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Central heating systems

Central heating systems make our homes warm and comfortable to live in, providing us with heating and hot water on-demand. But how do they work and what type is right for you? If you’re considering a new central heating system, or you want to make yours more energy efficient, read our handy guide to discover your options.

Written by

Sofia Hutson

Utilities expert

Posted

6 JULY 2021

4 min read

What types of central heating system are there?

There’s nothing better than coming home to a warm, cosy house when the weather is miserable, and maybe running a hot bath. And here in the UK, where the weather is often miserable, most of us are lucky enough to have a central heating system.

A central heating system uses one source of heat to warm several rooms in your home and normally heats up your water too. Central heating systems typically fall into one of a few categories:

Wet heating systems are the most common type of central heating system in the UK. They use a boiler to burn fuel and heat water, which is then pumped around a network of pipes that connect to radiators installed in different rooms of the house, or run under the floor to warm the area, allowing it to act like a large storage heater. Underfloor systems typically have a lower operating temperature than radiators, so can place less demand on your boiler. Newer, low-carbon methods for wet systems include ground source and air source heat pumps. Here, a very efficient pump extracts and compresses heat (thermal energy) from the air or pipes running through the ground and transfers it round your home. These types of systems are cheap to run, but may be more expensive to install.
Electric heating systems are the second most common and there are a few different types, including electric boilers. Electric storage heaters are commonly found in flats and apartment blocks. They use special ceramic bricks to collect and store energy at night, when it tends to be cheaper, and then release the stored heat throughout the day when it’s needed. There are also electric radiators, which work without a boiler to turn electricity into heat to warm the air in a room (like an element on your hob or in your kettle), and infrared heating panels, which use electricity to directly heat the people and objects in a room. Electric underfloor systems have heating wires or cables connected to your power system, rather than your plumbing, to warm the space from the floor up – it can be particularly suited to tiled floors like bathrooms and kitchens.
Warm air systems were popular in the 1960s and 1970s, but now they’re more likely to be found in office blocks than residential buildings. Warm air systems work like air conditioning in reverse: they suck in cold air from outside and heat it using a boiler before sending it off to different rooms in the building through ducts or vents. If you have an older home, there’s a chance you still have a warm air system.
District heating systems work in a similar way to other central heating systems but on a bigger scale. They 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. That heat is then 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, to create heat you need some sort of fuel or energy source. 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 still the most common way to heat a home in the UK. That’s because, provided your house is connected to the national grid (and the majority are), it’s often the cheapest option in terms of running costs. Also, 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.

The newer A-rated condensing boilers are very efficient and can save you money in the long term. 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 government grant to help you improve efficiency in your home.

Electric central heating

Unlike gas heating systems, that generally rely on a central boiler, electric heating systems are more diverse. They 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, which can give you a cheaper tariff during off-peak hours.

Electric storage heaters are considerably cheaper to install than gas central heating and don’t require much maintenance. However, electricity is more expensive than gas so electric boilers are only really cost-effective if you don’t have a mains gas supply. Also, they can only produce small amounts of hot water, so they aren’t suitable for larger properties.

What are the alternatives to gas and electric central heating?

It’s estimated that more than 14% of homes in Britain are unable to connect to the national gas network, while 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. Oil boilers are also used by more than two-thirds of households in Northern Ireland as their main source of heating. 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 usually delivered by road and 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. This 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, to provide heat and hot water. The downside of biomass boilers is that they are 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. If you install a renewable heating system, you may be eligible for the Domestic Renewable Heat Incentive (RHI), which can provide you with payments for the heat it produces.

Should I change my central heating system?

It really depends on your home and circumstances. 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 a network of electric storage heaters to heat your home, you could consider changing to a ‘wet’ gas-fuelled system to reduce your bills and get more control over your heating.

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. In this case it might also be cost effective to replace your radiators and thermostats at the same time, as you’ll already be draining the system to install the new boiler, and they can help maximise fuel efficiency.

We all have a responsibility to reduce our impact on the earth and the UK government is committed to reducing emissions to zero by 2050. As part of this effort, it’s been announced that the installation of new gas boilers will be banned, and ground source and air source heat pumps will be used instead. The date hasn’t been set yet, but consultations on how this should be done are underway. Some commentators are expecting that the ban could happen as early as 2025.

If reducing your carbon footprint is the main reason for changing your heating system 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. Heat pumps are expensive to install but considerably more efficient and potentially cheaper to run in the long term, especially if you qualify for the Renewable Heat Initiative. Gas boilers are set to become outdated, so this type of system has the potential to be more future-proof if you’re making the switch now.

What kind of boiler do I have?

If you’re thinking of updating your central heating system, you’ll need to know what type of boiler you have. There are three main types of boiler and they work in different ways:

Combi boilers
A combi boiler heats the 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. And because you only heat up what you need, they’re efficient too. While it can be quite slow to fill a bath, you won’t have to wait for a tank to heat up – so you don’t have to plan in advance. Typically they don’t work with power showers and because they can only supply so much hot water at once, if you use multiple hot water appliances simultaneously you’re likely to find that one is losing pressure or getting colder as the hot water is shared around elsewhere too. 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, as well as feed or expansion tanks, normally in the loft, which 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 all the pipework and space needed.

System
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 any expansion tanks up in your loft, but they have a hot water storage tank too. They’re ideal for larger homes with more than one bathroom and are normally fairly economical to run.

Frequently asked questions

Which central heating system is the most efficient?

Central heating efficiency is important – not only for the health of the planet, but also for reducing our energy bills. In the UK we use the SEDBUK (Seasonal Efficiency of Domestic Boilers in the UK) scale to rate a boiler’s efficiency, with A being the best and G the worst.

Modern condensing models are normally much more efficient, but you also need to think about what type and size of boiler is best for your home.

Although modern gas, oil and LPG boilers are more efficient, they do waste some energy in burning the fossil fuel to create heat. And that’s bad for the planet too. In a way, electric systems are 100% efficient because they don’t need to burn the fuel, so all the energy goes into heating the water and your home. But unless you’re on a green energy contract, your electricity will most likely come from burning fossils fuels, so won’t be 100% clean.

Heat pumps also need electricity to work but they can produce much more energy than they use – up to three to five times as much, depending on the model you have – which means they could be 300%-500% efficient. And they’re a better option for our planet’s future.

If your system has a hot water tank, you should make sure it is well insulated so you’re not wasting heat.

How can I change my heating system to reduce my carbon footprint?

Switching to a heat pump is one way. They’re one of the cleanest heating systems we have to date, but they are expensive to install, and they take up a fair bit of space too. If you have an electric system, you could also look at generating your own renewable electricity from solar panel or wind turbines.

Looking to the future, people are hopeful that we can use our existing systems but transition to greener sources of gas, like hydrogen – which doesn’t produce carbon when burned – and carbon neutral biogas – made from grass cuttings and food waste. But although you can opt for ‘hydrogen ready’ boilers, we’re not quite there yet in terms of infrastructure.

In the meantime, if it’s time to replace your boiler, look out for more efficient models and update to a condensing model. And before then, have a look to see what small improvements you can make in your home to improve efficiency. Little things, like improving the insulation or installing smart thermostats, can make a big difference.

Read our guide to heating your home efficiently.

How much will a new central heating system cost?

The cost of a new central heating system depends on a lot of variables, including:

what type of central heating system you have (and what type you want)
whether you need additional work like replacing pipework and installing new radiators
the cost of installation in your area
the size of your home
the make and model of your new boiler, (or heat pump)

In general, electric heating systems can be a lot cheaper to install, but they might cost you money in the long run, so remember to factor running costs and lifetimes into your calculation.