Mythbusting: Solar Thermal Systems

This week we are back busting some common renewable energy technology myths and with last remnants of summer still with us we take a look at solar thermal.

If you are looking to reduce your carbon footprint, cut your energy bills and have hot water on demand, could solar thermal be the renewable technology for you? Here are some of the myths you may have heard about solar thermal; busted and clarified so you can make the right decision for your project and individual requirements.

Myth 1: Solar thermal can do 100% of my hot water

Whilst this is not fact it is not entirely a fictional statement either! Solar thermal can indeed contribute to 100% of a household’s hot water requirement during the summer months with reduced contribution during spring and autumn. During winter solar thermal will contribute almost nothing.

On average solar thermal can provide between 50-60% of a household’s annual demand for hot water if correctly sized and should be used as a complementary heating source in most cases.

Myth 2: It will takes ages to pay back the initial installation cost

This indeed used to be the case and I often have calculated the payback of solar thermal around the 30-40 year mark as hot water expenditure in a home is usually so low. Now however this is not the case with the introduction of the renewable heat incentive (RHI).

Solar thermal technology now receives 7 years’ worth of payments under the government’s domestic RHI scheme and home owners can reasonably expect to get their initial investment back within this term.

Myth 3: The bigger the installation the better

Well not quite so. Solar thermal installations are “tuned” to match the hot water storage capacity of the home’s hot water tank in order to stop stagnation during summer months. Stagnation is a solar thermal installation killer and so it is avoided through correct design of the collector panels (heat source) and the hot water tank (hot water sink) wherever possible.

Myth 4: The panels only work on sunny days

Completely untrue. For more on this read last week’s blog – Solar Panels: What If The Sun Doesn’t Shine?

Myth 5: Its OK to fit and forget

Solar thermal installations are simple and only really have one moving part (the circulation pump). Nonetheless the rigours of the extreme temperatures the solar fluid goes through in a season does justify an annual maintenance regime to check the fluid quality and to make sure the solar pump is not suffering.

Unfortunately a solar installation is only as good as the fluid and the efficiency of the moving parts so it’s well worth keeping a weather eye on some simple installation details to avoid rising energy costs.

Myth 6: Simple enough for plumbers to install

The installation of solar panels is fairly simple and with panels being sold at building and plumbing merchants its temping to get your resident plumber to fit the system. It’s always best practice and safest to get a micro-generation certification scheme (MCS) qualified product and installer to fit it.

Solar systems can be very dangerous if fitted incorrectly and with MCS accreditation you can get money for the government too. Why risk it?


…And so another week of myth busting comes to an end. Have you heard of any other untruths? Leave a comment if you have.

Doug Johnson

Doug is a chartered mechanical engineer and has had the pleasure of being involved in the UK renewable sector since 2008. With wide-ranging operational and design experience in both the domestic and commercial sectors across a wide range of recognised technologies he hopes to be able to share his experience to help enlighten and save you hassle along the way.