Top Reasons Your Solar Water Heating System is not Working


My solar water heating system is not working!!!!

Why don’t I get hot water when I shower?

My electricity bill is now higher than it was before. Why is “that thing” not saving me energy?

With experience we have come across these consistent questions.

They are very frustrating questions considering you spent quite a few shillings to put “that thing” on your roof so now not only does your bank account look bad but your once beautiful roof is deformed.

If your equipment makes you feel like this then this article is for you.

angry man
In an effort to demystify the solar water heating system here is a brief explanation.

Conventional solar water heating systems trap the heat of the sun. This trapping of heat may occur by actually heating the water or heating a special chemical (in some instances they use glycol) to trap the heat and transfer it the water. That is as simple as it gets.

So why would the solar not work if the science is that simple? Here are the top FOUR reasons and the tell-tale signs of each reason.


Modern solar panels come with digital controllers which regulate at what time the electrical booster kicks in and till what temperature should the water be heated to. This electrical booster comes in handy when the heat from the sun is not enough. If the controller settings are not in line with the requirements then you will not get hot water at the required time.


  • During hot days you get good supply of hot water, however in the cold days there is no hot water.
  • The persons who shower later get hot water.
  • Randomly during the day there is hot water in the pipes irrespective of the weather.



  1. Please read the manual! Too many people have the tendency of imagining operating instructions. This can only result in wrong usage of the equipment.
  2. Adjust the start time of the booster to provide the required time to heat. Keep in mind that if you set the booster to begin at 5:30 am it is impossible to get hot water at 5:40 am. Refer to remedy 1 and check how long it takes to heat and adjust the time accordingly to your preference.


Once heated the water is stored in the solar tank. The solar tank is well insulated to reduce heat loss. Given that the storage is limited, hot water should be used sparingly. If your domestic workers are using the water for any other purpose other than bathing then you are wasting water. Don’t expect your sleek vehicles to be washed, and your lawn irrigated early in the morning using the hot water and still expect hot water for a shower.

Remember, for every drop of hot water out of the cylinder, there is an equal amount of cold water that gets into the cylinder thus cooling the water further.


  • There is random hot water availability however it is not enough to shower.
  • The early risers get a hot washer but those after that do not get hot water.
  • During the holidays, when there are no domestic workers, there is plenty of hot water


  1. Monitor the hot water usage and stop the wastage.


With aesthetics being a major concern for clients it has become quite the trend to conceal the solar tank. Unknown to the client and also the novice installer there are certain parameters that should be adhered to when installation is being carried out. For instance there is the maximum height difference between the top of the panel and the top of the tank. You need to follow these parameters.

Every other artisan is now claiming to be an expert in solar water heating installation. Whereas one may be qualified by experience they also have a tendency to let the informal assistants do the job. Wrong connection of the pipes between the panel and the tank may result in no hot water from the solar and only hot water from the electrical booster.

The distance the hot water has to travel is also a big factor. You should always try to reduce this and where it is very necessary (e.g apartments) ensure the pipes are lagged to reduce heat loss.


  • Your installer is qualified by experience. With no formal training he regularly brags about how many solar jobs he has done. He has been installing solar water heater since the 70s.
  • Some of the equipment that came with the solar panel was termed as “rubbish” by the installer. Keep in mind no manufacturer would pack “rubbish”.


  1. Only use contractors who have been registered by the relevant bodies such as Energy Regulatory Commission (ERC) and National Construction Authority (NCA).

As an aside, The Energy (Solar Water Heating) Regulations, 2012 require that a person shall not undertake any solar water heating system installation work unless the person is licensed by the Energy Regulatory Commission as a solar water heating system technician or a contractor. Default is a punishable offence.


Location here is in reference to two instances. Either wrong location within your compound or geographically.

Wrong location within your compound refers to having the solar panels in a shadow area on your roof. Direct solar radiation is required for optimal performance.

Geographically speaking if you are in an area where you hardly receive high temperatures then solar water heating may not be the best solution. This is not to be taken that all forms of solar are not applicable. Solar PV ( Photo Voltaic) is still very much applicable as you are receiving light. Keep in mind Solar water heaters trap captured ambient heat whereas solar photovoltaic capture light and convert it into electricity.


  • Since installing the system you have an absurdly high bill
  • The solar has not worked since day one.


Have a qualified technician assess your climatic conditions. In some conditions installation of solar water heating may be a waste of resources bearing in mind the roof orientation.

In conclusion the above are the top 4 reasons. Below are other reasons that affect the equipment.

Wrong sizing: Solar tanks come in different shapes and sizes. They are not a one size fits all solution. As such one needs an expert to assess the requirements and size the solar accordingly. The solar system will not match the demand.

Low quality equipment. The Kenyan market offers a wide variety of solar water heating equipment. It is important to note that though they all use solar to heat the water there are differences in quality. Again if the deal is too sweet think twice.

This article has benefited from input of two gentlemen, Mr. Ken Macharia of Tafsiri Pure Energy and Mr. Festus Kirocho of Reliable Power House who provided guidance and clarification on the information above. I appreciate them dearly.

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Using technology to improve lives. George Warutere wa Thinwa a.k.a Warutere wa Thitima is a budding electrical engineer who has wide experience in matters construction, project management, illumination design and automation. He holds a Bsc from JKUAT and a Certificate in Contracts and Contracts Management from Harvard University He spends his free time with his family and friends enjoying the simple things in life.


  1. […] This is why for instance with solar equipment the different items are rated according to their use. The tank is rated for outdoor use and so are the sensors however the controller is likely to be used indoor. This could be a reason though rare why your solar water heating system is not working. For more reasons on why it is not working please click this link Top reasons why your solar water heater is not heating. […]

  2. Not bad article. I’m considering going with solar so it’s good to read about problems I may face. Some more good information on

  3. I have installed and worked on hundreds of SHW systems and you totally missed several key reasons an existing system is not producing hot water any more.

    Assuming the install was correct (which they generally are) the most common culprits are:

    1) the sensors that control the circulator(s). 2) the circulator(s) failing 3) air trapped in the solar loop 4) loss of power to run everything 5) lack of bright sun light. Clouds can really cause problems especially in the winter months.

    Of course there are lots of other more or less obvious reasons (this is what solar techs are paid to figure out right?)

    Nice general info article over all though. But I have read better. Check out homepower . com for really good reads.

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