Boilers remain the heart of most UK home heating systems—even as low-carbon alternatives like air source heat pumps and hydrogen-ready solutions continue to gain traction in government policy and consumer interest. Despite the gradual shift toward renewable energy, the vast majority of UK homes still rely on gas, oil, or electric boilers for both central heating and hot water. With more than 23 million households using boilers as their primary heat source, understanding the range of different kinds of boilers available has never been more relevant.

In 2025, choosing the right boiler is no longer a one-size-fits-all decision—or simply about opting for the cheapest model on the market. Instead, it requires a careful evaluation of your home’s specific needs. Factors such as household size, number of bathrooms, water usage habits, available space, and the condition of your existing heating system all play a crucial role in determining the most suitable boiler type. In an age where energy efficiency and running costs are top concerns for homeowners, making the wrong choice could lead to poor performance, inflated energy bills, or unnecessary installation expenses.

The market offers a range of options, from the highly popular combi (combination) boiler—favoured for its space-saving design and on-demand hot water—to more traditional setups like heat-only (or regular) boilers, ideal for older homes with existing cylinder systems. System boilers offer a middle ground, providing stored hot water without the need for a loft tank. Then there are electric boilers and hybrid solutions designed for properties off the gas grid, as well as modern condensing models that maximise energy efficiency.

This in-depth article breaks down the different types of boilers currently available in the UK, explaining how each one works, who they’re best suited for, and what to consider before buying. Whether you’re replacing an outdated model or upgrading for better efficiency, this guide will help you navigate the options different kinds of boilers with confidence and clarity.

Combi (Combination) Boilers

Overview:
Combi boilers combine both central heating and hot water in one compact unit, making them extremely space-efficient and easy to install, especially in smaller homes or flats. They heat water on demand—no tanks or cylinders required.

Advantages:

• Instant hot water at mains pressure

• No need for loft or cupboard space

• High efficiency (often A-rated condensing models)

Limitations:

• Not ideal for households with simultaneous usage (e.g., baths + showers)

• Less effective in low mains water pressure areas

Ideal for:
Couples or small families living in flats or homes with limited space and moderate hot water demand.

System Boilers

Overview:
System boilers heat water ahead of time and store it in a hot water cylinder. Unlike combis, they don’t require a loft-based cold water tank. Many core components—like the pump and expansion vessel—are built into the boiler casing.

Pros:

• Delivers hot water to multiple taps at once

• Better suited to homes with high water demand

• Compatible with solar thermal systems

Cons:

• Requires space for the hot water tank

• Hot water supply can run out and requires reheating

Ideal for:
Mid-sized to larger households with multiple bathrooms and moderate mains water pressure.

Heat-Only (Regular/Conventional) Boilers

Overview:
Also called ‘traditional’ or ‘regular’ boilers, these systems use a cold water tank (typically in the loft) and a hot water cylinder. The boiler heats water which then circulates through both storage and radiator systems.

Pros:

• Suitable for larger homes or buildings needing simultaneous hot water

• Works well in low mains pressure areas

• Allows for backup heating via immersion heater in cylinder

Cons:

• Occupies more space (tanks + boiler + cylinder)

• Less efficient than combi boilers due to heat loss from stored water tanks

• Requires longer to reheat hot water once depleted

Ideal for:
Older, larger homes with traditional heating systems or low mains water pressure.

Electric Boilers & Storage Combi Boilers

Electric Boilers

These run purely on electricity and are flue-free, making them suitable for homes with no gas supply, such as flats or older properties. They’re quiet, compact, but running costs can be higher unless paired with renewable energy.

Storage Combi Boilers

Less common than other types, storage combis combine a small internal water cylinder with a traditional combi design. They provide instant hot water at multiple taps while still saving loft space, offering a hybrid between combi and system boilers.

Condensing vs Non‑Condensing Boilers

All modern boilers sold in the UK are condensing boilers, by law. Condensing technology recovers heat from flue gases, improving efficiency significantly—up to 90%+.

Why it matters:

• Non-condensing boilers are largely phased out

• Serving higher efficiency reduces energy bills and emissions

• Proper installation and correct flow temperature settings (e.g., heating at ~70 °C) are essential for condensing operation

Other Boiler Types

Back Boilers

Installed behind existing fireplaces or stoves. These older units use stove heat to warm water, offering a dual-purpose, space-saving solution. Scarce today but still found in older UK homes.

Biomass Boilers

Burn wood pellets or logs. Suited for rural, off‑grid homes, biomass boilers qualify for government renewable heating grants—but involve maintenance and fuel storage logistics .

Choosing the Right Boiler: Key Considerations

*(System boilers supply stored hot water but with a cylinder delay.)

Selecting the best boiler depends on family size, hot water demand, available space, mains water pressure, and future upgrades like solar heating. Remember, combining with insulation upgrades and proper service improves efficiency substantially.

Conclusion

In 2025, UK households can choose from a range of well‑established boiler types: combi boilers for compact, efficient heating; system boilers for high water demand; heat-only boilers for traditional systems; plus electric and storage combi options. All new boilers must be condensing models, offering top efficiency when properly installed and maintained.

Which boiler suits you best depends on space, hot water demand, existing heating infrastructure, and long-term energy efficiency goals. If you’re unsure, consulting a Gas Safe engineer for a tailored assessment based on household profile is always smart.