Central heating systems

What is central heating?

Central heating generates heat at one point, then distributes it through the rest of the rooms in a home. It normally heats up water too.

In colder climates, central heating systems are a key part of making our homes liveable, especially over winter. And thankfully here in the UK, where the weather is often miserable, most of us are lucky enough to have a central heating system.

How does central heating work?

Central heating systems can work using water, air or electricity, or a combination. In the UK, most of us have some type of hot water central heating system, also called a ‘wet’ system.

What types of heating systems are there?

Central heating systems typically fall into one of a few categories:

Wet central heating systems

Wet heating systems typically provide both heat and hot water.

In a wet system, the boiler burns fuel to heat up a copper pipe containing water. This hot water is then pumped into radiators around your home.

Alternatively, it can run through pipes under the floor to warm the space from below.

Wet heating systems use different types of boilers and can run on different fuels, including gas and oil.

Low-carbon methods for wet systems include ground source and air source heat pumps. Here, a very efficient pump extracts heat from the air or pipes running through the ground, and transfers it round your home.

Electric central heating systems

Types of electric heating system include electric boilers. These use electricity to heat water using a heating element, in much the same way as a kettle heats up the water for your afternoon brew.

There are also electric radiators. They work by using electricity to power a heating element that heats the air in a room. These can be expensive to run so are often used alongside a central heating system.

Electric storage heaters contain a heating element, typically made from materials like ceramic and clay, that are good at storing heat. They typically run overnight, when electricity is cheaper, to collect and store energy. They then release the stored heat throughout the day.

Infrared heating panels transfer heat into a room through conduction, convection or radiation.

As well as panels, infrared heating can come in the form of underfloor heating or even fabric-like wallpaper. A downside to infrared is that the panels can’t heat water, so you’ll need another method for doing that.

Other electric underfloor systems use heating wires or cables connected to your power system, rather than your plumbing, to warm the space from the floor up. This can be particularly suited to tiled floors like bathrooms and kitchens.

Warm air systems

Also known as ducted heating, warm air heating systems were popular in the 1960s and 1970s. Now they’re more likely to be found in office blocks than residential buildings.

Warm air systems suck in cold air from outside and heat it using a boiler, before sending it to different rooms in the building through ducts or vents.

District heating systems

Also called heat networks, these work in a similar way to other central heating systems but on a larger scale.

District heating systems may use a boiler to burn fuel and create heat at a central location, like a large-scale version of many of our home central heating systems. Or they may even use other heat sources like geothermal energy or the energy from waste products.

The heat is circulated to several homes and buildings in an area, meaning those homes don’t need their own individual central heating system.

What fuels my central heating system?

Whether the heat is circulated around your home by water or air, you need some sort of fuel or energy source to create heat. In the UK, that usually means burning fossil fuels like natural gas, which comes from the mains supply, or using electricity from the grid.

Gas central heating

A gas-fired central heating system is the most common way to heat homes in the UK. Provided your house is connected to the grid (and the majority are), it’s often the cheapest option.

Gas has relatively low levels of CO2 emissions compared with oil or coal-fired heating systems, although it’s not a clean source of energy.

If you have a gas boiler that’s more than 10 years old, you might want to consider replacing it with a more energy-efficient one. You could be eligible for a grant to replace a fossil fuel-based system with a heat pump or biomass boiler, under the government’s boiler upgrade scheme.

Electric central heating

Electric heating systems could be separate radiators working independently of each other, or a network of storage heaters working to make the most of cheaper off-peak electricity.

If you have storage heaters, the most economical way to use them is with an Economy 7 or Economy 10 electricity tariff. These give you a cheaper tariff during off-peak hours.

Electric heating vs central heating

Electric heating systems tend to be cheaper to install than gas systems and don’t require as much maintenance. However, electricity is more expensive than gas when it comes to running costs.

On the other hand, electric heating systems are more energy efficient than gas systems. They also offer the potential for a lower carbon footprint, particularly with the government’s commitment to decarbonise the UK’s electricity system by 2035.

And if you have the means to install solar panels to power your electric heating system, you could lower your carbon footprint and your heating bills.

What are the alternatives to gas and electric central heating?

In 2021, an estimated 15% of homes in Great Britain were unable to connect to the national gas network. And a growing number of people are looking for a more sustainable alternative to a gas boiler. Other central heating options include:

Oil-fired central heating

This is commonly used by people who live in rural areas or who aren’t connected to a mains gas supply. The oil is usually stored in a large tank outside the house and an oil-fired burner provides central heating and hot water. It does have higher CO2 emissions than gas, though.

LPG central heating

Liquid petroleum gas is similar to natural gas in that it can be burned to generate energy. But instead of being distributed through a pipe network, it’s stored in a tank in the garden.

The price of LPG is generally higher than oil or gas, but it’s a highly efficient fuel.

Biomass central heating

Biomass bridges the gap between conventional boilers and renewable heating systems. A biomass or wood heating system burns organic material, including logs or wood pellets, rather than fossil fuels.

The downside of biomass boilers is that they’re expensive to buy and need to be cleaned regularly.

Renewable heating systems

These are a low-carbon alternative to fossil fuels that take energy from sustainable sources. Options include air source heat pumps, ground source heat pumps and solar water heating systems.

What kind of boiler do I have?

There are three main types of boiler. They work in different ways:

Combi boilers

A combi boiler heats water directly from the mains and sends it instantly to the tap. They’re compact systems that don’t need a tank, so they save space.

Because they heat water on demand, they can only supply so much hot water at once. This makes them best for small to medium-sized homes with one to two bathrooms. You’ll also need good mains water pressure for a combi boiler.

Regular boilers

Also called conventional boilers, or sometimes ‘heat only’ or ‘open vent’. Regular boilers have a tank that stores hot water for when it’s needed. They also use feed or expansion tanks, normally in the loft, to store cold water and send it down to the boiler when the heating is turned on.

Regular boilers are sometimes found in older homes, but they’re not normally installed in newer homes because of the pipework and space needed.

System boilers

Also called a sealed system boiler, this is the modern update of the regular boiler. They’re connected to the mains so you can heat water as needed. There’s no need for an expansion tank in your loft, but they do have a hot water storage tank. They’re ideal for larger homes with more than one bathroom and are normally fairly economical to run.

Should I change my central heating system?

Changing your whole central heating system can be a big – and expensive – job, but in some cases it’s worth the effort and disruption.

For example, if your house is connected to the gas grid but you’re using electric storage heaters, changing to a gas system could reduce your bills and give you more control over your heating.

If you want to reduce your carbon footprint, you could consider switching to a ground source or air source heat pump, or a hybrid system that uses a heat pump alongside a traditional wet central heating system.

In other cases, especially when your boiler is coming to the end of its life, it makes sense to replace your boiler with a more modern and efficient model. That way you can save on your energy bills and lower your carbon footprint too.

And if you’re ready to replace your boiler, it may be cost effective to replace your radiators and thermostats at the same time.

But remember, it’s not just about the system you install. You’ll also want to consider how well your home is insulated to minimise costs and maximise efficiency.