Otherwise known as solar heating, solar thermal technology is designed to absorb the sun’s energy to heat water for the home.
If you want to make your home more eco-friendly, a solar thermal system could be a great solution for you. As solar thermal is a renewable energy technology, installing a solar thermal system can help you to lower your carbon footprint and save you heaps of money on your energy bills. You’ll need room in your home to store a hot water cylinder and plenty of space to install solar thermal panels, which are usually sited on a roof to absorb free energy from the sun to heat your water.
How Do Solar Thermal Systems Work?
A solar thermal system (or solar water heating system) uses roof-mounted solar thermal panels (or collectors) that harness the sun’s energy to heat your water. In some cases where there is not enough roof space, the panels can be mounted on a wall or at ground level. To make the system work, a special antifreeze fluid is pumped to the solar thermal panels and this fluid heats up when exposed to sunlight. The warm fluid then travels through pipes until
it reaches the heat exchanger coil within your hot water cylinder to heat your stored water. Once the stored water has absorbed the heat, the fluid returns to the solar thermal panels to start the process again.
The hot water is stored in a cylinder, so if you shower or take a bath in the evening rather than earlier in the day, you can use the hot water that has been collected during the day. You’ll likely need a secondary source for heating water, such as a boiler or immersion heater, to allow you to increase the temperature of your water during the winter or when solar energy is not available.
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Types of Solar Thermal Panels
The two main types of solar water heating panels include flat plate collectors and evacuated tubes. We’re now going to discuss the difference between each type:
- Flat Plate Collectors: These solar thermal panels look similar to solar PV panels and
they’re the most popular type in the UK. Flat plate collectors need to be attached to
copper pipes to enable the fluid to pass through and absorb the heat from the sun,
and the collectors can either be fixed onto your roof or integrated into your roof. - Evacuated Tube Collectors: Most experts will tell you that evacuated tube collectors
are more efficient in cold climates than flat plate collectors, but they are more
expensive. These solar thermal panels consist of heat pipes that are surrounded by
vacuumed glass tubes to reduce heat loss. Evacuated tube collectors tend to create
higher fluid temperatures than other panel types and they can produce hot water
even on overcast days.
Before you purchase solar thermal panels, we recommend you contact an accredited installer who will assess your home and help you choose the right type of panels for your hot water needs.
Solar Thermal System Prices
If you want to install a solar thermal system, you can expect to pay anything between £4,000 and £5,000. Whilst the initial cost is quite high, a correctly sized system can provide around 50% of your annual hot water requirements, so it will save you a lot of money in the long run. In addition to cutting the cost of your bills, solar thermal panels can earn you money through the UK government’s domestic Renewable Heat Incentive (RHI) scheme.
The table below shows you the potential savings that could be obtained when you install a solar thermal system.
| EXISTING SYSTEM | ANNUAL FUEL SAVINGS |
|---|---|
| Gas | £60 |
| Oil | £65 |
| Coal | £70 |
| Electric | £70 |
| LPG | £100 |
All data in the above table has been sourced from the Energy Saving Trust website.
The UK Government’s Renewable Heat Incentive (RHI)
Once your solar thermal system is installed, you could be paid by the government for generating renewable energy via the Renewable Heat Incentive (RHI) scheme. If eligible, you’ll receive quarterly cash payments over 7 years. Launched in 2014, this scheme is part of the Energy Act and is designed to reward UK homeowners who install renewable heating systems.
Let’s take a look at how much money you could earn from the scheme by installing flat plate or evacuated tube solar thermal panels.
| HOUSEHOLD SIZE | SOLAR THERMAL SYSTEM SIZE | ANNUAL RHI PAYMENTS |
|---|---|---|
| 2 people | 2 m square | £215 |
| 3 people | 3 m square | £295 |
| 4 people | 4 m square | £375 |
| 5 people | 5 m square | £450 |
| 6 people | 6 m square | £525 |
All data in the above table has been sourced from the Energy Saving Trust website.
