Combi Boiler vs System Boiler
Make an informed decision about Combi Boiler vs System Boiler for your North London home.
Combi Boiler
A combination boiler provides both central heating and hot water on demand, without needing a separate hot water cylinder or cold water storage tank.
✓ Advantages
- ✓Compact - no cylinder or tank needed
- ✓Instant hot water on demand
- ✓More energy efficient (no heat loss from stored water)
- ✓Lower installation costs
- ✓Ideal for smaller properties
- ✓Easier to install and maintain
✗ Disadvantages
- ✗Water pressure drops if multiple taps used
- ✗Not suitable for large households (4+ bathrooms)
- ✗Can't power multiple showers simultaneously
- ✗No backup hot water if boiler fails
- ✗May struggle with low incoming water pressure
Best for: Flats and apartments, 1-3 bedroom houses, Properties with 1-2 bathrooms, Homes without loft space, Energy-conscious homeowners
Price range: £1,800 - £3,500 installed
System Boiler
A system boiler works with a hot water cylinder (usually in an airing cupboard) to store hot water, but doesn't require a cold water tank in the loft.
✓ Advantages
- ✓Can supply multiple bathrooms simultaneously
- ✓Consistent water pressure throughout
- ✓Compatible with solar thermal systems
- ✓Hot water stored means backup supply
- ✓Better for high hot water demand
- ✓Works well with underfloor heating
✗ Disadvantages
- ✗Requires space for hot water cylinder
- ✗Higher installation costs
- ✗Heat loss from cylinder (even if insulated)
- ✗Wait time for cylinder to reheat
- ✗More complex installation
Best for: 4+ bedroom houses, Properties with 3+ bathrooms, Large families, Homes with multiple showers, Properties with solar panels
Price range: £2,500 - £4,500 installed
Side-by-Side Comparison
| Feature | Combi Boiler | System Boiler |
|---|---|---|
| Space Required | Minimal (wall-mounted only) | Cylinder cupboard needed |
| Hot Water Delivery | Instant, on-demand | Stored, may need reheating |
| Multi-Bathroom Use | Pressure drops | Consistent pressure |
| Installation Cost | £1,800 - £3,500 | £2,500 - £4,500 |
| Running Costs | Lower (on-demand) | Slightly higher |
| Solar Compatibility | Limited | Excellent |
| Large Family Suitability | Up to 3 bed | 4+ bed |
| Maintenance | Simpler, fewer parts | Cylinder + boiler |
Our Expert Verdict
For most North London properties (flats and 2-3 bed houses), a combi boiler is the best choice. System boilers make sense for larger properties with high hot water demand or solar thermal systems.
Choose Combi Boiler if:
- →You have a flat or small house (1-3 bedrooms)
- →Space is at a premium
- →You only have 1-2 bathrooms
- →You want lower installation costs
- →Energy efficiency is a priority
Choose System Boiler if:
- →You have 4+ bedrooms
- →Multiple people shower simultaneously
- →You have or plan to install solar thermal
- →Consistent water pressure is essential
- →You have space for a cylinder cupboard
Frequently Asked Questions
Can I switch from a system boiler to a combi?▼
Yes, it's a common conversion in London. We remove the cylinder and cold water tank (if present), freeing up valuable space. Typical cost: £2,500-£4,000 including the new combi.
Will a combi cope with my power shower?▼
Combis can't power pumped power showers (they're designed for gravity systems). However, modern combis deliver 10-15 litres/minute which feels powerful. We'll assess your water pressure to recommend the best solution.
Which boiler type is better for the environment?▼
Combis are generally more efficient as they don't store hot water (no standby heat loss). However, if you have solar thermal panels, a system boiler with a thermal store is greener overall.
How long do combi and system boilers last?▼
Both typically last 10-15 years with annual servicing. Premium brands (Worcester, Vaillant) often last longer. System boilers may have additional cylinder maintenance requirements.
Related Comparisons
Need Expert Advice?
Our experienced team can help you decide which option is best for your home. Get personalized advice and a free, no-obligation quote.