Choosing the right boiler for your home doesn't have to be complicated. Whether you're replacing an old system or installing heating for the first time, understanding the three main boiler types makes it easier to select one that matches your property's needs.
The type of boiler you choose affects everything from your energy bills to how quickly you get hot water. Each system has distinct advantages and works better in different situations. Some are perfect for small flats, while others excel in larger family homes with multiple bathrooms.
This guide breaks down everything you need to know about combination, conventional, and system boilers. By the end, you'll understand which boiler type heating system works best for your specific needs and budget.
- Content Guide
- » Boilers and Their Operation
- » Choosing the Right Boiler for Your Home
- » Should You Stick With the Same Type?
- » The 3 Types of Boiler You Need to Know
- - Combination Boilers
- - Conventional Boilers
- - System Boilers
- » What is a Hydrogen-ready Boiler?
- » Things to Consider When Choosing the Right Boiler Type
- - Household Size and Usage
- - Available Space
- - Water Pressure
- - Budget Considerations
- » Making Your Final Decision
Boilers and Their Operation
Most UK homes connect to mains gas for a constant fuel supply, though some properties use oil, LPG (liquid petroleum gas), or alternative heating sources like heat pumps.
The basic operation remains consistent across all types of boilers. When your boiler runs, a valve opens to allow gas entry. This gas burns to create hot flue gases, which heat water pumped through the boiler. An electric pump then sends this hot water to radiators, taps, and showerheads throughout your home.
While the fundamental process stays similar, each boiler type operates slightly differently. Understanding these differences helps you identify the most suitable option for your property.
A safe, efficient home starts with a professional boiler installation.
Choosing the Right Boiler for Your Home
Picking the right boiler can feel confusing, but it really comes down to two simple questions: What type of boiler do you have now, and how much hot water does your household actually use?
Spotting Your Boiler TypeYou can usually work this out just by looking at the boiler itself and the setup in your home:
- Combi Boilers – Compact units with 5–6 copper pipes underneath and no external pump. Ideal for flats or smaller houses where space is tight.
Check out our blog post on ‘Combi vs Conventional Boiler’ for a clear comparison. - System Boilers – Typically 3–4 copper pipes and paired with a separate hot water cylinder (but no loft tank). Perfect for larger homes with multiple bathrooms.
- Regular (Conventional) Boilers – Often with two pipes at the top and one at the bottom. These need both a hot water cylinder and a tank in the loft, so they're usually found in bigger houses with older heating systems.
- Smaller homes or flats: A combi boiler usually makes the most sense. It's efficient, compact, and doesn't need a tank.
- Bigger houses with two or more bathrooms: A regular (conventional) boiler is often the best choice. It can handle high demand, but it does need more space for tanks.
- Homes with high demand but limited loft space: A system boiler strikes a balance—hot water cylinder but no loft tank.
Should You Stick With the Same Type?
In many cases, yes.
Replacing your boiler with the same type keeps things simple (and cheaper), since your existing pipework and tanks are already set up that way. Swapping to a different style of boiler often means extra plumbing work and higher costs.
The 3 Types of Boiler You Need to Know
Combination Boilers
A combination (combi) boiler generates both heating and hot water from a single, compact unit. This compact design removes the need for a separate hot water tank, which is why it's the most common choice in UK homes.
How do Combination Boilers Work?
Combi boilers connect directly to your mains cold water supply and heat water on demand. When you turn on a hot tap, the boiler ignites and uses an integral heat exchanger to instantly heat cold water flowing through the system.
| Advantages | Disadvantages |
|---|---|
| Space efficient – no separate water tank required | Pressure dependent – poor mains pressure affects performance |
| Instant hot water – no waiting for tanks to heat up | Single-use limitation – water pressure drops when multiple taps run simultaneously |
| Energy efficient – modern models achieve over 90% efficiency | No power shower compatibility – requires a gravity-fed system |
| Easy maintenance – popular design means most engineers can service them | More components – additional moving parts increase potential failure points |
| Cost-effective – generally cheaper to install and maintain | Solar system incompatibility – most models don't work with solar water heating |
| Fresh water supply – hot water comes straight from the mains |
Is a Combi Boiler Right for You?
