System Boiler Guide
Boiler that works with a separate hot water cylinder, ideal for homes with multiple bathrooms.
UK Market Share
25%
Avg Efficiency
91%
Price Range
£700 - £2,100
Typical Warranty
10yr
What Does a System Boiler Look Like?
Typical system boiler installation in a UK home
How System Boilers Work
Overview
System boilers work with a sealed hot water cylinder, storing hot water for use throughout the home. Unlike regular boilers, they have most components built into the boiler itself, making installation neater and simpler. They are ideal for homes with higher hot water demands.
The Process:
The system boiler heats water which is stored in a hot water cylinder (typically 150-300 litres). When you turn on a hot tap, stored hot water flows out and is automatically topped up and reheated. For central heating, the boiler heats water which circulates through radiators. The system includes a built-in pump and expansion vessel.
System Diagram
Complete system layout showing water flow and heating distribution
System Boiler Pros and Cons
Advantages
Multiple taps simultaneously
Can supply hot water to multiple outlets at the same time without pressure drop.
Compatible with solar panels
Works well with solar thermal systems for added efficiency.
Constant hot water supply
Cylinder stores hot water, ensuring supply during high demand periods.
Good for larger homes
Ideal for properties with 3+ bedrooms and multiple bathrooms.
More space than Regular
Doesn't require a cold water tank in the loft, saving some space.
Reliable performance
Proven technology with consistent hot water delivery.
How System Boilers compare to other types
Disadvantages
Requires cylinder space
Need room for hot water cylinder, usually in airing cupboard.
Can run out of hot water
Once cylinder empties, need to wait for it to reheat.
Heat loss from cylinder
Stored hot water loses heat over time, slightly less efficient.
More complex installation
Costs more to install than combi boiler due to additional components.
Initial recovery time
Takes time to initially heat up full cylinder after installation.
Is a System Boiler Right for Your Home?
Suitability Overview
✓ Best suited for:
Medium to large homes (3-5 bedrooms) with 2+ bathrooms, properties with multiple family members, homes requiring simultaneous hot water to several outlets, properties suitable for solar thermal panels
✗ Not suitable for:
Small flats or homes with limited space for a cylinder, properties with single bathroom and low hot water usage, homes where space is at an absolute premium
Ideal property types
Detailed Suitability by Property Type
| Property | Beds | Baths | Score | Recommendation |
|---|---|---|---|---|
| Detached House | 4 | 2 | 10/10 | Excellent Perfect for detached house with multiple bathrooms |
| Detached House | 5 | 3 | 10/10 | Excellent Best choice for large family home with high hot water demand |
| Semi-Detached | 3 | 2 | 9/10 | Excellent Ideal for semi-detached with 2 bathrooms |
| Bungalow | 2 | 1 | 7/10 | Good Suitable for bungalow, especially if future-proofing |
| Terraced House | 2 | 1 | 6/10 | Fair Works but combi usually more suitable for this size |
| Flat | 1 | 1 | 4/10 | Poor Overkill for small flat, wastes space |
Space Requirements & Installation
Components You'll Need Space For
Boiler unit
RequiredSize: 700mm H x 400mm W x 300mm D
Location: Kitchen or utility room wall
Hot water cylinder
RequiredSize: 1500mm H x 450mm diameter
Location: Airing cupboard or utility
Typical Installation
Professional installation takes 1-2 days depending on your existing system
Annual Running Costs
What You'll Pay Each Year
Small (1-2 bed)
£1030
per year (estimated)
Medium (3-4 bed)
£1505
per year (estimated)
Large (4+ bed)
£1980
per year (estimated)
💡 Tip: Running costs vary based on your heating usage, insulation quality, and local energy prices. These figures are UK averages based on typical usage patterns.
Popular System Boiler Models
| Manufacturer | Model | Output | Efficiency | Price | Warranty |
|---|---|---|---|---|---|
| Worcester Bosch | Greenstar 4000 System | 30 kW | 94%A-rated | £1,300 | 10 years |
| Vaillant | ecoTEC Pro System | 30 kW | 94%A-rated | £1,450 | 10 years |
| Baxi | EcoBlue Advance System | 32 kW | 93% | £1,100 | 7 years |
| Ideal | Vogue Max System | 32 kW | 94%A-rated | £1,200 | 10 years |
Prices shown are for the boiler unit only. Installation costs typically range from £800 - £2,000. Get free quotes from local installers for accurate pricing.
Frequently Asked Questions
What's the difference between a system boiler and a combi boiler?
A system boiler stores hot water in a cylinder, allowing multiple taps to run simultaneously. A combi heats water on demand with no storage. System boilers are better for homes with high hot water demand.
How much space do I need for a system boiler?
You'll need wall space for the boiler unit (similar to a combi) plus space for a hot water cylinder, typically in an airing cupboard. The cylinder is usually 450mm diameter and 1500mm high.
Can I run out of hot water with a system boiler?
Yes, if you use more hot water than the cylinder can store. However, modern cylinders are well-insulated and the boiler reheats quickly. Typical 200L cylinders provide enough for 2-3 baths.
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