If you’re buying a home, replacing a boiler, or just trying to understand what you’ve got, central heating systems can be confusing. There are three main types: combi boilers, system boilers, and conventional (regular) boilers. Here’s what each one does, the pros and cons, and which suits different properties.
Combi Boilers
What it is: A combination boiler heats water directly from the mains when you turn on a tap or shower. No hot water storage tank needed.
How it works:
- Cold water enters the boiler from the mains
- When you open a hot tap, the boiler heats the water instantly
- Hot water flows directly to the tap at mains pressure
- The boiler also heats radiators via a closed heating circuit
Components: Just the boiler. No tanks in the loft or airing cupboard.
Typical properties: Modern builds, small flats, terraced houses, and homes where space is limited.
Pros
Space-saving: No tanks or cylinders. The boiler is usually wall-mounted in the kitchen or utility room.
Instant hot water: Turn on the tap and get hot water within seconds. No waiting for a tank to reheat.
Lower running costs: You only heat the water you use. No heat loss from stored hot water.
Good water pressure: Hot water comes out at mains pressure (assuming good mains pressure). Great for showers.
Simpler installation: Fewer components mean lower installation cost.
Cons
Limited flow rate: If you run multiple taps or showers simultaneously, water pressure drops. Not ideal for larger homes with multiple bathrooms.
Dependent on mains pressure: If your mains pressure is low (common in older Teesside estates), your hot water pressure will be poor.
No backup hot water: If the boiler breaks, you have no hot water at all.
Not suitable for power showers: Power showers need a stored hot water supply. Combi boilers can’t provide the flow rate.
System Boilers
What it is: A system boiler heats water and stores it in a hot water cylinder. It has most components built into the boiler itself, so no separate tanks are needed in the loft.
How it works:
- The boiler heats water and stores it in a hot water cylinder (usually in an airing cupboard)
- When you open a hot tap, stored hot water flows out
- The boiler refills and reheats the cylinder automatically
- The boiler also heats radiators via a closed heating circuit
Components: Boiler and hot water cylinder. No cold water tank in the loft (unlike conventional boilers).
Typical properties: Medium to large homes with 2+ bathrooms, or homes with high hot water demand.
Pros
Multiple taps at once: Stored hot water means you can run several taps or showers simultaneously without losing pressure.
Compatible with solar thermal: If you want solar panels to heat water, system boilers work well with solar thermal systems.
Good for larger homes: Handles higher hot water demand than combi boilers.
Faster hot water delivery: Hot water is already heated and ready to use.
Cons
Needs space: The hot water cylinder takes up space (usually an airing cupboard).
Heat loss: Stored hot water loses heat over time, even with insulation. This means slightly higher running costs than combis.
Limited hot water: If you empty the cylinder (e.g., multiple long showers), you need to wait for it to reheat (30-60 minutes).
More expensive to install: Cylinder and additional pipework increase installation cost.
Conventional Boilers (Regular/Traditional)
What it is: Also called a regular or traditional boiler. This is the oldest type, common in 1960s-70s Teesside estates. It uses a cold water tank in the loft, a hot water cylinder, and the boiler itself.
How it works:
- Cold water from the loft tank feeds the hot water cylinder
- The boiler heats water in the cylinder
- Hot water flows from the cylinder to taps
- A separate header tank in the loft feeds the heating circuit
Components: Boiler, hot water cylinder, cold water tank (loft), and header tank (loft).
Typical properties: Older homes built before the 1990s. Common in Teesside’s 1960s-70s estates.
Pros
Multiple taps at once: Like system boilers, stored hot water handles multiple outlets simultaneously.
Low mains pressure not a problem: Because the system relies on gravity, not mains pressure, it works fine in areas with poor mains pressure.
Compatible with older radiator systems: If you have an old heating system, conventional boilers work well without requiring upgrades.
Good for very large homes: If you have 3+ bathrooms and high hot water demand, a conventional boiler with a large cylinder works well.
Cons
Space-hungry: You need space for the boiler, cylinder, and two loft tanks.
