Back Boiler vs Combination Boiler
Compare these two popular boiler types to find which suits your home best
Back Boiler
Older style boiler fitted behind a fireplace, now being phased out.
Combination Boiler
All-in-one boiler providing heating and hot water on demand without the need for separate tanks or cylinders.
Key Statistics
Advantages Comparison
Back Boiler Advantages
Combination Boiler Advantages
Space-saving design
No need for separate hot water cylinder or cold water tank, freeing up valuable cupboard space.
Instant hot water
Hot water is heated on demand, so you never run out and don't waste energy heating a tank.
Lower installation costs
Simpler installation with fewer components means lower upfront costs.
Energy efficient
Only heats water when needed, reducing energy waste.
Good water pressure
Water comes directly from the mains, providing strong pressure.
Cheaper to run
No heat loss from storing hot water, making running costs lower.
Disadvantages Comparison
Back Boiler Disadvantages
Very inefficient
Efficiency typically only 60-70%, much lower than modern boilers.
Expensive to replace
Removal and conversion to new system costs £2,000-£3,500.
No longer manufactured
Can't buy new back boilers, making repairs difficult.
Difficult to access for repairs
Located behind fireplace, making servicing challenging.
High running costs
Poor efficiency means much higher energy bills.
Combination Boiler Disadvantages
Limited hot water flow rate
Water flow reduces if multiple taps are used simultaneously.
Not ideal for multiple bathrooms
Struggles to supply enough hot water when demand is high.
Performance depends on mains pressure
Poor water pressure will result in weak flow from taps.
No backup hot water
If boiler breaks down, you have no heating or hot water.
Temperature can fluctuate
Water temperature may vary when multiple outlets are used.
Space Requirements Comparison
Back Boiler
Combination Boiler
Boiler unit
Required700mm H x 400mm W x 300mm D
Annual Running Costs Comparison
| Property Size | Back Boiler | Combination Boiler | Difference |
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Which Should You Choose?
Choose Back Boiler If...
✓ Best suited for:
No longer recommended - should be replaced with a modern alternative
✗ Not suitable for:
All properties - back boilers are obsolete technology and should be replaced
Choose Combination Boiler If...
✓ Best suited for:
Small to medium homes (1-3 bedrooms) with 1-2 bathrooms, flats, properties with limited space, homes with good mains water pressure
✗ Not suitable for:
Large homes with multiple bathrooms being used simultaneously, properties with poor mains water pressure, homes with very high hot water demand
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