Can Solar Water Heaters Work on Cloudy Days?

Tue, 23 Nov 2021


Malaysia is among several countries leading the way in rapidly embracing solar energy as an alternative power source for home water heating systems. This is in a bid to reduce reliance on traditional energy sources that lead to an increase in carbon emissions and energy bills. Solar water heating systems are also gaining huge traction in Malaysia. 

Despite the growing usage of solar water heaters, there has been a lingering question over whether they still work on cloudy days. In this post, we will answer this question—as well as address how a solar water heater functions on cloudy or rainy days.


What Are Solar Water Heaters?

A solar water heating system utilises solar energy to heat the water that runs in a building. Solar panels are installed on a surface that provides direct exposure to sunlight, often the roof. Once the water is heated, it is stored in a tank, from which it circulates throughout the house.

The body surface of the hot water system is lined with collectors, where water is pooled and heated by the sunlight before being circulated back to the storage tank. Every solar water heater on the market works this way.


Do Solar Water Heaters Work on Cloudy Days?

Many people are skeptical over the functioning of solar heater systems on cloudy days, when less sunlight is available. However, the fact is that solar water heaters still provide users with hot water on cloudy or even rainy days. An overcast atmosphere does not completely block out solar radiation; the majority of sunlight still gets through the clouds to fall on the solar water heater collectors and deliver hot water to the user.

However, because of the decreased availability of sunlight, the solar water heater does not deliver maximum output. If the cloudy weather is prolonged, the solar water heater will work less and less effectively over time as available sunlight decreases. 


How Does the System Perform on Rainy or Overcast Days?

The good news is that the solar heating system can be paired with an electric backup to keep reliable hot water available on overcast days. The electric system can be switched on if the water temperature from the solar water heater drops below a certain point.

Note that the electric system should be switched off when the cloudy days are over; it's only there to boost the operation of the solar water heater. 


How to Maintain Solar Water Heaters

Carrying out maintenance of solar water heaters is essential to keep them running effectively on overcast days. Regular maintenance also maximises your return on investment. Below are a few tips on how to take good care of your solar water heater.


  • If the exterior of the solar water heating system is painted, you should repaint it every 2-3 years to keep corrosion away.
  • Always ensure that you repair leakages when they occur.
  • The collectors of a solar water heater should be regularly cleaned to remove dust from the surface and prevent scaling.


Final Takeaway

A solar heater system is a smart and cost-effectively way to make hot water available in your home. Users can enjoy them on cloudy days, although not as they would on sunny days. Installing the right solar water heater and pairing it with an electrical system is vital to ensuring that it functions optimally year-round.

Last but not least, one way to make the most of the benefits your solar water heater has to offer is to be sure that you carry out routine maintenance. This will maximise the power output of the system on cloudy days. For more information, feel free to get in touch with our professionals