Yes, a solar thermal system does work in winter. However it will be a lot less efficient than it is over the summer. For this reason you will likely need to rely more heavily on your boiler, solar immersion heater or other backup water heating system as the solar thermal installation will not be contributing the same ratio of your homes hot water.

Why is solar thermal less effective in winter?

Solar thermal systems use energy from the sun to heat water for your home. During the winter months there is less sunlight available to harness for its solar energy, especially at points where the days are shorter or skies are very overcast.

Heavy snow can also cause a potential reduction in output. Flat plate collectors are usually able to cope better with snowy conditions as light that is able to pass through the snow will heat the absorber plate - causing the snow to slide off more quickly. Unfortunately this is not the case with evacuated tube collectors as they have a form of vacuum insulation designed to reduce heat loss, so they won't produce heat to melt the snow in the same way.

Find out more about solar thermal or solar water heating.

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Can solar thermal panels freeze?

A solar thermal system should not freeze over winter. This is because indirect or closed loop systems (which are the most common choice in the UK) work by pumping a solution containing antifreeze through the collector. This solution then flows through a coil in your hot water cylinder to heat up the water for use in your home, so in actual fact no cold water flows through the collectors themselves and risks freezing.

How do solar water heaters work in rainy seasons?

Your solar heating system will be 100% water proof, meaning it will work perfectly fine even in the wettest of weather. In order for a solar hot water heater to work and provide you uninterrupted water at a decent temperature that you can use you need two things – a constant supply of water, and a little bit of sun. You will be surprised at how little sun you need to get your water to temperature – modern systems are extremely efficient.

Is it still worth installing solar thermal in the UK?

Yes. Although the heat produced by your solar thermal system is reduced over the winter months, throughout the year it can dramatically reduce your heating bills. According to TheGreenAge, a Viesmann solar thermal system could provide 60% of your hot water as an average throughout the year, with it producing around 90% at the height of summer and 25% in the winter. This can be a huge saving and is a great renewable alternative to heating all of your water using gas or electricity.

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