Supply-only solar thermal panels

No – solar thermal doesn’t generate electricity. Unlike solar PV, solar thermal panels harness the sun’s energy and convert it into heat which is then transferred into your home.

You can have evacuated tube solar thermal panels or flat plate collectors; evacuated tubes are thought to be more efficient that flat plate collectors. They both work by using the sun’s rays to heat a transfer fluid, usually made from water and a type of antifreeze, which is pumped to a heat exchanger inside a water tank in your home. The heat from the exchanger heats the water inside your tank, then when the liquid releases its heat it’s transferred back to the collectors to start the whole process again.

You’ll need to use your solar thermal panel system with a boiler, collector or immersion heater. This is so that the water can be stored and used for your hot water and heating, and also because in the UK, people generally need to rely on another source of heating in the winter. There are fewer sunlight hours in the winter months, so it’s not often possible for solar thermal panels to generate enough heat from the sun to get your water up to temperature.

Whatever the time of year it is, you might want to heat the water up further than your solar panels can manage. That’s why you’ll still need a form of traditional hot water heating, but you should see savings on your energy bills. If you’re currently using natural gas, you can expect savings of around £60 per year on your fuel bills, while if you’re using LPG it could be as high as £100 pr year

Solar thermal panels are panels that can be used to heat your hot water. The collectors, which are either evacuated tube panels or flat plate collectors, harness heat from the sun and transfer it to a heat transfer liquid that heats up water that is stored in a hot water cylinder. You can use a boiler or immersion heater as a back-up in the winter or to heat the water up further to reach the right temperature.

Evacuated tube panels involve a bank of glass tubes mounted on the roof tiles, and while they’re usually more expensive, they’re more efficient than flat plate collectors. They’re exactly what they sound like – flat panels that can be fixed onto your roof tiles or integrated into the roof.

Having a solar thermal system will reduce your energy bills since heat from the sun is free, so you won’t have to rely on your traditional heating as much. You’ll also be doing your bit for the environment – if you have a natural gas heating system, you could save up to 295kg of CO2 every year.

Another benefit to solar thermal panels is that you might be eligible for payments through the Renewable Heat Incentive (RHI), which is a Government scheme to encourage people to take up renewable heating technologies. As long as you have your system installed by an MCS-registered installer and you meet a few other requirements, you could receive payments of up to £525 per year for seven years. And since the average solar thermal panel system costs £5,500, you could pay off over half of your system just with these payments. That’s not even considering that you could save up to £60 a year on your energy bills if you have a gas system.

1. After the installer’s measured up, given you an estimated output and recommended some systems for you, they’ll arrange date to come to your home to install the solar thermal panels. They’ll also let you know if any scaffolding will be required.
2. Next, they will start to fit the panels, or collectors, to your roof. Stainless steel brackets will be provided with the system and they will remove your roof tiles or slates to attach the brackets to the rafters. They’ll then replace the tiles and add waterproof flashing to ensure you don’t get any roof leaks, and add the frame.
3. If you’ve chosen evacuated tube solar thermal panels, the installer will bolt the heat transfer unit to the top of the frame but not install the tubes until nearer the end. This is because the tubes start to transfer heat to the exchanger immediately, and when everything is unconnected this could damage the unit.
4. If you don’t need a new boiler with your installation, a new dual coil water cylinder, pump and system control system will be fitted. It’s best in a loft or upper floor of your home.
5. A new thermal store or hot water tank that will store the heat provided by the solar system is much larger than a standard tank but it may fit in the spot of your old one. The installer will ensure that it’s connected to the mains cold water, your other heating source (such as a gas boiler or biomass boiler), immersion heater, temperature sensors and the solar collectors themselves.
6. Next they will install the pumping station, usually near the water tank. The expansion tank will be installed on the solar thermal loop, which is usually nearby. Its job is to prevent pressure changes that could damage the system.
7. You’ll get a heat generation meter which must be MCS-certified if you want to take advantage of the RHI, and any control equipment that comes with the system will be installed.
8. The installers will then bring the system to pressure by pumping the heat transfer liquid into the system up to a pressure of around 2 bar.
9. Finally, your MCS-registered installer will register your solar thermal system so you can apply for RHI payments of up to £525 per year.
So that’s the process of installing solar thermal panels. Remember – it's always best to use a professional to install any kind of renewable technology.

There are a few trusted companies in the UK that make solar panels. While there are other solar thermal panels out there that are made by Chinese and American companies, we’ll focus on the brands with a longstanding presence in the UK since these are the panels MCS-registered solar companies are likely to recommend to you.

Viessmann, Worcester Bosch, Solar UK and Dimplex make some of the best solar thermal panels in the UK. Dimplex and Viessmann offer both flat plate and evacuated tube solar panels, while Solar UK only offers evacuated tubes. Worcester Bosch’s Greenskies range are all flat plate collectors. Viessmann’s panels come with a 5-year warranty, while Worcester Bosch and Dimplex offer extensive 10-year warranties. However, Solar UK offer a comprehensive 25-year warranty and guarantee that the panels will deliver the same level of performance for 25 years!

We’d recommend choosing evacuated tube solar thermal panels because they are the most efficient. While there won’t be much difference between evacuated tubes and flat plates in the summer, in the winter evacuated tubes are much better at taking heat from the sun than flat plates. Since our winters are long and cold with few daylight hours, we think it makes sense to go with evacuated tubes. However, if your priority is looks over maximising efficiency, you might want to choose flat plate collectors since they sit flat on the roof and look more like solar PV panels, whereas the evacuated tubes will stick out.

Yes – solar thermal can be used for central heating. Solar thermal panels work by collecting heat from the sun, either through evacuated tubes or flat plate collectors, and transferring that to a heat transfer liquid that heats your hot water. This can then be used to preheat your central heating.

You’ll need a hot water cylinder to store the water that your solar thermal panels heat up. It’s likely that you’ll need an immersion heater or boiler to heat the water further so you can use it for your central heating, and as a back-up during the longest winter months since the solar panels won’t be able to generate as much heat.

In our opinion, it’s best to use your solar thermal panels for hot water rather than your central heating. That’s because you use hot water all year round, whereas you probably won’t have your central heating on in the spring and summer, when the panels can generate the most heat. For central heating, air- or ground-source heat pumps are a great renewable option, and you can even power them with electricity from solar PV panels if you want to be as eco-friendly as possible.