What size boiler do I need?

Why is it important to choose the right size boiler?

Put your measuring tape away. When we talk about the right boiler size, we are not referring to how tall or wide it is. We mean its power output (measured in kilowatts: kW). The higher its kilowatt output, the more heat your boiler will produce.

If you choose a boiler that is too small, you may not have enough hot water when you need it and your home may not get warm enough.

On the flip side, choose a boiler that is too large and you could end up wasting energy (and money) by using extra fuel you don’t need. That’s why it’s so important to spend time working out the right boiler size.

Factors to consider when choosing the right boiler size.

• • How much hot water you need.
    This depends on the number of people in your home, the number of baths, showers, sinks and so on, how often you use hot water, and whether you have “hot-water-hungry” appliances like a dishwasher or washing machine.
  • Number of rooms with radiators.
    Each radiator requires a certain amount of heat to warm up a room, so the more radiators you have, the larger the boiler you will need.
  • How well insulated your home is.
    A well-insulated home will lose less heat, so you will need a smaller (i.e. less powerful) boiler than a poorly insulated home.
  • The type of fuel in your home.
    If you have gas central heating, you will need a gas boiler. If your home is not on the gas mains you may have to opt for oil central heating. In which case, you will need an oil fuelled boiler (which needs more space for things like an oil storage tank).

Of course, you can always get a professional assessment from a qualified heating engineer via video call. They will be able to take into account all of the factors listed above and recommend the best boiler for your needs.

Which boiler is best for you?

Here’s a quick guide to the three main types of gas boilers to help you choose the right sized one for your home.

Combi boilers.

These are great if you live in a smaller home. They don’t need a separate hot water cylinder or cold water storage tank, so they could easily fit into a cupboard and don’t take up any of your valuable space under the stairs or in the loft (for example).

Regular boilers.

If you often use hot water around your home, then a regular – or “condensing” – boiler is probably best for you. They can take up more room than a combi as they often come with a cold water tank as a kind of back up but you’ll have a plentiful supply of water ready to be heated regardless of water pressure or any other issues.

System boilers.

Does your home have more than one bathroom? Then a system boiler is a good choice. They’re like a condensing boiler but with a large tank for storing extra hot water. Again, they take up more room than a combi boiler, but you have a constant supply throughout your home when you need it.

How to calculate the boiler size you need?

How many radiators do you have?

The number of radiators in your home is a key factor. Generally, the more radiators you have, the larger the boiler you’ll need to heat them effectively.

This is because each radiator requires a certain amount of hot water to maintain a comfortable temperature, and a larger boiler can provide the necessary flow rate to meet this demand.

Combi boilers vs regular boilers vs system boilers:

Combi boilers differ from regular and system boilers in terms of their power requirements and operation. Combi boilers are designed to provide both heating and hot water on demand, which means they need more power to heat water instantly. However, they only need to operate for a few minutes a day to meet hot water needs.

In contrast, regular and system boilers store hot water in a cylinder, which requires the boiler to heat up the entire cylinder, resulting in (you guessed it), longer operation times.

Does the size of my home affect the size of the boiler I need?

Here’s some rad advice. If you have a bigger house to heat, you’re going to need a bigger boiler. But it’s not just the size of the rooms – it’s those radiators again. As an estimate, if you have a combi boiler, you’ll need the following power outputs:

• Up to 10 radiators: 24-27kW.
• 10-15 radiators: 28-34kW.
• 15-20 radiators – 32-40kW.

If you have a system or regular boiler, then we estimate you’ll need:

• Up to 10 radiators: 12-15kW.
• 10-15 radiators: 18-24kW
• 15-20 radiators – 30-40kW.

You can see the range of boiler sizes here. A 12kW boiler will run only 10 radiators or so, While a 30kW boiler will heat up to 15 radiators or more.

This is why it’s so important to work out the right size boiler. Remember, these figures are only a rough guide. You may want to talk to a heating engineer to get a more expert opinion.

How many bathrooms do you have?

The number of bathrooms and the number of people taking showers or baths will affect the size of the boiler you need.

A regular or system boiler is recommended for homes with multiple bathrooms, as a combi boiler may not provide enough hot water.

For multiple bathrooms, a boiler size around 35-42kW is needed, while for one bathroom, a 10-25kW boiler should do the trick.

Does boiler efficiency matter?

It certainly does. Boiler efficiency is all about how much energy your boiler uses to heat water – and how much is wasted. Obviously you will want a boiler with the highest efficiency rating (A). This is an efficiency rating of about 90%. The lowest boiler rating (G) means that it has only a 70% rating – or less.

To put these ratings into some kind of context, that means that for every pound you spend heating up water in your G rated boiler with a 70% rating, 30p (or more) of it is wasted.

Fortunately, only very old boilers are G rated and in fact regulations now require that all new boilers installed have an Energy-Related Products rating of 92%.

Still, don’t assume your boiler is super efficient. Check it and see what rating it is. You may want to check its rating and consider getting a more efficient one to replace it.

Calculating your hot water demands.

We can help you calculate your specific hot water requirements with a video survey. By taking into account factors like how many people use hot water in your home, when the hot water is used and how much, we can work out the best boiler for you.

About Dabonn

Zhengzhou Dabonn Energy Co., Ltd.

We have more than 20 years of experience in boiler system equipment research and development and manufacturing. And committed to designing and producing boilers that suit your needs, including fire-tube, water-tube, and steam boilers, while also staying up-to-date with the latest technological boiler.