Hot water accounts for around 11% of the average energy bill. So, if you’re looking to lower your energy costs and improve your carbon footprint, it’s worth considering solar water heating.
Solar water heating systems, or solar thermal systems, use energy from the sun to heat water in a hot water cylinder or thermal energy store.
Because the amount of solar energy varies throughout the year, solar thermal systems are usually used alongside a conventional boiler or immersion heater.
Most solar thermal systems are designed to provide hot water for baths, showers and hot taps only. They don’t send hot water to your radiators, so you’ll need another way of heating your home, such as a heat pump.
How does solar water heating work?
Solar water heating starts with panels or tubes on your roof, called solar collectors. Inside these panels, a liquid (a mixture of water and antifreeze) flows through small pipes.
As the sun shines on the panels, this liquid gets hot.
The hot liquid is pumped from the panels on your roof through pipes in your hot water cylinder. Inside the tank, these pipes coil around like a spring.
As the hot liquid flows through these pipes, it warms up the water in your cylinder
The water is pumped back up to the panels to be heated by the sun again, and the cycle continues.
There are two types of solar water heating collectors:
Evacuated tubes
These use a bank of glass tubes mounted on your roof tiles.
Flat plate collectors
These are fixed to your roof tiles or integrated into the roof itself.
What are the benefits of solar water heating?
Hot water throughout the year
The system works all year round. However, because the amount of solar energy varies throughout the year, it’s unlikely to meet 100% of your hot water needs, especially during the winter months.
For example, in the summer, it should provide around 90% of your hot water requirements, dropping to around 25% in the winter.
You can use a boiler or immersion heater to make up the difference.
Lower energy bills
Sunlight is free, so your hot water costs will be lower.
Improve your carbon footprint
Solar water heating uses renewable energy and reduces your reliance on fossil fuels for heating. This helps improve your home’s carbon footprint.
Is solar water heating right for my home?
To tell if solar water heating is right for you, there are a few key questions to ask yourself:
Just like solar panels, solar hot water collectors work best on a south-facing roof, or somewhere between east to west (but not north facing). You’ll need around five square meters that get direct sunlight for the main part of the day.
You don’t have to mount the panels on your roof. You can fix them to a frame on a flat roof, hang them from a wall or mount them on the ground.
If your roof is suitable for solar collectors, it’s worth considering a solar panel system for free, renewable electricity instead. To find out what might work for you, use our solar panel calculator.
Along with solar collector panels on your roof, you’ll need a hot water cylinder. Ideally this would be somewhere inside your home, but a garage or similar space can work, too. Most systems use a single cylinder, with either an immersion heater or another coil near the top that connects to your boiler. Some solar thermal systems use two cylinders – one dedicated to the solar collectors, and another for the immersion heater.
During their visit, your installer can advise on the best routing for the pipes that will connect your roof panels to the cylinder.
If you have a conventional boiler with a hot water cylinder, it’s often compatible with solar water heating. However, you’ll need to replace your existing hot water cylinder with one designed for solar water or have a dedicated solar water cylinder.
If you have a combi boiler, you’ll likely need to add a solar hot water cylinder and replace your boiler with a conventional boiler, or a heat pump.
Few combi boiler models are compatible with solar thermal systems, as they’re not designed to heat water in a cylinder.
Most solar water heating systems are considered ‘permitted development’, so they don’t require planning permission. But there are exceptions, such as if your home is:
a listed building
in a conservation area
in a national park
You should check with your local planning office to be sure.
How much does solar water heating cost?
The cost of installing a typical solar water heating system is around £6,000. Costs will depend on:
whether you choose evacuated tubes or flat plate collectors
the size of the system you want to install
How much will I save with solar water heating?
Solar water heating systems normally provide roughly half of your hot water needs, on average. The savings you get will vary throughout the year, with systems providing nearly all your hot water in the summer, but less during the winter months.
Solar thermal savings in England, Scotland, Wales
Solar thermal savings in Northern Ireland
How do I get solar water heating?
We recommend getting quotes from at least three different installers to make sure you’re getting the best value for money.
Make sure the installers you choose are certified with the Microgeneration Certification Scheme (MCS). You can find a list of installers near you on the MCS website. Under the question ‘what would you like installed?’ select ‘solar thermal’.
How do I maintain a solar water heating system?
Solar water heating installed by an MCS-certified contractor comes with both workmanship and product warranties. What you’re covered for will vary by installer and manufacturer but typically includes several years of workmanship and longer warranties for the solar collectors themselves.
Always confirm the specific warranty terms with your installer before you go ahead with an installation.
Here are some quick tips to keep your solar thermal system running smoothly:
Your installer should leave written details of any maintenance checks to carry out.
Have your system checked thoroughly every five years to flush the system and replace the fluid mix.
Consider a shorter annual service check for peace of mind. These should cost less than a full service.
Leave your system running while on holiday but make use of any ‘holiday’ functions.
Check your system control panel regularly for any warnings and contact your installer if any issues occur.
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