Solar Hot Water

Solar water heaters use roof mounted collectors to harness solar energy which is passed to a heat transfer fluid. Heat exchangers then transfer the heat from the fluid to a home’s domestic water system where it can either be used to supplement your hot water and/or to provide central heating.


The idea here is that you use part of your roof to attach some solar panels that will produce hot water to add to your current heating system. This set-up depends upon sun and can be effective from Spring to Autumn. Many of the more modern systems use vacuum tubes. In both cases, the water from the roof is used to indirectly heat the water that comes out of the tap. The glycol (or anti-freeze) that circulates has to be changed every ten years or so.

In order for this to work for you will need a roof area – preferably facing from southeast to southwest or flat which can take 2-4 m2 of panel; ideally this should be reasonably close to your hot water cylinder. You will need a heating system that either has a hot water cylinder or allows for solar heating; and you may need to install a larger hot water cylinder than the one you already have.

Depending on the size of the system, you may need to pay out £2-6,000 including the cost of a new cylinder. This may provide savings of £50-100 annually and significant savings of carbon. How much depends on the fuel you use currently to heat your water. Grants are available through the Renewable Heat Incentive (RHI).

If you are investing in solar water heating you will be using the sun’s energy to heat your water rather than your current fuel. This is why the savings can vary so much. However, if your fuel source is coal, LPG or electricity, then for the same investment, you may do better to change your boiler or fuel source, if you can.

Geek says

  • Make sure you get an accredited installer: MCS or REAL
  • Make sure that the panels are close to the cylinder as having a long pipe run loses some of the benefit.
  • Don’t skimp on the specification or get a very small panel. The costs of changing your cylinder and getting on to the roof are similar and you’ll get better returns from larger panels.
  • Do take the opportunity to really insulate your hot water cylinder well when you change it. It will make a big difference and there’ll still be spare heat to air your clothes.
  • Don’t invest in this until you have got a really efficient boiler.

Local experiences

If you’ve installed solar heating, we’d love to hear about your experiences – both good and bad. Please get in touch!

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