With over 15 years of experience installing and maintaining combination boilers, NOVATEC engineers provide expert insights into why combi boilers are the preferred choice for 70% of UK households.
A combi boiler (combination boiler) is a compact heating system that delivers central heating and instant hot water directly from mains supply. Unlike conventional boilers with cylinders and tanks, combi boilers heat water on-demand via a high-efficiency heat exchanger.
Key advantage: hot water is produced instantly whenever a tap or shower is opened, eliminating storage losses entirely.
Replaces boiler + cylinder + loft/airing cupboard tanks with a single wall-mounted unit.
Ideal for apartments, terraced houses, and modern builds.
NOVATEC Tip: Freed space can be repurposed for storage or a mini office.
Efficiency: 90–94% (A-rated), almost all fuel converts to heat.
Savings vs conventional systems:
| Factor | Conventional | Combi Boiler | Annual Savings |
|---|---|---|---|
| Heat Loss | 10-15% | Zero storage loss | £80-£150 |
| Combustion Efficiency | 70-80% | 90-94% | £120-£200 |
| Heating Control | Limited | Precise modulation + smart controls | £60-£100 |
| Pipework Loss | Extensive | Minimal | £30-£50 |
Average savings: 25–35% on energy bills (£300–£450/year).
Continuous supply without waiting for cylinders to reheat.
Typical flow rates:
| Model | Flow Rate | Suitable For |
|---|---|---|
| 24–28 kW | 10–12 L/min | 1 bathroom |
| 30–35 kW | 12–15 L/min | 2 bathrooms |
| 35+ kW | 15+ L/min | Larger properties |
Note: Flow may reduce with multiple simultaneous uses.
Mains-fed pressure: 1.5–3 bar (vs 0.1–0.5 bar gravity-fed)
Eliminates sediment, bacteria, and metallic taste from tanks.
Safety Tip: No stored lukewarm water reduces Legionella risk.
Installation: 1–2 days vs 2–3 days for conventional systems.
Fewer components → fewer failure points.
Annual service: £80–£100 (vs £120–£150 for conventional systems).
Reduced gas consumption: 25–35% lower → 500–700 kg CO2 saved annually.
Condensing technology recovers exhaust heat.
Hydrogen-ready models future-proof for net-zero energy networks.
Compatible with Nest, Hive, Tado, Alexa, Google Home.
Outdoor sensors, energy analytics, and remote diagnostics.
Optimize comfort and reduce costs automatically.
Consider alternatives if:
Large properties (4+ bedrooms, 3+ bathrooms)
Low mains pressure (<1.5 bar)
Existing solar hot water systems
Restricted rural flow rates (<12 L/min)
NOVATEC approach: Site surveys ensure correct system selection.
| Criterion | Combi Boiler | Conventional System | NOVATEC Recommendation |
|---|---|---|---|
| Space Required | 0.5-0.7 m² (wall-mounted) | 3-5 m² (boiler, cylinder, tanks) | Combi for space-constrained properties |
| Installation Cost | ₴90,000-₴175,000 | ₴125,000-₴225,000 | Combi offers better value for typical homes |
| Energy Efficiency | 90-94% (A-rated) | 88-91% (with modern cylinder) | Combi marginally more efficient |
| Hot Water Wait Time | 5-15 seconds | Instant (stored), 60+ min (reheating) | Combi better for spontaneous use |
| Multiple Outlets | Limited by flow rate | Excellent (stored volume) | Conventional for high simultaneous demand |
| Water Pressure | Mains pressure (1.5-3 bar) | Gravity-fed (0.1-0.5 bar) unless pumped | Combi provides superior pressure |
| Maintenance | Annual service ₴4,000-₴5,000 | Annual service ₴6,000-₴7,500 | Combi lower long-term maintenance |
| Lifespan | 10-15 years (with service) | Boiler 10-15 years, cylinder 15-25 years | Similar overall longevity |
Key engineering criteria:
Output (kW): 24–28 kW for single bathroom, 28–32 kW for 1–2 bathrooms, 35+ kW for larger homes.
Modulation: Wide range (up to 1:10) prevents inefficient cycling.
Flow Temperature Control: Weather/load compensation ensures condensing efficiency.
Build & Warranty: Stainless steel heat exchangers, 7–10 year warranty on premium models.
NOVATEC Tip: Avoid oversizing—reduces efficiency.
Process (1–2 days):
System draining & removal
Pipework modification
Boiler mounting
Flue installation
Gas, water, heating, electrical connections
Filling, pressurization, venting
Commissioning & handover
Maintenance Tips:
Annual Gas Safe service
Monthly pressure checks (1–1.5 bar)
Quarterly filter cleaning in hard water areas
Frost protection in winter
Data: Serviced boilers maintain 92%+ efficiency at 10 years; unserviced drop to 75–80%.
| Cost Component | Combi Boiler (10 Years) | Conventional System (10 Years) | Combi Advantage |
|---|---|---|---|
| Initial Installation | ₴125,000 | ₴160,000 | ₴35,000 saving |
| Annual Service ×10 | ₴45,000 | ₴67,500 | ₴22,500 saving |
| Energy Costs ×10 | ₴600,000 | ₴775,000 | ₴175,000 saving |
| Repairs (Average) | ₴20,000 | ₴32,500 | ₴12,500 saving |
| Total 10-Year Cost | ₴790,000 | ₴1,034,000 | ₴244,000 saving (≈24% reduction) |
Pressure loss: Re-pressurize, inspect expansion vessel.
No hot water: Plate heat exchanger or diverter valve issues.
Kettling noises: Limescale on heat exchanger; clean or replace.
Frozen condensate pipe: Thaw safely, insulate to prevent recurrence.
Safety Notice: DIY gas work is illegal and dangerous. Always use Gas Safe engineers.
Q: How does a combi boiler work?
A: Dual heat exchangers—primary for central heating, secondary for instant hot water. Flow sensor diverts heat instantly when tap opens.
Q: Suitable for large homes?
A: Depends on simultaneous hot water use. Staggered usage works well with properly sized combi.
Q: Boiler lifespan?
A: 10–15 years with annual professional servicing.
Q: Efficiency vs conventional?
A: 2–6% higher due to elimination of storage losses; real-world savings 25–35%.
Q: Can I use with underfloor heating?
A: Yes, ideal due to lower flow temperatures and sustained condensing efficiency.
Do you have any questions about our products? Need advice? We are always ready to help you make the right choice. Leave a request, and our specialists will contact you as soon as possible to provide all the necessary information.
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