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Boiler types, from combi boilers to condensing boilers

Boiler types — which boiler is best for your home?

Whatever type of boiler you're thinking of buying or if you just want to find out more about the one you have, our uSwitch boiler guide will help.

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Need help choosing which boiler is best for your home? The first step is choosing your boiler type. Learn more about combi, condensing, conventional boilers and more.

Combi boilers

Combination boilers - more commonly known as combi boilers - are the most popular kind in the UK and provide heat and hot water with no need for water tanks or cylinders. You can pick either a gas or electric combi boiler.


  • You get unlimited heat and hot water when you need it.
  • There's no need for a tank in your loft.
  • They don't take up much space.
  • The water pressure might be reduced if you need hot water from more than one tap at a time.
  • Combi boiler installation is quite tricky.
Suitable for:

Combi boilers are suitable for almost any home, but best for homes where several people aren't likely to need a lot of hot water at the same time.

System boilers

System boilers - also known as sealed system - come with a water cylinder (which usually sits in an airing cupboard) and no water tank.

  • There's no need for a tank in your loft.
  • You can get hot water from multiple taps at the same time.
  • You don't get hot water instantly.
  • The hot water can run out and you'll have to wait for it to reheat.
  • You need to find room for the cylinder somewhere.
Suitable for

Homes which need to have hot water in more than one place at the same time.

Conventional boilers

Conventional boilers - also known as open vent or regular boilers - have both a cylinder and a tank.


You can get hot water from multiple taps at the same time.

  • The hot water can run out and you'll have to wait for it to reheat.
  • You need to find room for the cylinder and the tank.
Suitable for

Homes which need to have hot water in more than one place at the same time.

Condensing boilers

Condensing boilers aren't strictly a boiler type. It's an attribute your boiler can have, e.g., you can have a condensing combi boiler or a condensing conventional boiler.

Condensing boilers are very energy efficient because they capture some of the heat which would escape from the flue of a non-condensing boiler and re-use it.  This means they get more heat from the same amount of fuel, which will save you money on your heating bills.

All modern boilers are condensing boilers.

Energy-efficient boilers

All new boilers are considered energy-efficient, and — for now — must be sold with an energy label (similar to labels on kitchen appliances).

This is a requirement of the Ecodesign for Energy-Related Products regulations.

How else can I save money on heating?

Getting an energy-efficient boiler is a great start to saving on heating, but what's the purpose of heating your home if the heat is escaping?

Boiler guide

Proper insulation and draught-proofing are vital accompaniments to any energy-efficiency upgrades you make on your heating system, and installing them need not be costly or time-consuming.


If you're put off by the invasive nature of insulation installation then draught-proofing is for you. Draught-proofing starts with locating draughts around your home. Look for cracks around windows and doors or gaps between the doors and the frame.

Luckily plugging these gaps is as easy as visiting the DIY store. Self-adhesive foam strips are great for the borders around windows, whilst brushes can be attached to the bottom of doors or letterboxes to stop hot air escaping.

For larger cracks around window frames you can use sealant or putty to fill them up.

For bigger gaps like a chimney flue, you will need specialist products. A chimney balloon simply inflates and blocks the chimney flue, preventing cold air from rushing in and hot air rushing out.


Insulation is more expensive and complex to install, but it's also an even bigger money-saver than draught-proofing, making it well worth the effort.

An estimated 25% of the heat lost in a typical home is through the roof. Loft insulation is the most basic form and if you have a roof and attic in your home, it's where you should start.

While new-build properties and those built in the last few years are likely to already have insulation installed, older properties may not. Even those built in the 70s and 80s may have insulation installed but won't have sufficient levels.

You can buy loft insulation in DIY stores and install it yourself, but you can also have it installed by a professional.

Wall insulation is an even bigger money-saver but has to be installed by a professional, and the type of wall insulation will depend on what type of home you live in.

If your home was built after 1930 the chances are it has cavity walls, meaning an inner and an outer wall. Cavity wall insulation fills the gap between the walls by drilling holes in the outer wall and pumping in insulation.

If your home was built earlier then you most likely have solid walls. Solid wall insulation consists of packing insulation on the inside or outside of the walls and can be expensive to install, but it can also save a lot of money.

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