How Does A Combi Boiler Work? - Climastar
How Does A Combi Boiler Work

How Does A Combi Boiler Work?

Understanding how a combi boiler, specifically an electric one, works can save you time, reduce energy costs, and contribute to a greener environment. This guide explores the ins and outs of electric combi boilers, how they differ from their gas and traditional counterparts, and why they may be the ideal choice for your home. So, how does a combi boiler work?

What is a Combi Boiler & How Does A Combi Boiler Work?

Combination boilers, or combi boilers, are multipurpose devices that provide central heating and instant hot water. Unlike conventional heating systems, they don’t require separate water tanks, making them perfect for homes with limited space.

The Focus on Electric Combi Boilers

In this article, we’re honing in on electric combi boilers, a variety that has been making waves for its efficiency and environmental friendliness.

Who Needs to Know How a Combi Boiler Works?

The information in this article is for homeowners interested in making an informed choice, technicians looking for a refresher, or anyone keen to reduce their carbon footprint.

What Makes Combi Boilers Different

Traditional Boilers vs. Combi Boilers


While traditional boilers require a separate cylinder for storing hot water and sometimes even a cold-water tank in the loft, combi boilers consolidate all these functions into one unit. This space-saving feature is particularly beneficial for small apartments and homes.


Combi boilers heat water directly from the mains when you turn on a tap, meaning you don’t need to store water in a cylinder. This on-demand approach contributes to higher efficiency and reduced energy costs.


Combi boilers, due to their smaller size and fewer components, are usually quicker and less complicated to install than traditional systems.

Gas vs. Electric Combi Boilers


Gas boilers are often cheaper to run but come with installation complications such as gas lines and exhaust venting. Electric combi boilers offer a simpler installation process, often making them more cost-effective upfront.

Environmental Impact

When powered by renewable energy sources, electric combi boilers become a zero-emissions solution for heating your home.

Safety Features

Electric combi boilers come with multiple safety features like overheat cut-offs and pressure relief valves, making them generally safer to operate than gas boilers.

Core Components of an Electric Combi Boiler

The Heating Element

This is essentially the heart of the electric combi boiler. A resistive electrical element heats the water. When electrical current flows through the element, it heats up, transferring this heat to the water circulating around it.


The thermostat is the ‘brain’ of the operation. It monitors the room temperature and signals the boiler to start or stop heating water. Modern thermostats allow you to programme temperature schedules, optimising energy use.

Circulator Pump

This is the ‘muscle’ that pushes hot water from the boiler into the radiators and plumbing throughout the house. It ensures an even distribution of heat.

Expansion Vessel

This component helps manage pressure. When water heats up, it expands. The expansion vessel compensates for this, maintaining system pressure and preventing potential ruptures.

Pressure Relief Valve

The pressure relief valve serves as a safety mechanism. If the pressure becomes too high, this valve releases it, preventing potential accidents.

Control Panel

This is the user interface where you can set your preferred temperature, timing, and sometimes even access diagnostic information.

How Does an Electric Combi Boiler Work?

The Basic Working Principle

When you turn on the heating or request hot water, the electric elements heat up due to electrical resistance. The thermostat controls this process, activating the elements as needed.

The Heating Process

Activation via Thermostat

Once the thermostat detects a temperature below the set level, it signals the boiler to activate the heating elements.

Heating the Water

As electrical current passes through the heating elements, the water in contact gets heated.


The circulator pump then moves this hot water to radiators and taps, replacing it with cold water that then gets heated by the elements.

The Domestic Hot Water Supply

On-Demand Heating

When you turn on a hot water tap, the boiler senses the flow and starts heating water instantly. There’s no waiting time, and you only heat what you use.

Flow Rate Considerations

Different boilers come with different flow rates, affecting how much hot water can be delivered at once. Before purchase, ensure the model can meet your household’s needs.

Advantages of Using an Electric Combi Boiler

Energy Efficiency

Electric combi boilers have almost 100% energy efficiency levels since all the electricity used goes into heating the water or home.

Lower Carbon Footprint

If your electricity comes from renewable sources, your boiler operation can be carbon-neutral, which is excellent for the environment. Further to this, they can also integrate with our electric radiators.

Safety Features

With no risk of gas leaks or carbon monoxide poisoning, electric combi boilers are generally safer to operate.

Ease of Installation and Maintenance

Because they’re less complicated than their gas counterparts and don’t require a flue or gas supply, electric combi boilers are simpler and generally cheaper to install and maintain.

Common Concerns and Solutions

Initial Installation Costs

Though electric combi boilers might have a higher initial purchase price, their lower maintenance and operation costs often make them more economical in the long run.

Power Outages

During a power outage, an electric boiler will stop functioning. However, these instances are typically rare and can be mitigated with a backup generator.

Water Pressure Issues

Solutions for Low Water Pressure

If your home has low water pressure, a booster pump can help.

Precautions for High Water Pressure

For homes with high water pressure, pressure-reducing valves and regular servicing can help maintain your system.

Maintenance Tips for Your Electric Combi Boiler

Regular Inspection

Conduct monthly checks for any signs of wear or malfunction. The sooner you identify a problem, the easier it is to fix.

Cleaning the Boiler

A simple dusting or vacuuming around the boiler can help keep it running efficiently.


If you live in a hard water area, descaling is essential. Either use a chemical descaler or hire a professional.

Professional Servicing

An annual service by a qualified technician can help prolong your boiler’s lifespan and ensure it runs efficiently.

Climastar UK’s Electric Combi Boiler Offerings


Climastar UK offers a range of electric boilers, including combi boilers, designed for maximum efficiency and user-friendliness. With digital control panels, multiple safety features, and high energy ratings, our boilers are built for the modern home.


When you opt for a Climastar UK electric combi boiler, you benefit from ease of installation, low maintenance, and the peace of mind that comes with a safer, greener choice.

Why Electric Combi Boilers are the Future

In an age of increasing environmental consciousness and the drive towards renewable energy, electric combi boilers offer a future-ready option for home heating and hot water supply.

Final Thoughts on How Electric Combi Boilers Work

Understanding your home’s electric heating system is not just empowering; it’s responsible homeownership. Electric combi boilers offer an efficient, environmentally friendly and safe solution for your home’s heating and hot water needs. With their simple operation, high efficiency, and green credentials, they are becoming the go-to choice for new installations and system upgrades.

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