Is your boiler on its last legs? Or would you just like to replace your old boiler with something more energy-efficient? If so, you need to decide what type of boiler is right for your home.

Heating accounts for about 55% of what you spend in a year on energy, according to the Energy Saving Trust. So choosing the right boiler can make a big difference to your energy bills.

The type of boiler you need depends on lots of things, like the number of people in your household, the size of your home and how many radiators you have. To help you decide what’s best for you, we explain the main types of boiler and the pros and cons of each below.

If you’d like a new boiler, CORGI HomeHeat, part of the OVO family, can take care of everything. Get your fixed price online in just 80 seconds and choose an installation date to suit you. Or call them on 0800 254 5204. One of their local, trusted, Gas Safe registered engineers will carry out the work.

And you can relax with the peace of mind of a parts and labour warranty on all new boilers.

Gas or electric boiler?

Mains gas is competitively priced and generally the cheapest heating fuel available to consumers, according to uSwitch. So it’s no surprise that most homes in the UK have a gas boiler.

If you haven’t got mains gas, one option is an electric boiler for hot water and heating. Electric boilers are usually more compact, more efficient and cheaper to install than gas boiler systems. But a standard unit of electricity (kWh) typically costs at least three times more than a unit of gas, so your heating bills could be much higher than with gas.

Another option for electric heating is night storage heaters, which are designed to make the most of cheaper off-peak electricity tariffs, such as Economy 7.

Many homes without gas have oil-fired boilers for hot water and heating. Modern condensing oil boilers are very efficient and can be cheaper to run than electric systems, but that depends on the price of oil. And if you haven’t got oil central heating already, installing it from scratch can be quite expensive.

If you want to go green, then renewable energy technologies, like heat pumps, biomass boilers and solar panels will help you to do so. Although the costs of installing these systems can be quite high, you could get financial help under the government’s Renewable Heat Incentive.

If you have mains gas and you’d like a gas boiler, there are three main types to choose from: combi, conventional or system.

Main types of gas boiler

1. Combi boilers

Diagram of combi boiler system showing boiler with direct output pipes to a shower, radiators, etc. Combination boilers – better known as combi boilers – are the most popular type of boiler in the UK. They heat hot water directly from the mains when you turn a tap on, so you won’t need a cold water tank or hot water cylinder. They can be an economical choice as you don’t store any hot water – you only heat the water you use.


  • Unlimited heat and hot water whenever you need it
  • Boiler only heats the water you use
  • No need for cold water tank or hot water cylinder


  • Your water pressure may drop if you use more than one hot tap at a time
  • Your water can take a few seconds to heat up, especially if the boiler is a long way from the tap
  • May not work in areas where mains water pressure is low

Good for: Homes with limited space or where you don't have lots of people using hot water at once.

2. Conventional boilers

Diagram of a conventional boiler system showing a boiler with pipes to a cold water cistern, an expansion tank and an insulated hot water cylinder. Conventional boilers – also known as regular boilers – take up more space than combis because they need three tanks:

  • A cold water cistern to store cold water (usually in the loft)
  • A small feed and expansion cistern to maintain the water level of the heating system (usually next to the cold water cistern)
  • An insulated cylinder to store hot water (often in an airing cupboard)

With a conventional boiler, you'll be able to run hot water from more than one tap at a time without a significant drop in pressure. But when the hot water runs out, you'll have to wait for it to heat up again.


  • Hot water from several taps at once
  • Works even in areas where water pressure is low


  • You need to wait for water to reheat if hot water runs out
  • You need space for the cold water tank and hot water cylinder

Good for: Homes where a lot of hot water is used at the same time.

3. System boilers

System boilers – or sealed system boilers – work in a similar way to conventional boilers. The difference is that they don’t need a cold water tank, so they’re simpler to install and take up less space.


  • Hot water from several taps at once
  • More compact than conventional boiler systems


  • You need to wait for water to reheat if hot water runs out
  • You need a hot water cylinder

Good for: Homes with less space where a lot of hot water is used at the same time.

What about energy-efficient condensing boilers?

In the UK all newly installed gas boilers (with a few rare exceptions) must be condensing boilers. So whether you choose a new combi, conventional or system boiler, you’ll have an energy-efficient boiler.

Condensing boilers are very energy efficient because they capture and reuse some of the heat that would otherwise escape from the flue.

That means you could really save money on your heating bills. The Energy Saving Trust estimates that you could save up to £305 a year on heating with a modern condensing boiler, depending on how old your existing boiler is.

Find out more about boiler efficiency.

So which boiler should I get?

Choosing a boiler involves more than just weighing up the pros and cons above. To help you make up your mind, see our guide to choosing the right boiler for your home.

You may also like to know more about heating controls and radiators, as this can also affect your choice of boiler and central heating system.

As everyone's situation is different, it's always good to get advice from a professional installer. CORGI HomeHeat (or call 0800 254 5204) is there to help.