Central Heating System

What Is a Central Heating System

A central heating system warms your home using a single heat source, usually a boiler or a heat pump.

The heat source raises the temperature of water, which then flows through pipes and radiators to keep each room warm.

How a heating system warms your home

Most systems in the UK use hot water.

The boiler or heat pump heats water, pumps it around the home and then returns it to be reheated.

Your thermostat tells the system when to switch on or off to keep your home at a steady temperature.

The main parts homeowners need to know

• A boiler or heat pump

• Radiators or underfloor heating

• A pump that moves hot water around the home

• Controls such as a thermostat and timer.
  (Some systems also have a hot water cylinder. Others produce hot water instantly)

If you ever notice cold patches on a radiator, our guide on how to fix radiator sludge can help you understand what might be causing it.

Combi Boiler Central Heating Systems

A combi boiler is the most common choice in UK homes.

It provides heating and hot water directly from the boiler without the need for a hot water cylinder or storage tanks.

How a combi boiler works

A combi heats water instantly whenever a hot tap is turned on.

It switches between heating your radiators and heating your hot water based on demand.

Who a combi boiler is best for

• Homes with one bathroom

• Small or medium sized homes

• Properties with limited storage space

• Households that want simple, fast hot water

Pros of combi boilers

• Compact

• No hot water cylinder needed

• Heats water only when required

• Good energy efficiency in small homes

Cons of combi boilers

• Can struggle with high hot water demand

• Not ideal for homes with two or more bathrooms

• Relies on good mains water pressure

Typical UK installation cost

A new combi boiler usually costs between £2,000 and £3,000 including installation.

Prices vary depending on brand, model and any additional work required.

Real example

A one bathroom terraced home with limited space will often choose a combi because it offers fast hot water without needing a cylinder.

System Boiler Central Heating Systems

A system boiler heats your home and stores hot water in a cylinder.

This makes it suitable for homes with higher hot water demand.

How a system boiler works

The boiler heats water for your radiators and also heats stored water in a cylinder.

The cylinder keeps a supply of hot water ready for use.

Who a system boiler suits

• Homes with two or more bathrooms

• Households that use hot water at the same time

• Homes with space for a cylinder

Pros of system boilers

• Strong hot water performance

• Good for larger families

• Can run multiple taps at once

• No need for loft tanks

Cons of system boilers

• Requires a hot water cylinder

• Takes up more space

• Uses more energy than a combi if hot water is stored and not used

Typical UK installation cost

A system boiler usually costs between £2,500 and £3,500 including installation, although prices are higher if a new hot water cylinder is needed.

Real example

A four bedroom home with two bathrooms and regular morning showers will often choose a system boiler because it can supply steady hot water to several taps.

Heat Only Regular Boiler Systems

A heat only boiler, sometimes called a regular or traditional boiler, is part of an older style system with a hot water cylinder and additional storage tanks.

How a heat only system works

The boiler heats water and sends it to radiators and a hot water cylinder.

Cold water tanks in the loft feed the system.

When this type is still useful

Heat only boilers are often best for homes that already have this layout.

Converting to a different system can be costly, so many homeowners keep the same style and upgrade the boiler.

Pros of heat only boilers

• Works well in older properties

• Good at handling high hot water demand

• Often compatible with existing pipework

Cons of heat only boilers

• Needs loft tanks

• Takes up the most space

• Slower to install

• Less efficient than modern combi and system boilers

Typical UK installation cost

A heat only boiler usually costs between £2,300 and £3,300 including installation. Costs vary based on the condition of the existing system.

Real example

A large older property with a hot water cylinder and tanks already installed will often replace the existing heat only boiler rather than changing the entire layout.

Air Source Heat Pump Heating Systems

Air source heat pumps are an increasingly popular option for UK homes.

They use electricity to draw heat from the outside air and transfer it into your home.

How an air source heat pump works

A heat pump absorbs heat from the air outside and compresses it to raise the temperature.

The heat is then used to warm your radiators or underfloor heating.

When a heat pump is a good option

• Homes with good insulation

• Homes aiming to reduce carbon emissions

• Properties with space outside for the heat pump

• Homes where radiators can be sized correctly for lower flow temperatures

Pros of air source heat pumps

• Very efficient

• Lower carbon emissions

• Works well with underfloor heating

• Provides steady, comfortable warmth

Cons of air source heat pumps

• Higher upfront cost

• Works best with good insulation

• Some homes need radiator upgrades

• Requires an outdoor unit

Typical UK installation cost

Most air source heat pumps cost between £7,000 and £14,000 depending on the home.

Larger homes or homes needing radiator upgrades can be higher.

If you want to check financial support for low carbon heating, our overview of the Boiler Upgrade Scheme for heat pumps gives a simple breakdown of how the scheme works.

Real example

A well insulated three bedroom semi detached home often finds that a heat pump provides steady heating and reduces running costs compared to older boilers.

Comparison Table: Boiler Types and Heat Pumps

How to Choose the Right Central Heating System for Your Home

Choosing the right heating system depends on several practical factors.

Number of bathrooms

Homes with more than one bathroom usually need a system boiler or heat only boiler for stronger hot water performance.

Space for a hot water cylinder

If you have space for a cylinder, a system boiler or heat pump may be suitable.

If you do not, a combi boiler is often the best choice.

Budget and running costs

Combi boilers are usually the most cost effective to install.

System boilers cost more but provide better hot water performance.

Heat pumps have higher upfront costs but can reduce running costs in well insulated homes.

Water pressure considerations

Combi boilers rely on strong mains water pressure.

If your water pressure is low, a system or heat only boiler may be more reliable.

Insulation and future energy plans

Homes with strong insulation are well suited to heat pumps, which run best at lower temperatures.

When to Replace Your Heating System

You may need to replace your heating system if:

• Your boiler is over 12 to 15 years old

• You experience regular breakdowns

• Your heating bills have increased

• Hot water flow is weak or unreliable

• Repairs are becoming frequent and costly

If you have noticed small leaks around a radiator valve, our leaking radiator valve guide explains the common causes in simple terms.

Safety reminders

Only a Gas Safe registered engineer can work on gas boilers.

Heat pumps should be installed by trained and qualified professionals.

If you are deciding whether to repair or replace your boiler, our boiler repair guidance can help you understand the factors an engineer will check.

Final Thoughts on Central Heating Systems

The best central heating system for your home depends on how much hot water you use, how much space you have and the type of property you live in.

Combi boilers suit smaller homes, system boilers suit homes with higher hot water demand and heat pumps are ideal for well insulated homes looking for lower carbon heating.

iHeat Help

iHeat installs new boilers and air source heat pumps, including popular models from Worcester Bosch, Vaillant and Alpha.

Our team can guide you through the options and help you choose a system that suits your home, budget and heating needs.

Free online quotes and fast installation are available across the UK.

Get a quote