Confused by all the boiler types? There are three main types of boiler to choose from in the UK, and choosing the wrong one for your home could cost you money on your energy bills, or mean having to fork out a fortune for unnecessary parts to be installed. But here’s the good news…
Knowing which type of boiler is best for your home really doesn’t have to be rocket science. New boiler installation is one of the most common home improvements as UK homeowners look to upgrade to a more modern and energy efficient boiler. Official figures show that around 1.7 million boilers are installed each year in the UK.
In this article I’m going to explain the three main boiler types in simple terms so that you can make an informed decision when choosing your new boiler.
- Combi Boilers
- System Boilers: The In-Between
- Conventional Boilers: The Old Workhorse
- What Boiler Type Should You Get?
- Things To Consider Before Buying
1. Combi Boilers: The Most Popular Choice
If you ask me, the most obvious question to answer is… which boiler type is most common? The answer is easy: combi boilers. Combi (or combination) boilers are by far the most popular option, as they are small, energy efficient, and provide both heating and hot water from a single compact unit. In fact, 80% of domestic boilers sold in the UK are combi boilers.
Why Combi Boilers Are So Popular
Combi boilers work by heating water directly from your mains supply as soon as you turn on a tap. There is no need for a separate hot water cylinder or cold water tank in your loft.
Advantages
The main advantages of a combi boiler include:
- Instant hot water without waiting for a tank to fill and heat up
- Space-saving design (great for flats and small houses)
- Cheaper to install than other boiler types
- More energy efficient as you only heat the water you need
Sounds great, so what’s the catch…
Disadvantages
Combi boilers can run into problems if you have multiple taps / showers on at the same time. If you’ve got a big family and they all want to shower at the same time in the morning, the water pressure from your combi boiler will drop. They’re also reliant on your mains water pressure. If your water pressure is low, then your combi boiler performance will suffer. If you have more than 2 bathrooms then a combi boiler is likely not the best option for you.
2. System Boilers: The Middle Ground
System boilers are the middle ground between combi boilers and conventional boilers. System boilers use a separate hot water cylinder to store and supply hot water on demand. Unlike conventional boilers, they don’t require a cold water storage tank in the loft – all major components are contained within the boiler unit itself.
How Do They Work?
System boilers heat water and store it in a cylinder until needed. When you turn on a tap, hot water is drawn off the top of the cylinder. This means that multiple taps can be used simultaneously without losing pressure – ideal for larger homes with multiple bathrooms.
Advantages
The benefits of system boilers include:
- Able to supply hot water to multiple outlets at once
- Great choice for homes with more than 2 bathrooms
- No need for loft tank (helps free up loft space)
- Can be fitted with solar thermal panels
- Works well with underfloor heating
Disadvantages
The downsides? You’ll need space for the hot water cylinder – usually in an airing cupboard or utility room. These hot water cylinders are about the same size as a washing machine standing chest-high, so you’ll need to factor that into your space planning.
You also lose a bit of efficiency since you’re storing hot water that gradually loses heat over time. But for homes with families that have high hot water demand, this trade-off is often worth it.
3. Conventional Boilers: The Old Workhorse
Conventional boilers are also known as regular or heat only boilers. Conventional boilers are the traditional ‘system’ of a boiler, hot water cylinder, and a cold water storage tank in the loft. This is the type of system you’ll most often find in older UK properties.
Why Would You Want One?
Truth be told, most people wouldn’t install a new conventional boiler these days. But here are a few situations where they can still make sense:
- Your home already has a conventional system and all the pipework in place
- Your property is an older home with low mains water pressure
- You have very high hot water demand across several bathrooms
Advantages
The main advantage? They’re able to supply lots of hot water to multiple outlets at once.
Disadvantages
The downsides are fairly big though:
- Takes up a lot of space (boiler, cylinder, and loft tank)
- More complex install with higher costs
- Less energy efficient than modern alternatives
- Takes time to reheat hot water once cylinder empties
Conventional boilers are really only suitable for larger properties and are rarely the best choice for most modern UK homes.
4. Which Boiler Type Should You Get?
Now that we’ve looked at the different types, the question is: which boiler type is best for your home? The answer depends on a few factors about your home and lifestyle. Let me explain…
Property Size
First of all, the size of your property matters:
- Small flats and 1-2 bedroom homes? Combi boiler is the way to go.
- Larger homes with 3+ bedrooms and 2+ bathrooms? Look at system boilers
- Only look at conventional boilers if you have a very large property or replacing an existing system
Water Usage
Next, consider your water usage patterns:
- Live alone or with a partner? Combi boiler works well
- Big family where multiple people need showers at the same time? You’ll need a system boiler to store hot water
Space Available
Don’t forget the space available too:
- If you have no loft access and limited storage then combi boilers are compact and wall-mounted
- Got an airing cupboard or utility room? Then a system boiler’s hot water cylinder can fit there
Water Pressure
Water pressure is another thing to keep in mind:
- Check your mains water pressure before getting a combi boiler. If it’s poor, it will show in your performance. Conventional and system boilers don’t depend on mains pressure in the same way.
In short, for most modern UK homes with 1-2 bathrooms, a combi boiler is the sweet spot between efficiency, cost, and performance.
5. Things To Consider Before Buying
Before you commit to a particular boiler type, a few other factors to keep in mind…
Efficiency Ratings
Efficiency ratings are important. From 2025 onwards, all new boilers will have a minimum 92% efficiency rating as the UK government clamps down on poor-performing units. Always aim for A-rated boilers that convert most of your fuel into useful heat.
Installation Costs
Installation costs can also vary widely. Combi boilers are usually the cheapest to install. System boilers cost more as the cylinder needs to be fitted. Conventional boilers are the most expensive unless you’re replacing an existing system.
It’s also worth future-proofing as the UK will phase out gas boilers in all new builds from 2025, with a broader phase-out planned for the mid-2030s. Don’t forget to get a few quotes. The same boiler can cost hundreds of pounds less from one installer vs another.
Installation Quality
And a final thing most people don’t realise… Installation quality is as important as the boiler itself. Always use a Gas Safe registered engineer. A poorly fitted boiler will cost you in repairs and wasted energy much more than buying a cheap option in the first place.
Wrapping It All Up
Picking the right boiler type really doesn’t have to be difficult. Combi boilers make up the majority of boilers installed in UK homes for good reasons: they’re energy efficient, compact, and suitable for most modern homes. System boilers are the middle ground for larger properties. Conventional boilers are only really best for specific situations.
The best choice depends on the size of your home, your hot water usage, the space available, and your mains water pressure. And remember… With around 85% of UK homes on the gas grid, connected to mains sewers, and reliant on boilers to heat water and provide heating, this is one of the decisions as a homeowner that affects your comfort and bills for 10-15 years after you buy.
Choose wisely, install it properly, and you’ll have reliable heating and hot water for years to come.