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Are Solar Thermal Systems Suitable For Every Home?
No. Although many homes across the UK will benefit from investing in a solar thermal system, some properties won’t be suitable. To know for sure, we suggest you get in touch with an accredited installer who can determine the suitability of your home for solar water heating.
Here are a couple of things to consider before you purchase solar thermal panels:
- Do you have a strong, south-facing roof?
As solar thermal panels are weighty, you’ll need a sturdy roof that can handle their weight. The best type of roofs for these panels are unshaded south-facing roofs as they receive more sunlight. That said, solar thermal panels are also suitable for south-east and south-west facing roofs, or they can be hung from a wall or installed on the ground. - Is your boiler compatible?
Some boilers are not compatible with solar water heating, such as combi boilers as they don’t need to be installed with a hot water cylinder. Check your existing boiler and whether you need to buy additional equipment, then find out how much any extras will cost to help you determine the total cost of a solar thermal system.
Will You Need Planning Permission to Install a Solar Thermal System?
It’s unlikely you’ll need to apply for planning permission to install a solar thermal system at home, but you need to know that there are some size restrictions. It’s also important to bear in mind that you may need to seek permission if you want to put solar thermal panels on a listed building, a World Heritage Site or within a conservation area. This information should be used as a guide only and you must check with your local planning authority to find out if it’s necessary to get planning permission before any work is carried out.
Solar Thermal System Maintenance
Solar thermal systems require minimal maintenance and it’s recommended that you get your system thoroughly inspected by a professional every 3 to 7 years. There are some simple maintenance checks you can do yourself to ensure your system is operating properly, such as checking for leaks throughout its life. Your owner’s manual should include a maintenance schedule or you can ask your installer to leave you with a list of simple maintenance checks that are safe for you to carry out.
When an accredited installer inspects your system, they’ll check whether the anti-freeze needs to be topped up and if the heat pump is working efficiently. The anti-freeze helps to protect your system in colder months and topping it up shouldn’t cost more than £100. In addition to the anti-freeze, solar water heating systems usually require a new heat pump after 10 years and the average cost of a replacement pump is around £90. If your system is well maintained over the years, it should last for at least 25 years.
Advantages of Solar Thermal Systems
There are many advantages of using a solar thermal system to heat your water, such as:
- Reduced energy bills
When you install a solar thermal system, you’ll be using free energy from the sun to heat your water and you can save between £60 and £100 a year on your bills. - Smaller carbon footprint
Switching to renewable energy (like solar) can dramatically reduce your carbon footprint, which means you’ll be doing your bit to help the environment. - Earn money through the domestic RHI scheme
If you install an eligible solar thermal system, you could receive payments over 7 years that are based on the amount of renewable heat generated by the system. - Generate hot water all year round
Solar thermal panels work best during the warmer months, but your system will still work all year round. In the winter, you can simply increase the temperature of your water with a boiler or immersion heater. - Low maintenance
A solar thermal system requires minimal upkeep and little regular maintenance, so you won’t need to spend a fortune to keep it in good working order.
Disadvantages of Solar Panels
Even though the advantages of installing a solar thermal system are numerous and varied, there are some drawbacks too. The disadvantages include:
- Initial investment cost
The typical cost of installing a solar thermal system ranges from £4,000 to £5,000, depending on the size of the system. This may seem high but this type of system is inexpensive to run, plus you’ll save money on your bills and you should be eligible for yearly payments through the government’s RHI scheme. - Reliant on the sun
Like all solar technologies, solar thermal systems rely on the sun’s energy to work. This means your solar panels won’t work during the evening, however, you can still use the hot water that is stored in your tank when you need hot water at night. - Still need a boiler or immersion heater
Your solar thermal system can generate 50% or more of your heated water throughout the year, which means you’ll buy less energy from your supplier and save money. But when solar energy is unavailable, you’ll still need to use a boiler or immersion heater to heat your water.