Combi vs Conventional Boilers for Home Heating

When it comes to heating your home efficiently, choosing the right boiler is crucial.

Two popular options in the market are combi boilers and conventional boilers. Each has its own set of advantages and drawbacks, making the decision-making process challenging for homeowners. In this article, we’ll explore the differences between combi and conventional boilers to help you determine which one is better suited for your needs.

Combi Boilers

Combi, or combination boilers, are compact units that provide both hot water for taps and central heating. They don’t require a separate hot water cylinder or cold-water tank, making them ideal for homes with limited space.

Combi boilers heat water on demand, meaning there’s no need to wait for a cylinder to refill, resulting in instant hot water whenever you need it. Since they heat water directly from the mains, they are more energy-efficient, reducing energy bills and carbon emissions.

Pros of Combi Boilers

Space-saving: Combi boilers are compact and do not require additional tanks or cylinders, making them suitable for small properties or homes with limited space.

Energy-efficient: By heating water on demand, combi boilers eliminate the need for storing hot water, reducing energy wastage and lowering utility bills.

Instant hot water: With no waiting time for water to heat up, combi boilers provide hot water on demand, ensuring convenience and comfort.

Cons of Combi Boilers

Limited hot water supply: Since combi boilers heat water on demand, the flow rate may be insufficient for simultaneous use of multiple taps or appliances.

Unsuitable for larger properties: Homes with multiple bathrooms or high hot water demand may find combi boilers inadequate due to their limited flow rate.

Conventional Boilers

Conventional, or heat-only boilers, consist of a boiler unit, hot water cylinder, and cold-water tank. They store hot water in a cylinder, which can be heated either by the boiler or an immersion heater. Conventional boilers are suitable for larger properties with multiple bathrooms, as they can provide a steady supply of hot water to several outlets simultaneously.

Pros of Conventional Boilers

High hot water output: Conventional boilers store hot water in a cylinder, ensuring a continuous supply of hot water to multiple taps and appliances.

Suitable for larger properties: Homes with high hot water demand or multiple bathrooms benefit from the ample hot water supply provided by conventional boilers.

Compatible with existing systems: Conventional boilers are often compatible with existing heating systems, making them a convenient choice for replacement installations.

Cons of Conventional Boilers

Space requirements: Conventional boilers require separate hot water cylinders and cold-water tanks, occupying more space compared to combi boilers.

Heat loss: Hot water stored in cylinders can experience heat loss over time, reducing energy efficiency and potentially increasing energy bills.

Slower hot water delivery: Unlike combi boilers, conventional boilers may require time to heat up water stored in the cylinder, resulting in delays in hot water delivery.


Choosing between combi and conventional boilers depends on various factors such as property size, hot water demand, and space availability.

Combi boilers offer space-saving benefits and energy efficiency, making them ideal for small to medium-sized properties with low to moderate hot water demand.

On the other hand, conventional boilers provide ample hot water for larger properties with multiple bathrooms or high hot water usage.

Consider your specific requirements and consult with a qualified heating engineer to determine which boiler type is better suited for your needs.