As a rough estimate **most flats, apartments and smaller houses, with up to 10, average size radiators and 1 bathroom* will require a 24 to 27kw Combi Boiler**. For a medium to large 3-4 bedroom house with up to 15 average size radiators, 1 bathroom and an ensuite* bathroom, a 28-34kw Combi Boiler would be installed.

## How do I work out what size boiler I need for my house?

A good way of determining the size of boiler you need is to **count your radiators around the home**. Obviously the more you have, the more power the boiler will need to deliver to make sure they are all piping hot.**Count your radiators**

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

## How many radiators can a 30kW combi boiler run?

15 radiators

How Many Radiators Can a 30kW Boiler Run? For combi boilers, sizes from 28 to 32kW can keep **between 10 and 15 radiators** nice and toasty. On the other hand, 30kW heat only and system boilers can heat 15 to 20 radiators, making them the ideal choice for running larger properties.

## Is a 30kW combi boiler enough?

As a rough guide most apartments and smaller houses, with up to 10 radiators will require a 24-25kw boiler. **A 28-30kw would be installed for a medium to large 3-4 bed house with up to 15 radiators**, and a 33-35kw and a 40kw would be for a large house with anything up to 20 radiators.

## What size combi boiler do I need for a 4 bedroom house?

Combi Boilers

As your home has four bedrooms, you would require a combi boiler with an output **between 35-43kW**. If you live in a medium sized home with up to 15 radiators, you would most likely need a 35kW boiler, whereas if you live in a large house with up to 20 radiators, you’ll need a 43kW boiler.

## What capacity combi boiler do I need?

As a rough estimate most flats, apartments and smaller houses, with up to 10, average size radiators and 1 bathroom* will require a **24 to 27kw** Combi Boiler. For a medium to large 3-4 bedroom house with up to 15 average size radiators, 1 bathroom and an ensuite* bathroom, a 28-34kw Combi Boiler would be installed.

## How do I choose a combi boiler?

You should consider how much hot water you and your family use, the size of your property, the fuel that is available to you, your existing system and the types of boiler you can have installed. You may also want to consider other factors such as energy efficiency and options for renewable energy use.

## What happens if a boiler is oversized?

Oversized boilers ‘cycle’ on and off excessively, i.e. **they heat up too quickly, run for short blasts and then turn off because they are too hot**. Each fire up is something close to full capacity which dumps a huge amount of heat into the system and overheats the radiators.

## What happens if my boiler is too small?

If your new boiler is too small, **it might not be powerful enough to properly heat your home, or give you enough hot water**. On the other hand, getting a bigger boiler than you need could lead to wasted energy which’ll take its toll on your bills and on the environment.

## How many bathrooms can a combi boiler run?

two bathrooms

Some combi boiler manufacturers have found the right balance of providing lots of hot water without compromising efficiency, but the maximum they can do is still only **two bathrooms**.

## Can you have a powerful shower with a combi boiler?

Combi boilers are incompatible with boiler pumps, which means that **power showers cannot be installed with a combi boiler system**. Electric showers can, however, help improve the water pressure in a shower slightly. System boilers and regular boilers can be connected to power showers.

## How many kW does it take to heat a 4 bedroom house?

The best system boilers for a 4 bed house will have an output rating of **between 18 kW and 26 kW**. Homes with more radiators (up to 15) will need an output rating closer to 26 kW.

## Can you fill a bath with a combi boiler?

Nearly all combination boilers can cope with heating systems in larger houses. **You can fill a bath almost twice as quick with a 42kw Worcester than a 24i Junior model**. A 100 litre bath would take about 5 and a half minutes to fill with the larger boiler, but just over ten minutes for the smaller model.

## How many kW Do I need to heat my house?

The first and the easiest method to calculate your home’s heating capacity is laid down in the ‘building code’ basics: **one kilowatt of heat will be required for heating every 10 square metres of your home**. Hence, for heating a 100 square meters home, one will need to look for a 10 kWh boiler type.

## Can you run 2 showers off a combi boiler?

**Some large Combi boilers can produce 16L per minute hot water which is enough for 2 showers**, however if you’re not getting 16L per minute cold water into the boiler off the main it will only heat up what you give it.

## Does a higher kW boiler cost more to run?

Does a higher kW boiler cost more to run? **No, it doesn’t**. Bear with us here. It’s true that a 36kW boiler will cost more to run than a 24kW model – after all, you pay for each kW you use.

## Are double radiators better than singles?

For standard sized and large rooms, **double panel radiators are by far the most efficient**. Single panel radiators emit less heat because they have less surface area for the heat to come from.

## How do I calculate boiler kW?

For example, if the boiler runs for 1,800 seconds, dividing 12,558,000 by 1,800 gives 6,977, or a little under 7,000. This is the heat input rate, measured in joules per second, or Watts. **Divide the heat input rate by 1,000 to convert it to kilowatts**. 7,000 divided by 1,000 gives a rate of 7 kW.

## How many radiators can 24kW boiler run?

A 24kW combi boiler can run ten household radiators. On the other hand, a 24kW system boiler can run **up to 15 radiators**. As a rule of thumb, experts calculated that one radiator requires about 1.5kWs.

## How many radiators can a Worcester 30CDi run?

15 radiators

The Worcester Bosch Greenstar 30CDi is suitable for reasonably large properties, up to 4-5 bedrooms. Just keep in mind that you’ll need a large heating run and **up to 15 radiators** for a home of this size.

## What size heat only boiler do I need?

Regular and system boilers only have a central heating output as the domestic hot water is stored in a cylinder.

What size combi boiler do you need for your home?

Number of Radiators | Recommended Combi Boiler Size (CH output) |
---|---|

Up to 10 |
24-27 kW |

10-15 |
28-34 kW |

15-20 |
35-42 kW |