The best combination boiler suits properties with:
- Small households (1-3 people)
- One bathroom
- Limited storage space
- 10 radiators or fewer
- Good mains water pressure
Conventional Boilers
A conventional boiler, also called a regular or heat-only boiler, is the classic type of heating system used in many UK homes.
These boilers heat radiators directly and require a separate cylinder or tank for hot water storage.
How Conventional Boilers Work?
Like combi boilers, conventional systems use a heat exchanger to warm water when fuel ignites. However, a pump transports heated water to a storage tank rather than supplying it directly. This stored hot water flows to radiators for heating or to taps when needed.
| Advantages of Conventional Boilers | Disadvantages |
|---|---|
| Multiple simultaneous use – hot water flows from several taps at once | Delayed hot water – requires time for cylinder heating |
| Solar system compatibility – works with renewable energy systems | Lower efficiency – heat loss from stored water reduces overall efficiency |
| Backup options – immersion heaters provide hot water if the boiler fails | Higher installation costs – more expensive if tanks aren't already present |
| Low pressure tolerance – suitable for properties with poor mains pressure | Space requirements – needs room for boiler, hot water cylinder, and expansion tanks |
| Cost-effective replacement – typically cheaper to replace existing conventional systems | Limited capacity – the hot water supply is finite until the tank refills |
Is a Conventional Boiler Right for You?
The best conventional gas boiler works well in:
- Larger households (4+ people)
- Properties with multiple bathrooms
- Homes with low mains water pressure
- Older properties with existing tank systems
System Boilers
System boilers combine elements of both conventional and combi systems. They require a hot water cylinder, but eliminate the need for a cold water tank. Key components like pumps and valves integrate into the main unit rather than being separate elements.
How System Boilers Work?
System boilers operate similarly to conventional boilers but with integrated components. Think of them as the modern upgrade to traditional conventional systems, offering improved efficiency and easier installation.
| Advantages | Disadvantages |
|---|---|
| Space saving – integrated components and no cold water tank | Pressure dependent – relies on good mains water pressure |
| Reduced complexity – fewer separate components to maintain | Hot water cylinder required – still needs storage space |
| Faster installation – quicker to fit than conventional systems | Modern system requirements – works best with updated central heating systems |
| No loft components – eliminates freezing and leak concerns in roof spaces |
Is a System Boiler Right for You?
System boilers suit properties where conventional boilers work well, particularly if you have:
- Good mains water pressure
- Modern central heating systems
- Space for a hot water cylinder, but limited loft space
Visit our blog’s boiler reviews section to help you make an informed choice.
What is a Hydrogen-ready Boiler?
A hydrogen-ready boiler is a new type of boiler designed to run on either natural gas or 100% hydrogen. It functions in the same way as your current gas boiler to heat your home, but uses a significantly cleaner fuel source.
You can install a hydrogen-ready boiler today and run it on your existing natural gas supply.
Thinking about upgrading? Find out in our blog: ‘When Should I Replace My Boiler?’.
Things to Consider When Choosing the Right Boiler Type
Your ideal boiler depends on several factors, including property size, household needs, and existing infrastructure. Consider these key questions:
Household Size and Usage
Small households with one bathroom benefit most from combi boilers. Larger families with multiple bathrooms need the capacity of conventional or system boilers.
Therefore, don’t overlook the boiler size and kW capacity of your boiler; this directly affects its ability to meet your home’s heating demands.
Available Space
Limited space favours combi boilers. Properties with existing tank systems or adequate storage space can accommodate conventional or system boilers.
Water Pressure
Good mains pressure suits combi and system boilers. Poor pressure makes conventional boilers the better choice.
Budget Considerations
Factor in both installation and running costs. While combi boilers often cost less initially, conventional systems might be cheaper if you're replacing an existing similar system.
Making Your Final Decision
Understanding all types of boilers helps you make an informed choice, but a professional assessment ensures the best outcome. A qualified heating engineer can evaluate your property's specific requirements, existing infrastructure, and usage patterns. Growing families might outgrow a combi boiler, while downsizing households could benefit from switching to a more compact system.
Ready to upgrade your heating system?
Contact our certified gas heating engineers for a comprehensive boiler assessment and personalised recommendations tailored to your London property.
