What size boiler do I need? Boiler size guide


What size boiler do I need? Boiler size guide

At Plumr we understand that choosing and sizing your boiler can become complicated. 

The first thing to consider when working out the size of the boiler you need, is how much work you require it to do. How much heat and hot water you need will determine what kind and size of boiler you should go for. Choosing these factors correctly will ensure that your home/space is heated efficiently and hot water is at your disposal, without creating high energy costs. The type of boiler system you need will also affect its size.

Gas boiler option for your home

Gas boilers use natural or propane gasses to heat the water in the boiler to boiling point. The steam that is created is then transferred through pipes to feed to the individual radiators in the rooms of your home. Choosing a gas boiler that is too small for your home, will not heat and provide hot water efficiently. Choosing one that is too big will leave you with unnecessarily expensive energy bills. By calculating the square feet in your home you can determine the correct boiler size. 

What size gas boiler does my house need?

When you brought your home, you were likely informed of the house’s size. If you do not have this information to hand you will need to benign by measuring each of your rooms. The correct way to measure a room is start in the corner of your room, measure the two walls that meet in this spot and then record the dimensions. You’ll need to complete this step for each room in your home and record the measurements. Once all have been recorded, you’ll need to convert your measurements into square feet. 

Then you’ll need to calculate the BTU’s (British thermal units) needed to heat your home efficiently. To be effective, your boiler should produce 50 Btu per square feet of your home. Multiply the square footage of your home by 50 to get a rough size estimate. There are other factors that can affect the size of the boiler you need, therefore this method only gives a rough sizing idea. How well your home is insulated and other variables that affect heat loss, can have an impact on your boiler size requirement.

Combi Boiler option for you home

A combination boiler is one of the most common boiler types installed throughout UK homes. A combi boiler fills both hot water and heating demands. They are practical and efficient systems which are low cost to run. The size of your combi boiler will heavily depend on the amount of bathrooms in your home, family size and your demand for hot water. Your combi boiler system will heat water as you need it so the correct sizing is crucial with this type of system. 

What size combi boiler does my house need?

Before considering the factors affecting which boiler size you need, it is important to understand how boiler size is measured. Consider the output of the boiler in kilowatts (kW) rather than the physical dimensions of the boiler. A kilowatt is a unit used to measure how much energy the boiler provides in heat. The higher the heat and hot water demand, the greater output your boiler will require. These three factors will assist you in sizing your boiler:

  • The number of radiators.

  • The number of bathrooms (with non-electric showers).

  • The number of people in the home (the demand for hot water).

Why choosing the right size boiler for you house is important

As boilers come in a range of outputs choosing the right one for your home is crucial, here are a few reason why it is super important: 

  • If it’s the wrong size or output the boiler won’t be able to meet your homes heating requirements.
  • If your boiler isn’t the right size, it can cause you to use too much energy, leading to higher gas bills that will affect you.


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