Home » Solar Panels » How Solar Hot Water Panels Work

For many years, humans have strived to figure out how we can harness the power of various Earth elements. Solar power is one of the most popular energy sources that we have been trying to exploit. You are no doubt aware of solar panels being used to convert sunlight into electricity but you might not be aware that sunlight can be used in many more ways. These methods do not necessarily even require advanced technological advances to perform this energy conversion. The power of the sun can easily be taken advantage of with the use of simple machinery. For example, a frequently used method to teach children about the power of the sun is by building a solar oven. Any box can be converted into a solar oven which can get hot enough to cook just about anything. All you need is to line the inside with tinfoil and create a transparent lid to let light in. In this situation, the light from the sun is amplified by the tinfoil to create heat which is then trapped in the box. The internal temperature of the box will continue to slowly rise as long as it is kept shut. There are many other ways to capture the light and heat energy from the sun in a more sophisticated way that can benefit humans. Solar hot water panels are one such invention.

Most homes have some sort of gas or electric powered hot water tank. The water in this tank is heated up in a large amount and meted out to the rest of the house. The costs for forcibly heating up water in this fashion can get high depending on how much of it is used on a regular basis. Even the average family who is using an average amount of hot water might be interested in a new method for heating their water. The right solar hot water systems can take some burden off of the electric grid, reduce utility bills or even just be more environmentally-friendly than your current method. This is where solar hot water panels may be of use.


The basic mechanics of solar hot water systems is that water is pumped through a series of pipes that are installed on a South facing roof. There, it is heated by the sun and returned back to the home to heat the water tank. It is important to install this system on a south-facing roof in the northern hemisphere because that is the direction from which most sunlight constantly comes. In the summer months, the sun goes from east to west with the midday sun being almost directly overhead. However, for the majority of the year, the sun does not reach an apex directly above the house and instead stays in the southern quadrant. By placing the panel here, it will get direct sunlight for pretty much the entire day. The heating power of the sun is such that even in colder climates where there can be a thermal effect that reduces the temperature of the external pipes, enough thermal energy is still captured that using solar heat for your water can still reduce energy costs at these times.

There are several components that make up standard solar heater systems. As with any hot water system, even a solar powered one requires a hot water tank. This is where the home’s water is stored and heated through heat energy transfer. When you run hot water in your house it is coming from this tank and not directly from the solar panels on your roof.


The action portion of this system is called the collector. You may also know this as the solar panel. This is where the heat and light energy from the sun is captured in order to transfer heat into the water running through your pipes. There are two primary types of collectors. The more basic type is called the flat plate collector. This works much like a greenhouse or solar oven. In a flat plate collector, pipes run through a shallow metal box that is coated with a lid of thick black glass. The light and heat are collected through the glass and trapped. The light is amplified and converted into heat by the metal interior of the box. The box then heats up much like an oven so that when the water passes through the pipes in this box it is then heated up. There is also a more sophisticated type of collector which uses evacuated tubes. These tubes are completely empty, which is why they are called evacuated. The tubes also use the greenhouse type effect to collect and trap heat from the sunlight that hits them. This heat then goes to a collecting device where water flows through. When this water flows through the collecting device the heat that the tubes collected is absorbed. This water then goes to the hot water tank. An evacuated tube system tends to be more thermally efficient but can also be more expensive.

Although water is frequently used as the medium by which heat is transferred from the collector, this water is not what actually goes through your pipes. In fact, it does not have to be water that runs through the collector. Some systems use other liquids, such as oil, in order to facilitate the heat exchange. Instead of going straight into your pipes, the system fluid runs through the collector to be heated and then it runs through a separate circuit to your hot water tank. Once the heated fluid has entered the heat exchange system, it will then transfer the heat from the liquid to your hot water tank where the water in the tank is subsequently heated. The water or liquid that is used in the collector and heat exchanger never actually goes into your tank or out your faucets.


To facilitate the flow of the liquid medium between the collector and the water tank, a pump is necessary to create circulation. This pump may be powered by electricity, in which case the utility cost savings may not be as great as anticipated. There are, however, solar-powered pumps that can be used in these systems which means that they are entirely run off of solar energy. Not only is this an advantage for utility and electricity costs, but this also means that on the less sunny days the system will not run, but these are the days when you probably would not want your solar thermal system running anyway since it would not be advantageous.

The final major piece of a solar hot water system is some sort of control system. Unless you live in an environment that never gets cold there will probably be times when it does not make sense to rely on solar panels for hot water. You may even need to pump warm water through the solar panel system in order to keep it from freezing while it is not being used. In these cases, you should also have a backup conventional heating system that runs off of electricity or gas. A control system that manages both can then be used to monitor things such as temperature and flow to make sure that the right system is being used at the right time and that you can properly maintain your solar heat system.

These are the basic components and functions of the typical solar hot water panel system. The mechanics of it are fairly simple, which makes the results quite impressive. If you are having a hard time visualizing the way these panels work there are some good diagrams here. These systems can generally be used regardless of geographic location, although a backup system may be necessary for colder climates.