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24th February, 2025

What Type of Boiler Do I Have?

What Type of Boiler Do I Have?

Key takeaways

  • Combi, system, and regular boilers differ by how they store hot water.
  • You can convert a regular boiler to a combi if your mains pressure is sufficient.
  • Larger homes with multiple bathrooms often benefit from system or regular boilers.
  • Try a new boiler quote, finance available including 0% APR.

Despite over 22 million UK homes having gas central heating, a great deal of homeowners are unsure about which type of boiler they have installed in their homes.

Knowing the type of boiler you have can come in incredibly handy, especially if any problems arise that need to be fixed by an engineer or if you’re getting your old boiler replaced.

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When you get a quote on a brand new boiler with iHeat, we ask you a few questions about your home.

One of these questions is ‘What type of boiler do you currently have?’ This helps us to work out how big the job is likely to be and allows our engineers to be better prepared.

That’s why we’ve put together this handy guide to help you determine which type of boiler you currently have in your home. We’ll be taking a look at the different types of gas boilers: combi, system and regular, their advantages and disadvantages, as well as some tips on how to identify your boiler type.

Combi Boilers

A combination or ‘combi’ boiler is a gas boiler that combines a water heating system and a central heating unit into a single body to produce hot water instantly, meaning there is no need for a separate hot water tank.

As you’re combining two different boilers into one body, they take up much less room in your home than system or regular boilers, making them ideal for smaller homes where space and storage is an issue.

Another great benefit of a combi boiler is its efficiency. By heating water on demand as opposed to constantly heating stored water, you can save energy and cut costs on your fuel bills.

A new combi boiler should be around 90% efficient, so replacing your old boiler could save you up to £380 on gas bills according to The Energy Saving Trust.

Do I Have a Combi Boiler?

On a combi boiler there will be five copper pipes coming from the bottom and there will be no external pump or hot/cold water cylinders as the heating components are combined into a single unit.

You’ll most likely find a combi boiler in small/medium-sized homes with a lower demand for hot water.

System Boilers

System boilers heat your central heating system and produce hot water for a water storage cylinder, directly taking their water from the mains as opposed to using a feed and expansion tank like a regular boiler.

These are usually found in homes that have a high demand for hot water.

System boilers offer a number of advantages such as the fact they can provide hot water to two bathrooms at once without affecting the heating of your home and they don’t require a cold water tank.

The drawbacks, of course, are that you’ll need enough room to store the large hot water tank, so these boilers are usually unsuitable for flats or smaller homes.

Another disadvantage is that once the hot water from the tank has been used up, you’ll need to wait for it to refill and heat the water again before getting any more hot water.

Do I Have a System Boiler?

You can usually tell if you have a system boiler by taking a quick look at it. Normally, there will be three copper pipes coming from the bottom of the boiler (as opposed to five with a combi). You should also be able to see a hot water cylinder but there won’t be any external pump for expansion storage.

You’ll most likely find a system boiler in larger homes that have a higher demand for hot water from multiple outlets at once.

Regular Boilers

Regular boilers are also known as conventional or heat only boilers because they don’t provide domestic hot water on demand the same way combi boilers do. They instead store hot water in a cylinder until it is required to be delivered to a tap or shower.

An advantage of this is that they can meet a high demand for hot water at once, making them ideal for properties with multiple bathrooms, though when the water does run out, you'll have to wait for it to fill up again in the same way you would a system boiler.

Another disadvantage is that regular boilers require both a hot and cold water storage tank which can take up a lot of space in your home.

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Do I Have a Regular Boiler?

You can usually tell if you have a regular boiler by taking a quick look at it. Normally, there will be two copper pipes coming from the top of the boiler and just one coming from the bottom.

Regular boilers also have hot water cylinders and a cold water storage tank which can usually be found in the loft. There should also be an external pump, unlike with combi or system boilers.

Similar to a system boiler, you’ll most likely find a regular boiler in larger homes that have a higher demand for hot water from multiple outlets at once.

For more information and advice, why not check out some of our other helpful blogs or take a look at some of our most Frequently Asked Questions! If you’re still struggling to identify your type of boiler, please don’t hesitate to get in touch with one of our friendly team members at iHeat who will be happy to help.

Can My Conventional Boiler Be Converted To A Combi?

Yes, it is possible to have your conventional boiler converted into a more efficient combi heating system by a qualified engineer.

But first, some due diligence needs to be carried out, combi’s run off the mains water supply, so you need to first ensure the pressure from your cold tap is sufficient. The specific reason the cold tap is crucial is that often system and heat only boilers have pumps on the showers to increase pressure. If a conventional boiler is converted to a combi boiler, these pumps will be removed along with the hot water tanks many conventional boilers use.

How iHeat Can Help

Here at iHeat we stock a range of sleek, modern boilers that can save you money on your heating bills while keeping you warm and toasty. Or for more information and advice, why not check out some of our other helpful blogs or take a look at some of our most Frequently Asked Questions!

 If you’re still struggling to identify your type of boiler, please don’t hesitate to get in touch with one of our friendly team members at iHeat who will be happy to help.

Get a free fixed price quote for a new boiler installed fast! - Find the perfect boiler!

Get a quote

Frequently Asked Questions

How Do I Know What Boiler I Have?

Check your boiler casing or behind the control panel for any labels indicating the manufacturer and basic details. Often, you’ll find “combination,” “system,” or “regular” in the product name. You can also refer to past service records or the original manual to confirm the type.

How Do I Know What Model Boiler I Have?

Locate the data plate or specification sticker on the inside panel or side of the unit. This should display the boiler model and serial number. If it’s missing or unclear, you can search the manufacturer’s website or consult a heating professional, providing any visible serial code to help identify the exact model.

What Are the Three Types of Boilers?

Combi (combination) boilers supply hot water on demand without a storage tank. System boilers use a separate hot water cylinder but don’t require a cold water tank. Regular (heat-only) boilers require both a hot water cylinder and a cold water storage tank, often found in older or larger homes.

Do I Have a Gas or Combi Boiler?

Combi boilers typically run on gas and provide instant hot water without a separate storage cylinder. If your unit heats water only when you turn on a tap, you probably have a combi. If you see a separate hot water cylinder, it’s likely a system or regular gas boiler.

How to Tell If a Boiler Is Gas or Electric?

A gas boiler usually has a gas line running in and a flue pipe that vents combustion gases outside. An electric boiler doesn’t require a flue or gas piping; it relies solely on your home’s electrical supply and is generally smaller, with no visible gas burner components.

What Is the Difference Between a Combi System and a Regular Boiler?

A combi system heats water on demand and needs no hot water cylinder, making it compact and efficient for smaller homes. A regular (heat-only) boiler needs both a hot water cylinder and a cold water storage tank, suitable for larger properties or traditional gravity-fed setups.

Does a Combi Boiler Use Electricity or Gas?

Most UK combi boilers run primarily on gas, but they do require a small amount of electricity to power internal components such as the pump and control panel. Fully electric combi models are less common and are generally used where there is no gas supply available.

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Article by
Stephen Day

Co-founder

Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.