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What size electric boiler do I need?

When it comes to installing an electric boiler, understanding the correct size is crucial to ensure it meets your heating and hot water needs efficiently. The size of an electric boiler is measured in kilowatts (kW), which is a measurement of power rather than the physical dimensions of the unit. To guarantee that you install an electric boiler that can meet your home's requirements, follow the instructions in this guide.

For electric boilers in Birmingham, Solihull, Tamwoth, Sutton Coldfield, and surrounding areas, contact us today at 0121 405 0404.

what size electric boiler do I need?

So, what size do I need?

The power output of boilers is measured in kilowatts (kW), which helps determine how much heating and hot water the boiler can handle. In simple terms, the higher the kW rating, the more radiators and taps it can supply simultaneously. 

Electric boilers typically have output ratings up to 15kW, which makes them suitable for smaller to medium-sized homes with lower heating and hot water demands.

Gas and oil boilers, on the other hand, can have substantially higher output ratings, making them more suitable for larger properties with greater heating and hot water needs. Therefore, it's important to consider your specific requirements when choosing an electric boiler.

Here at AllForProperty, we recommend adding 1.5kW per radiator to your home. So, if there are eight radiators, a 12kW electric boiler will suffice for central heating.

Besides heating, you also need to consider your hot water demand. Electric boilers are generally suitable for smaller households with moderate hot water needs. If you have a high demand for hot water, such as multiple bathrooms or frequent simultaneous use of hot water, you may need a higher kW rating or a supplementary system to meet this demand.

What happens if the electric boiler I chose is the wrong size? 

Undersized Boiler

If you install a boiler with a low output rating, it will struggle to meet your home's heating and hot water needs. An undersized boiler will be under constant strain, leading to inefficiency, increased wear and tear, and potentially higher maintenance costs. It may also fail to maintain a comfortable temperature during peak demand, especially in colder months.

Oversized Boiler

Conversely, if you install an electric boiler that is too powerful, your energy bills will quickly skyrocket. An oversized boiler will cycle on and off more frequently, leading to inefficient operation and wasted energy. Additionally, the initial cost of a larger boiler is higher, which can be an unnecessary expense if the extra capacity is not needed.

This principle applies to all types of boilers, not just electric ones. Therefore, selecting a boiler with the best output rating for your home is essential to ensure efficiency and cost-effectiveness.

Consulting a Heating Engineer

If you're uncertain about the boiler size you need for your home, the best course of action is to hire a heating engineer to conduct an inspection. A professional can assess your specific heating and hot water needs, considering factors such as the size of your home, the number of radiators, insulation levels, and hot water usage patterns. This assessment ensures that you choose a boiler with the appropriate output rating.

Additional Considerations:

Energy Efficiency

When choosing an electric boiler, examine its energy efficiency rating. Modern electric boilers are designed to be extremely efficient, converting almost all of the electricity they consume into heat. Choosing an efficient model will help you save money on your energy bills while also helping the environment.

Installation & Maintenance

Proper installation and frequent maintenance are critical to the long-term performance of your electric boiler. Ensure that the installation is completed by skilled personnel, and plan monthly maintenance checks to keep the system functioning efficiently. Regular maintenance can help identify and treat possible concerns before they become severe problems.


When choosing a boiler, consider your long-term needs. Consider this while making a decision to extend your home or use more hot water. Choosing a somewhat larger boiler or one with adjustable settings allows for future adjustments without requiring a complete replacement.

Get in Touch With Us Today!

Our engineers at AllForProperty are available throughout Birmingham, Solihull, Sutton Coldfield, and Tamworth. We can help you select the right boiler for your home, ensuring optimal performance and efficiency. To schedule a consultation or for further assistance, call us on 0121 405 0404 or use our contact form.