Lower water pressure: Gravity-fed systems have lower pressure than mains-fed systems. Showers might need a pump.
Longer hot water recovery: After emptying the cylinder, it takes longer to reheat than a system boiler.
Complex installation: More components mean higher installation cost and more potential failure points.
Outdated: Few new installs use conventional boilers. They’re being phased out in favour of combi and system boilers.
Which System Suits Your Property?
Here’s a rough guide based on Teesside property types:
Small Terraced House or Flat
Best choice: Combi boiler.
Why: Limited space, usually 1 bathroom, low simultaneous hot water demand. A combi saves space and provides instant hot water.
Check: Make sure your mains pressure is decent. If it’s low, you might need a system boiler with a pump.
Medium Semi-Detached or Mid-Terrace (2-3 bedrooms, 1 bathroom)
Best choice: Combi boiler (if mains pressure is good) or system boiler (if you want stronger showers or have low mains pressure).
Why: A combi works fine for most families, but if you frequently have two people showering at the same time, a system boiler handles it better.
Larger Detached or 4+ Bedrooms (2+ bathrooms)
Best choice: System boiler.
Why: Multiple bathrooms and high hot water demand. A system boiler provides enough hot water for simultaneous use without pressure drops.
Alternative: A high-output combi boiler can work, but check the flow rate carefully. You’ll need at least 15-18 litres per minute for two showers running simultaneously.
Older Property with Existing Conventional System
Best choice: Upgrade to a system boiler (or combi if space is a priority).
Why: Conventional boilers are outdated and less efficient. If your boiler needs replacing, it’s worth upgrading.
Note: Many 1960s-70s Teesside estates still have conventional systems. Upgrading to a system boiler often means removing the loft tanks (freeing up loft space) and installing a hot water cylinder.
Upgrade Paths
If you’re replacing an old boiler, here are common upgrade routes:
Conventional → Combi: Removes all tanks and cylinders, freeing up space. Requires good mains pressure. Installation cost: £1,800-£2,800.
Conventional → System: Removes loft tanks but keeps the cylinder (or installs a new one). Better for larger homes. Installation cost: £2,200-£3,500.
System → Combi: Removes the cylinder to save space. Only do this if your hot water demand is low. Installation cost: £1,800-£2,500.
Combi → System: Adds a hot water cylinder to handle higher demand. Useful if you’re adding bathrooms. Installation cost: £2,500-£4,000.
Teesside-Specific Considerations
1960s-70s estates: Many still have conventional boilers with loft tanks. These are prime candidates for upgrading to system boilers. You’ll gain loft space, improve efficiency, and get better shower pressure (with a pump).
Victorian terraces: Often small with 1 bathroom. Combi boilers are ideal here if mains pressure is decent. Older properties might have low mains pressure, so check before committing.
Modern builds: Almost all have combi boilers. If you’re buying new, a combi is standard and works fine.
Low mains pressure areas: Some parts of Teesside have low mains pressure (check by running a tap full blast and timing how long it takes to fill a 10-litre bucket). If it’s under 10 litres per minute, a combi won’t perform well. Choose a system boiler with a pump instead.
Costs Overview
Rough costs for Teesside in 2026:
Combi boiler replacement (like-for-like): £1,800-£2,500
System boiler replacement (with existing cylinder): £2,200-£3,000
System boiler installation (adding new cylinder): £2,800-£4,000
Conventional boiler replacement (like-for-like, rare now): £2,500-£3,500
Prices vary based on boiler brand, property access, and any additional work (new pipework, radiator upgrades, etc.).
The Bottom Line
Combi boilers are great for smaller homes with low hot water demand. Space-saving and efficient, but not ideal for multiple bathrooms.
System boilers suit medium to large homes with higher hot water demand. They handle multiple taps well and work with solar thermal.
Conventional boilers are outdated. If you have one, consider upgrading when it needs replacing.
If you’re unsure which system suits your Teesside home, we’re happy to advise. We’ll check your mains pressure, assess your hot water needs, and recommend the best system for your property.
Get a free quote or contact us to discuss your central heating system.
Related services: Central Heating | Boiler Installation | Radiators