Does a Solar Water Heater Work At Night?

Solar water heaters have made their way into most homes owing to their cost efficiency, environmental friendliness, and well because they are the future of sustainable living. However, many people still struggle with the concept of its working and have several questions in mind pertaining to solar water heaters.

does solar water heater works at night 2

Worry not! We’re here to answer such questions and bring you one step closer to getting that solar water heater you’ve been eyeing. Wish to take a warm bath before you hit the bed at night? Confused about whether a solar water heater works at night? We are here to give you a concrete answer to your question.

First, let’s take a peek at the working principle of the solar water heater.

Solar water heaters work on heat absorption which means solar water heaters absorb solar radiation via a special coating present on the surface of something known as the collector. Furthermore, it blocks the long-wave emission of radiant heat and later absorbs the sun’s heat in the vacuum collector. This conversion of radiation into heat allows cold water to become warm.

Next in the process is water circulation. Since cold water is denser as compared to hot water, cold water is formed in the vacuum tube from top to bottom while the hot water flows from bottom to top. The water temperature in the solar water tank is increased gradually to reach a certain boiling temperature point. As for heat preservation, the hot water is insulated by an outer tank consisting of a polyurethane foam layer and stainless steel inner tank. This concept of working and heat preservation aids convenience to be able to use hot water even at night.

This brings us to our main question; does a solar water heater work at night?

The short answer to this is Yes! People who have solar water heaters or are contemplating getting one, you can definitely enjoy bathing in hot water at night despite having a solar water heater. While it is possible to use hot water, the endothermic process causing this phenomenon cannot be carried out at night.

Let’s take a look at the endothermic process necessary for the working of solar water heaters at night.

  • When the solar water heater consisting of a vacuum tube absorbs heat, the solar radiation passes via the outer tube of the vacuum tube and is absorbed by the collector coating film.
  • This heat is then transferred to the water inside the tube along the inner tube wall after which the water in the tube absorbs heat.
  • Once the water in the tube absorbs heat, the temperature rises. On the other hand, the specific gravity decreases and forms an upward power leading to the formation of a thermosyphon system.
  • The hot water continues to move upward and is stored in the water storage tank and the lower-temperature water is replenished along the other end of the tube. During this process, the temperature of the whole tank is raised to a certain warm temperature.

Take a look at this easy-to-understand illustration as an instance:

does solar water heater works at night

This blog explains how solar water heaters work by absorbing the radiation of the sun and storing hot water to be used at night. However, since there is no sunlight during the night, the radiation that the solar water heater absorbs is very weak or negligible. Hence, the collector apparatus is not able to absorb heat at night.

This indicates that if the collector of your solar water heater has been working during the day, the solar water heater can work during the evening and provide you with hot water.


Solar water heaters work efficiently and make sustainability efficient. Owing to the absence of sunlight at night, solar water heaters might not function as efficiently then and it is advised that you must avoid taking matters into your own hands as solar water heaters have a proper standard of functioning.

Get your hands on an efficient solar water heater and make your water heating bills drop by 50-80%! And because the sun is absolutely free, you also avail of protection from price hikes and fuel shortages.

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