Choosing a new boiler is one of those decisions that affects your home for the next 10-15 years, so it’s worth getting right. The good news is that once you know your household’s hot water needs and your property’s setup, the choice becomes pretty straightforward.
This guide walks through the main boiler types, what suits different homes, and what to consider before making a decision.
The three main boiler types
Combi boilers
A combi boiler (combination boiler) heats water directly from the mains when you turn on a tap or shower. No hot water tank, no cold water tank — everything is heated on demand.
Best for:
- Small to medium homes (1–3 bedrooms)
- Properties with limited space
- Households where only one shower/tap is used at a time
Not ideal for:
- Homes with multiple bathrooms being used simultaneously
- Properties with low mains pressure
Combis are the most common choice for replacements because they’re compact, efficient, and usually the simplest to install. See: Boiler Installation
System boilers
A system boiler works with a hot water cylinder (usually in an airing cupboard). It heats water and stores it, so multiple taps/showers can run at once without losing pressure.
Best for:
- Larger homes (3+ bedrooms)
- Multiple bathrooms
- Homes where several people need hot water at the same time
Not ideal for:
- Small flats or homes with no space for a cylinder
System boilers are a good middle ground — they don’t need a loft tank like older systems, but they still give you stored hot water.
Conventional boilers (regular/heat-only)
A conventional boiler (also called regular or heat-only) works with both a hot water cylinder and a cold water tank, usually in the loft.
Best for:
- Older properties already set up this way
- Homes with gravity-fed systems
- Properties with low mains pressure where a system boiler wouldn’t work well
Not ideal for:
- Homes without loft space
- Anyone looking to save space or simplify the setup
Most modern replacements move away from conventional boilers unless there’s a specific reason to keep the existing setup.
How to choose the right size boiler
Boiler output is measured in kilowatts (kW), and choosing the right size depends on:
- Number of radiators
- Property size
- Hot water demand
Rough guide:
- 1–2 bedroom flat: 24–28 kW combi
- 3 bedroom house: 28–35 kW combi or 18–25 kW system boiler (with cylinder)
- 4+ bedroom house: 35+ kW combi or system boiler with appropriately sized cylinder
An undersized boiler won’t keep up with demand. An oversized one wastes energy and can cost more to run. A proper heat loss calculation (which any decent installer should do) gives you the right answer. See: Boiler Installation in Middlesbrough
What about efficiency?
Modern boilers are all pretty efficient — most are rated A-rated and achieve around 90%+ efficiency. The difference between brands at this level is usually more about build quality, warranty, and reliability than the efficiency number itself.
Look for:
- ErP A-rating (standard for new boilers)
- Boilers that qualify for any available government schemes (if applicable)
- Brands with good parts availability and support
Should you consider a power flush?
If you’re replacing an old boiler, it’s often worth getting a power flush done before the new one goes in. This clears out sludge and debris from the heating system, which can otherwise shorten the life of the new boiler.
See: Power Flushing
What about radiators?
If your radiators are old, undersized, or not heating properly, it’s worth addressing that at the same time as the boiler. A new boiler won’t fix radiators that are blocked or too small for the room.
See: Radiators
Getting the installation right
The boiler itself is only part of the job. Proper installation includes:
- Correct sizing and positioning
- Upgrades to pipework/controls if needed
- Flushing and balancing the system
- Registering the warranty and issuing the required certification
A good installer will also talk you through what to expect, how long the job will take, and what disruption there’ll be. See: Boiler Servicing for ongoing maintenance.
How much does a new boiler cost?
Budget roughly:
- Combi boiler replacement: £1,800–£3,000+ depending on model and any additional work
- System boiler + cylinder: £2,500–£4,000+
- Conventional boiler replacement: similar to system boilers, depending on what’s being kept/replaced
Prices vary based on the boiler chosen, complexity of the install, and whether any pipework/radiators need upgrading.
What should you ask when getting quotes?
- What boiler do they recommend and why?
- Is a power flush included or needed?
- What warranty comes with the boiler and the installation?
- Are they Gas Safe registered?
- How long will the job take?
Final thoughts
Most homes in Teesside suit a combi boiler, but if you’ve got multiple bathrooms or specific hot water needs, a system boiler might be the better choice. The key is matching the boiler to your household, not just picking the most popular option.
If you’re unsure what suits your home, it’s worth getting advice from someone who’ll actually be doing the install — they’ll spot any issues with pressure, pipework, or space that might affect the decision.
Book a free quote or get in touch if you’d like to talk through your options.