Solar hot water generation diagram -

Solar water Heating

When choosing a solar water heating system, you’ll need to consider a number of factors including your average hot water usage, the area of south-facing roof available, the existing water heating system and your budget. You’ll need roughly one square metre of collector area per person in the household. Each metre of panel area will need between 30 and 60 litres of water tank volume.

If you use a less efficient collector (such as flat-plate solar water-heating panels), you’ll need to cover a larger area than if you use a more efficient collector (such as evacuated tubes). You’ll also need to select system components (such as a hot water cylinder, controls and pipe work) and choose the location for your panels considering shade, pipe runs, roof pitch and future access.

Which? magazine investigations found some salesmen using dodgy sales tactics and exaggerating the financial savings that could be made, so we strongly recommend that you do your own research first. Then compare the estimates of costs and savings you are given by salesmen against other sources of advice.

There are lots of solar-panel installers out there, so we recommend that you always collect a range of quotes to compare – visit Quotatis ( to find fully vetted solar panel installers or search for an installer on the Microgeneration Certification Scheme website (

The next part, on how solar water heating systems work, tells you about solar water heating technology and the pros and cons of getting it installed.

Types of solar water-heating systems

There are two main types of solar water-heating panels – ‘flat plate’ and ‘evacuated’ tubes (referring to the way in which water interacts with the panel). Evacuated tubes are more efficient than flat-plate versions, so are often smaller but generate equal amounts of hot water.

There are also ‘drainback’ systems. These drain water from inside the solar panel when the pump is switched off to prevent water freezing or boiling inside the solar panel.

Pros and cons of a solar water heating system


  • Solar water heating can provide you with about a third of your hot water needs.
  • According to the Energy Saving Trust, solar water heating can save you between £50 (if you have gas central heating) and £85 (if you have electric central heating) a year on your water heating costs.
  • Maintenance costs are very low – most solar water heating systems come with a 5-10 year warranty and require little maintenance.


  • Provides hot water but not electricity
  • You’ll still need a boiler or immersion heater to make the water hotter or provide hot water when solar energy isn’t available (on overcast days, for example)
  • An unshaded, south-facing location is necessary for positioning the solar panels
  • Initial costs are higher than for conventional electric and gas-heater systems
  • Solar panels can be heavy, so your roof must be strong enough to take their weight, especially if the panel is to be installed on top of existing tiles
  • The cost of a typical solar water-heating system is around £3,000-£5,000, which works out as fairly expensive compared with the savings you’ll make over its lifetime.