Boiler types: how to choose the right boiler

Thinking about updating your boiler and heating system ready for the cold winter months? Read our expert advice for everything you need to know about boilers before you invest…

Boilers: what are the main different types of boiler available and which should I choose?
Published: November 9, 2021 at 12:57 pm
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Heating and hot water are essential for our homes, and if your system isn’t performing as well as it should, now could be the time to think about replacing it. The latest models are much more efficient and better for the environment, so it’s definitely a worthwhile investment.


Consider your existing fuel type, how many people will be needing hot water and if you’re a bath or shower household, as this will determine how much hot water you’ll be needing day to day.

What are the main types of gas boiler available? Combination or ‘combi’ boilers

Combi boilers

Combination or ‘combi’ boilers are the most popular option in the UK, providing heat and hot water without the need for a water tank or cylinder. These are generally available in both gas or electric models. They don’t need much space and provide unlimited heat and hot water on demand, although hot water pressure is likely to drop if you need to use more than one hot tap at the same time.

System boilers

System boilers require a water cylinder – often sited in an airing cupboard – but no water tank. You can get hot water from multiple taps at the same time, but the hot water isn’t instant and you will have to wait for it to reheat if the hot water runs out.

Conventional boilers

Conventional boilers have both a cylinder and a tank, and they’re also known as open vent or regular boilers. You may sometimes have to wait for the water to reheat, and you will need to have space for both the cylinder and the tank.

Condensing boilers

Condensing boilers are not a separate type of boiler in themselves, but an attribute that most modern boilers have. They capture some of the heat that can escape from the flue of a non-condensing boiler and reuse it, making them more energy efficient.

Jonathan Kidner, Product Engineer at Alpha Heating Innovation, recommends that the most important thing to consider when choosing a new boiler is the hot water and heating demand in your household. ‘Do you have a small property and a low demand for hot water and heat, or do you have a busy household with multiple bathrooms and more than one shower in operation at the same time? Think about whether you have built an extension or added more bathrooms since the previous boiler was installed, or whether you are planning future extensions or room conversions, as these scenarios could mean larger output requirements.’

What types of fuel are available to heat my home?

Depending on your home and your requirements, there’s a wide range of fuels that can be used to provide heating and hot water, usually through a boiler. Although natural gas is most commonly used in the UK, it’s not necessarily the best choice for every household.

Natural gas

Gas boilers are fuelled by natural gas, which is delivered via the mains to our homes. However, around 4 million rural homes in the UK do not have access to the mains.


A popular alternative for homes that are not connected to the gas mains, oil is stored in a tank located close to your property. This oil must be ordered in advance so it’s important to be aware of when you are running low.


Liquid petroleum gas (LPG) is another option for homes without a gas supply. LPG storage tanks come in a range of sizes, and are refilled either by tanker, or often from smaller cylinders or bottles which can be replaced when empty.


Homes that are not connected to gas may consider an electric boiler, especially if an oil tank isn’t practical. They essentially work like a kettle, but on a much larger scale. They’re often more suited to smaller homes because they can only heat a limited amount of water at a time.

Darren McMahon, Marketing Director at Viessmann, recommends that the alternative closest to mains gas, for use with a boiler, is LPG. ‘This is compatible with Viessmann’s conventional gas-condensing boilers. BioLPG is a more eco-friendly option that uses propane produced from renewable materials and can reduce CO2 emissions by up to 80 per cent. Electricity and oil tend to be more expensive than gas, too. Renewable heating is a great option for off-grid properties, either exclusively, if the house is well-insulated, or as part of a hybrid system where a renewable heating product can be matched with a boiler to provide the best of both worlds.’

How much does a new boiler cost and how much money could I save by replacing my old boiler?

Typically, a straightforward gas boiler replacement plus thermostatic radiator valves will cost from about £2,500, excluding radiators.

However, according to The Energy Saving Trust, if you replace your existing model with an efficient A-rated boiler and set of heating controls you could save over £300 and 1,500kg of carbon emissions a year - meaning the upgrade could pay for itself in just over eight years.

‘If your boiler is around 10-15 years old and coming to the end of its service life, you will be much better off replacing it with a new, high-efficiency model,’ says Jonathan Kidner, Product Engineer at Alpha Heating Innovation. ‘If your boiler is having to work harder than necessary to heat your home and water, it is likely to be pushing up your heating bills.’

Are there any government grants available to help towards the cost of a new boiler?

ECO is a scheme supporting energy efficiency improvements, including insulation and some heating systems in low income and vulnerable households. It’s not a government grant, but an obligation on large energy suppliers to support households. You may qualify if you claim certain benefits and meet other requirements. If there is a specific scheme in your area you may be able to get help even if you’re not receiving any benefits.

If you install a renewable heating system, you may be eligible for RHI – a government scheme where you can be paid for every unit of renewable heat you produce for a number of years. For more details visit

Are there any more eco-friendly alternatives to a boiler?

Choosing a renewable energy system will reduce your energy bills and benefit the environment. Renewable technologies include ground source and air source heat pumps, solar water heating, biomass boilers and thermal energy stores.


‘Heat pumps are a great sustainable solution as they emit zero emissions, making them carbon neutral at point of use,’ says Mark Wilkins, Technologies and Training Director at Vaillant. ‘Heat pumps use heat energy from the environment around them, such as the ground or air, to create central heating in your home. Electricity is used to power the heat pump, but for every 1kW of electricity used by the pump you can get up to 5kW of heat in return.’


Lisa Hibberd is an experience freelance journalist specialising in interiors


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