What is a combi boiler?


What is a combi boiler and how does it work?

A combi (or combination) boiler is a high-efficiency water heater and a central heating boiler, combined within one compact unit. Hot water is provided on demand rather that stored in a water tank meaning you can have a nice hot shower, run a long bath or have the heating on all day wihtout having the worry of running out of hot water.

Why you should choose a combi?

Perfect for homes that are short of storage space as you do not need any water tanks or cylinders
Highly efficient when compared to older boiler models.
Installation costs are typically cheaper than standard or system boiler

Why choose a Worcester Bosch combi boiler?

Worcester Bosch boilers have won Which? Best buy for gas boilers for the last 9 years running highlighting the quality, energy efficiency and all round performance of the full Worcester Bosch range. To read more about Worcester Bosch and Which? visit:https://www.worcester-bosch.co.uk/products/boilers/which-best-buys


What are the disadvantages of a combi?

  • Not ideal for homes with low water pressure
  • Cannot deliver a high capacity of hot water to multiple outlets e.g. two showers
  • Not suited to larger households
  • Power showers cannot be installed with these boilers

Is a combi boiler cheaper to run?

The Energy Saving Trust says whether a combi or a standard boiler is cheaper to run depends completely on your lifestyle.

A combi boiler is more economical to run as a result of not needing a hot water tank, which helps to keep costs down. They are cheaper to run if your household doesn’t use too much water. Combi boilers can be more efficient as they don’t leave water sitting in a tank where it can lose heat, instead the water gets put to use when needed.

Regular boiler for example, tends to produce hot water twice a day, regardless of if it gets used or not – in the morning and in the evening. This requires the boiler to fire up to produce the hot water, if it doesn’t get used the water simply cools down, which will waste energy over time.

I don't have a combi boiler, should I switch?

If you have a small to medium-sized house where space is at a premium, then combi boilers are a fantastic choice due to their compact size. Some models are even small enough to fit in a standard kitchen cupboard.

What size combi boiler do you need?

KW output Bedroom Radiators
24 - 27Kw 1 - 2 bedrooms 10 Radiators
28 - 34Kw 3 - 4 bedrooms 15 Radiators
35 - 42Kw 4+ bedrooms 20 Radiators

There are many factors that you need to consider when choosing the right boiler for your home, e.g. number of bath and showers. The above table should be used as a guide but please be aware you might need a different sized boiler based on your lifestyle.

How much does a combi boiler cost?

  • Swapping your existing combi with a new one – starting from £1,695 + VAT (labour & parts)
  • Converting from a Standard, system or back boiler to a Combi boiler – starting at £2,425 + VAT (labour & parts)

Included within your fixed price

  • Gas Safe installation
  • FREE Honeywell Smart Thermostat RRP £199.99
  • FREE Worcester Bosch magnetic filter worth £154.99
  • FREE system cleanse
  • Up to a 10 year guarantee
  • Flue worth up to £100
  • Fitting pack
  • All the right safety attachments

If you would like to replace your boiler or just get a genuine fixed price visit