If your boiler is getting old or you’re planning a renovation, one of the first questions is which type of boiler you actually need. There are three main types in UK homes: combi, system and regular (also called heat-only or conventional) boilers. Each works differently, and the right choice depends on your home, how much hot water you use, and the system you already have.
Here’s a straightforward guide to how each one works and who it suits.
Combi Boilers
A combination (combi) boiler heats water directly from the mains whenever you turn on a tap, and provides your central heating from the same compact unit. There’s no hot water cylinder and no tanks in the loft.
Advantages
- Compact, freeing up space where a cylinder or loft tanks used to be
- Hot water on demand, so it never runs out
- No energy wasted keeping a tank of water hot
- Usually the simplest and quickest type to install
Things to consider
- Flow can drop if several taps or showers run at once
- Performance depends on your mains water pressure
- No hot water cylinder, so no immersion heater as a backup if the boiler breaks down
Best for: flats and small to medium homes with one bathroom, or one bathroom and an en-suite.
System Boilers
A system boiler heats water and stores it in a hot water cylinder, usually kept in an airing cupboard. Most of the main system components are built into the boiler itself, so there are no tanks in the loft.
Advantages
- Supplies several taps and showers at the same time without a drop in flow
- No loft tanks, which reduces the risk of freezing and frees up loft space
- The cylinder can often be fitted with an immersion heater as a backup
Things to consider
- You need space for a hot water cylinder
- Stored hot water can run out, and takes time to reheat
Best for: larger homes with two or more bathrooms, where several people may need hot water at the same time.
Regular Boilers
A regular boiler works with a hot water cylinder and two tanks in the loft: a cold water storage tank and a smaller feed and expansion tank. This is the traditional setup found in many older UK homes, and it’s what’s known as an open-vented system.
Advantages
- Handles high hot water demand across several bathrooms
- Works well where mains water pressure is low
- Often the least disruptive option if you already have one, since the existing pipework can stay
Things to consider
- Takes up the most space, with tanks in the loft and a cylinder elsewhere
- Loft tanks can be vulnerable to freezing in winter
- Water pressure is generally lower unless a pump is added
Best for: larger or older homes with an existing regular system, or areas with low mains pressure.
At a Glance
| Combi | System | Regular | |
|---|---|---|---|
| Hot water cylinder | No | Yes | Yes |
| Loft tanks | No | No | Yes |
| Space needed | Least | Medium | Most |
| Several outlets at once | Limited | Good | Good |
| Typical home | 1 bathroom | 2+ bathrooms | Older, larger homes |
Can You Switch Boiler Type?
Yes, and many people do when replacing an old boiler. The most common change is from a regular boiler to a combi, which removes the loft tanks and hot water cylinder altogether and frees up a surprising amount of space.
It isn’t always the right move, though. A combi needs good mains water pressure and flow, and older pipework that has been used to a low-pressure system can sometimes develop leaks when a system is converted. A proper assessment before any work starts is essential.
It’s also worth thinking longer term. If you might consider an air source heat pump in future, bear in mind that heat pumps work with a hot water cylinder, so removing yours now could mean fitting one again later.
How to Choose
The right boiler comes down to a few key questions:
- How many bathrooms do you have? One usually suits a combi; two or more often suits a system boiler
- How many people use hot water at the same time?
- How much space do you have for a cylinder or tanks?
- What’s your mains water pressure like?
- What system do you have now, and how old is the pipework?
Get Expert Advice
Choosing the wrong type of boiler can mean years of poor hot water performance, so it’s worth getting advice from someone who has seen your home. Our Gas Safe engineers will look at your property, check your water pressure and existing system, and recommend the boiler that genuinely suits you, not just the one that’s easiest to fit.
We install boilers from leading manufacturers including Worcester Bosch, Vaillant, Baxi and Main, for homes across Preston, Chorley and the wider North West. Find out more about our boiler installation service, call us on 01772 426 065 or get in touch for a free, no-obligation quote.