8.5kW

The reason why electric showers come with various power ratings is all down to delivering a desired flow of heated water for the end user. If you don’t mind a low flow of water then you’ll be happy with a lower kW rating such as 7.5kW or 8.5kW; such as the Triton and Mira options above.

If you’re a shower user looking for a greater rate of water from your shower you’ll be better off buying a 9.5kW or 10.5kW electric shower like the Bristan examples below.

9.5kW - Bristan Noctis 9.5kw Electric Shower

10.5kW - Bristan Glee 10.5KW

So, why does a lower power rating electric shower give less water per minute than higher power rated showers?

This is because the water has to be heated to the desired temperature before leaving the shower head so the more water you require, the more power is required to heat it before the water reaches you.

Things To Consider When Upgrading Your Electric Shower

If the idea of a more powerful shower is appealing to you and you want to upgrade your electric shower to a higher kW rating then you’ll need to consider the following points:

● Water pressure and flow rates - Is the water pressure in your home adequate for the type of shower you require?
● Rating of circuit breaker or fuse - Can your protective device handle the amount of power?
● Size of electric cable running to the shower - Is the electric cable connecting the system to your home’s electrics suitable?

Water Pressure And Electric Showers

Water pressure is one of the biggest factors affecting decision making when buying electric showers. Before you make your purchase check with each individual system for its particular requirements.

An electric shower can be connected to your mains water supply. Your pipework will need to be at least 15mm in diameter, and you need to have a running pressure of 0.7 bar minimum in order for it to run effectively.

Which Fuse Will Be Required?

As a safety precaution your electric shower must be wired to a protective device and depending on the power rating of your system you’ll need a particular amperage. Below is a list of electric shower ratings with the correct Amps:

● 7kW - 32amp
● 7.5kW - 40amp
● 8kW - 40amp
● 8.5kW - 40amp
● 9.5kW - 45amp
● 10.5kW - 50amp

What Diameter/Size Of Electrical Wire Is Needed?

Depending on the power rating of your electric shower it will require a particular cable size which is measured in mm².

● 7.2kW - 6mm²
● 7.5kW - 10mm²
● 8.5kW - 10mm²
● 9.5Kw - 10mm²
● 10.5kW - 16mm²

As you can see, there is a lot more to buying an electric shower than pointing at one and picking it. We hope this guide has given you a clearer picture when you come to choosing the right power rating for your bathroom.

Please remember that this is just a guide to help you understand the variety of electric showers out there and why they are rated. Please consult a professional for any information or get in touch with our team for any advice.

Alan, Victorian Plumbing



Trinity is one of our expert bloggers in bathroom design and DIYs. Read her blog posts for the latest coverage of style trends and easy-to-follow guides.

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