Solar thermal systems use the sun’s warmth to heat some of your hot water. Fluid inside solar collectors (panels) on your roof absorbs irradiance from the sun. It’s then pumped along pipes to your hot water cylinder, heating up the water to a preset temperature. Your boiler or immersion heater then tops up the heat as needed, bringing the water to the temperature on the thermostat. Run yourself a nice relaxing bath to celebrate – you’ll be saving money every time you turn on the hot tap.You can also now claim the RHI money on all hotwater generation.

A solar thermal system will work best in summer, when it can heat up to 90% of the hot water you use. But it will still save you money all year round and can even be designed to contribute towards your heating costs. Thanks to the government there are some tempting financial incentives too.

Step by step

We supply closed-loop solar thermal systems. This means the fluid that circulates from the panel to the hot water cylinder never touches the water that comes out of your tap. It works like this:

How solar thermal works

  1. Cold water enters the hot water cylinder from the mains
  2. Inside a closed loop, fluid is pumped up to a solar panel on the roof
  3. Fluid passes through metal pipes inside the panel and is warmed by the sun
  4. The fluid then passes into a coil inside your hot water cylinder, heating up the water
  5. A second coil inside the cylinder is connected to your boiler, and brings the water up to the temperature set on your thermostat

The technology

Every solar thermal system is made up of a solar panel (also known as a solar collector), a hot water cylinder, a pump and a controller. You’ll also need a boiler or immersion heater to back up the system.

There are two types of solar thermal panel: flat-plate collectors and evacuated-tube collectors. Evacuated-tube collectors are known for being the more efficient of the two, as they can produce slightly higher yields in autumn and spring. However, over the course of a year the amount of hot water both types of collector produce is very similar, so we’d advise you to consider the pros and cons of each before making a decision.

Glazed flat-plate collectors are good value, last a long time and need very little maintenance. They’re a good option if your home is a new build or is having a new roof, as they can be integrated with the roof itself. This gives a neater look – similar to Velux windows – and saves money on other roofing materials.

Evacuated-tube collectors have a higher efficiency than flat-plate collectors, so they may be a good option if you only have a small area of space. They can also be mounted in almost any orientation, from a flat roof to a wall. So even if you already have PV panels covering your roof, you may still be able to fix a solar thermal collector to a south-facing wall.

The ideal hot water cylinder will have a twin coil heating system, with the lower coil heated by the solar panel and the upper coil by a conventional boiler. If you have a combination boiler we’ll install a thermal store – a small hot water cylinder to store the water heated by the panels.

The speed of the pump is managed by the controller. It reacts to the temperature of the fluid in the solar collector and the water in the cylinder to automatically determine the rate at which the fluid is pumped around the system.