Pros & Cons of Solar Thermal Energy

In this article, we look at the pros and cons of solar thermal energy. If you are more interested in solar energy as a whole then we have a more generic article covering that topic here.

Solar thermal energy uses the sun to heat a fluid (such as water.) The technology is mostly used to provide a domestic hot water supply. We can, however, also use it on an industrial scale to produce electricity.

Let’s now take a look at the different advantages and disadvantages of solar thermal in particular.

Solar Thermal Pros

Most of the benefits of solar thermal overlap with those of solar energy. There are however a number of unique advantages when it comes to solar thermal energy.

1. Renewable

Solar thermal energy is both renewable and sustainable, meaning it will never run out. We can use it for as long as the sun will shine – which is approximately another 5 billion years according to NASA.

Non-renewable energy sources (such as coal, oil, and gas) will one day run out. This is where solar thermal has a key advantage. We will be able to use it for heating water forever.

2. Reduces Fossil Fuel Dependency

Similar to our first advantage is the fact that solar thermal can reduce our dependency on fossil fuels. This aspect is key in helping to make non-renewable energy sources last longer for future generations to use.

Reducing our fossil fuel dependency also helps to increase energy security and shield ourselves from fluctuations in the price of a finite commodity. As we use up remaining reserves of fossil fuels, they are likely to become more expensive.

3. Solar Thermal Is Environmentally Friendly

As with solar power, solar thermal is environmentally friendly. We can use it to heat water without having to burn natural resources. This reduces the level of greenhouse gases that are released into the atmosphere.

By using more solar thermal technologies, we can help to reduce carbon emissions, improve air quality, and reduce the effect of climate change.

4. Solar Thermal Reduces Heating Bills

Just like solar power can reduce electric bills, solar thermal energy can reduce your heating bills. This is true in cases where you might use a second energy source for heating your water (such as natural gas.)

In cases where you use electricity to heat your water, solar thermal can help you save on your electric bills instead.

5. Can Be Combined With Solar PV

As solar thermal heats water and solar photovoltaics (solar PV) generates electricity, you can benefit from installing both systems. When you combine both technologies, you stand to reduce your energy bills by a significant amount.

6. Requires Little Space

Domestic solar hot water systems require little space and you will often find them installed on rooftops. This eliminates the need to install solar thermal collectors in other areas of your home (such as your garden.)

7. Cheap to Run

Whilst the installation of solar hot water systems can be expensive, they are relatively cheap to run. Whilst they do require more maintenance than solar PV, they are still a low maintenance option.

8. Established Technology

The technology is well established and dates back to 1896 when solar water heating was first invented in the United States. Whilst the first solar thermal collectors were very primitive, the technology has come a long way over the years. This website has a great article on the history of solar thermal tech.

9. Can Provide a Return on Investment

Solar thermal energy systems can provide a return on investment (ROI) over their lifetime. This is due to the fact you will save money on your water heating bills. These savings are likely to add up to more than the cost of your system.

10. Can Also Generate Power

With all this talk of domestic hot water systems, you would be forgiven for thinking solar thermal has no place in the power industry – but you would be wrong. Solar thermal power plants do exist, allowing utility companies to use the technology for electricity generation.

Power plants that use solar thermal technology will concentrate the sun’s rays to heat a fluid. The heat of this fluid will then be exchanged to water to the point where it boils. This produces steam which is then able to drive a turbine to generate power.

Due to the space that is required for a solar thermal power plant, it has no place in a domestic setting (unlike solar PV.)

Solar Thermal Cons

As with the benefits, most of the drawbacks of solar thermal overlap with those of solar energy. The technology does, however, have a number of unique disadvantages.

1. Installation is Expensive

Like solar panels, the installation of solar hot water systems is expensive. Although the technology is still cheaper than solar PV, you are likely to encounter additional expenses during installation. These expenses might include the following:

  • Plumbing work
  • Installation of storage tanks
  • Integration of heat exchange systems

Traditional water heating systems are much cheaper to install but do require conventional energy sources to operate. Unfortunately, the initial cost of solar hot water is the determining factor that puts the technology out of reach for many of us.

2. Cannot Be Used During the Night

Solar thermal systems cannot be used during the night. This is one of the main disadvantages of solar energy technologies. You can, however, store hot water for later use, but this process has its own drawbacks.

3. Hot Water Cannot Be Stored for Long

Whilst hot water can be stored, it needs to be kept up to temperature and ready for use. Domestic hot water systems use frequent cycles to keep water at a suitable temperature. The problem with solar thermal systems is that they cannot do this during the night.

As a result of this drawback, if your system has no emersion or backup heater, you will likely run out of hot water a few hours after the sun goes down. Solar PV, on the other hand, is capable of storing electricity in battery units for use throughout the night.

4. Solar Thermal Is Less Efficient in Winter

It’s no secret that there is less solar energy in the winter months than during the summer. Whilst this disadvantage applies to both solar power and solar hot water, it is even more important with the latter.

5. Limited Availability of Installers

Solar PV technology is much more popular than solar hot water. As a result, there is a limited availability of installers proficient in the installation of solar thermal systems.

Whilst this drawback is becoming less of a concern as more homeowners adopt the use of solar hot water systems, it is still applicable today.

6. Domestic Solar Thermal Systems Cannot Generate Power

Due to the land and investment required for solar thermal power, it is unsuitable for use in a domestic setting. Solar PV, on the other hand, can generate electricity for a home. This could then be used to power an electric heating and/or hot water system.


So, there we have our list of solar thermal energy pros and cons. Let’s now recap on what we’ve learned.

There are numerous areas where we can benefit from solar hot water systems. They are not only great for the environment, but they can also help to reduce our energy bills.

You should always consider both sides of the debate when choosing to invest in renewable energy technologies. The key drawbacks of solar thermal involve the upfront cost of installing the technology and the fact it is intermittent between day and night time.

Whether you are an advocate of solar technologies or not, it is clear to see that the advantages of solar thermal far outweigh the disadvantages.