What kW Boiler Do I Need For A Terraced House?

According to the Office of National Statistics, terraced houses accounted for approximately 26.5% of all dwellings in England and Wales in 2021.

Terraced houses are typically compact, with the average total floor space ranging from 688 to 1,087 square feet (64 to 100 square meters). With one in four living in a terraced house, what kilowatt (kW) boiler are these households using?

Before discussing the kW size of boilers, let’s first look at what the average UK terraced house looks like.

What Does The Average UK-Terraced House Look Like?

For those unsure of the exact definition of a terraced house, it is a property where the side boundary walls are shared with neighbours. These terraced homes are usually developed in long rows alongside each other and are popular in cities where space is at a premium.

According to the Office of National Statistics, terraced houses are one of England and Wales’s most common dwelling types, totalling around 5.7 million homes.

Energy efficiency-wise, terraced houses are generally better than semi-detached and detached homes. However, the Office of National Statistics stated that age (when it was built) is the most significant contributing factor to a dwelling’s energy efficiency.

Energy Performance Certificates (EPCs) indicate how energy-efficient a dwelling is. EPC scores dwellings’ energy efficiency between 1 and 100 based on the data about a building’s energy features, such as:

• Building materials used
• What heating system it is using
• And what type of insulation the dwelling is using

Depending on your final efficiency score, you are issued a banded section between A and G. For a home to achieve an A, it has to score above 92, while for it to be awarded a G rating, it has to score below 20.

The average EPC rating for existing terraced dwellings in England was 66 (64 for Wales), with newer homes scoring 84 (same for Wales).

Terraced homes are typically more affordable and often bought by first-time buyers and young families. The average terraced home will have 2 to 3 bedrooms, 1 to 2 bathrooms, a kitchen, and living space. If we follow the generally recommended amount of one small radiator in compact areas and two to three for larger rooms, we can assume:

• A radiator per bedroom
• One per bathroom
• Walkways and entrances will have one
• Two for the living area
• And one in the kitchen

This means that your average terraced home could have six to nine radiators.

Please bear in mind that this is a rough estimate. To correctly gauge a room’s radiator heating requirement, you need to work out the size of the room (height included), the insulation, how many British Thermal Units (BTUs) your radiator needs to produce to warm the space efficiently, and more.

Choosing the correct radiator for each space can save you money.

Now, if we compile all the data we’ve shared in this article, the average UK terraced home will have the following:

• A family of three members
• Roughly eight radiators
• Will have an average EPC score of 74 (selecting the midpoint between older and newer terraced homes)
• Two bedrooms
• One bathroom
• A living area
• Short entrance area
• And a kitchen

Also, our average UK terraced home has a floor area of 887.7 square feet (82 square meters).

Now, we can discuss choosing a boiler with the correct kW rating for an average terraced house.

How To Choose A Boiler By kW For Your Terraced Home

There are three types of gas boilers you can select from for your terraced house, but we’d strongly recommend choosing a compact, efficient, and smart device-compatible combination (combi) boiler.

A boiler’s power output is measured in kW. kW indicates the amount of heat energy it can generate. The higher the kW rating, the more powerful the boiler is.

Combi boilers perform two roles: providing hot water and heating. The rating, which is usually shown to potential clients (the kW on the advert), refers to its power output for producing hot water. The second rating, which refers to its heating capability, is usually lower.

Factors that will determine the kW size of the boiler you need for your terraced house are as follows:

Property Size

The size of your property will directly affect the power of your boiler’s kW rating. Larger properties will need more kW power, while smaller ones will need less.

Be aware that selecting a boiler with too little power means radiators will not reach the desired temperature, and your kitchen and bathrooms will not have enough hot water during peak demand.

Before buying the largest combi boiler on the market, larger units are inherently more expensive to purchase and install, which can be a financial mistake. While modern condensing boilers can adjust to lower working loads, it’s only advisable to go this route if you plan on extending the property.

Other reasons why property size determines the size of your boiler are also down to other factors like:

• Heat demand for larger spaces
• More radiators
• Heat loss due to property size
• And more bathrooms

Number Of Bathrooms And Hot Water Demand

As you’d expect, the number of bathrooms in your terraced property will also affect the kW power output needed from your boiler.

The more bathrooms your home has, the larger the boiler’s kW rating needs to be.

Another overlooked factor is how and when your family uses the hot water, which will significantly affect the size of the boiler and its flow rate, or litres per minute (LPM).

Knowing a combi boiler’s LPM indicates whether it can meet hot water demand. Modern combi boiler flow rates can vary from 9 to above 20+ LPM.

Also, be aware that if your water mains pressure is low, this will affect your combi boiler’s flow rate, which can be improved with booster pumps.

Number Of Radiators

A property with many radiators will need a boiler with a higher kW rating. Radiators’ primary purpose is to ensure that heat is distributed evenly around the home.

If you select a boiler that is too small, certain sections of your property will be cold.

Radiators are one of the main factors that dictate how powerful your boiler needs to be.

However, by combining the abovementioned factors, you can determine what kW rating your boiler needs for your terraced house.

Calculating Your Boiler’s kW Requirement

As mentioned, the average terraced house in the UK has around eight radiators. Radiators’ heat output is generally measured in BTUs or kW.

Most radiators require 1 to 1.5 kW of heat, but again, this can vary depending on where they are installed in your home. If we assume that our eight radiators need 1.2kW each, it is a simple multiplication equation, or:

Eight radiators X 1.2kW = 9.6kW radiator demand from your combi boiler

Now that you’ve worked out how much heat energy your home’s heating system needs, it’s time to figure out your hot water demand.

Each bathroom generally requires around 3-5kW of heat energy. Kitchens are typically excluded from the basic kW calculation due to their lower hot water demand from combi boilers.

Also, most kitchen tap LPM requirements are lower than those for bathrooms, with most only requiring a flow rate of around 5 to 6 LPM, with a shower or a bath needing between 10 to 15 LPM.

For a basic kW requirement calculation for a terraced home, your radiator needs 9.6kW, and the single bathroom will require an additional 3kW.

Your average terraced home will need a combi boiler with 12.6kW.

Before calling the calculation done, you will want to work in a safety kW margin of around 15% to ensure that the combi boiler can handle an extra load.

To calculate the safety margin is simple:

12.6 X 1.15 = 14.49kW combi boiler.

Now that we’ve gone through all the steps to selecting the best boiler based on its kW rating for your terraced house, who can you call to have it installed within 48 hours?

WarmZilla Can Help You

If you’re feeling overwhelmed by the information in our blog, you can take our easy survey. Answer the questions to the best of your ability, and WarmZilla will suggest a great boiler for your exact needs.

If you still have questions, please feel free to contact one of our many experts.