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Which Is Better - Solar Thermal or a Solar Diverter?

Which Is Better - Solar Thermal or a Solar Diverter?

solar thermal

Solar thermal has been popular for many years. Solar thermal panels or solar collectors are a simple technology. They work by collectors on the roof absorbing the radiated energy from the sun. This energy heats the fluid flowing through the panels which is a mix of water and antifreeze. The fluid is pumped around a sealed circuit, through the collectors and into a coil within a specially designed hot water cylinder. The hot water is then stored in the cylinder until it’s needed.

Solar thermal power is usually used for water heating though the technology can be used for space heating. It is also a very popular solution for swimming pool heating. Depending on the design, a solar thermal system supplies on average 60% of the necessary energy to meet your hot water needs per year.

A solar diverter is a device used in conjunction with solar panels to optimise energy usage within a household. A solar diverter is exactly what it says: a device through which any solar power not being used in your home is diverted to an electrical appliance, typically an immersion heater. The power heats your water, instead of being exported back to the grid. 


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Here are some of the pros and cons of solar thermal vs solar diverter:

Solar thermal Pros:

•    Solar thermal energy is both renewable and sustainable.
We can use it as long as the sun shines. Fossil fuels such as coal, oil, and gas, however, will one day run out.
•    There is a reduced consumption of fossil fuels.
Reducing our fossil fuel dependency helps to increase energy security and to protect 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.
•    There are no CO2 emissions during operation.
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. 
•    There are cost savings from using up to 60% less energy to heat water.
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. Solar thermal also has great value for businesses.
•    Solar thermal systems can be integrated into many existing systems.
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.
•    Solar thermal is more space efficient than solar PV.
Domestic solar hot water systems require very little roof space.  Because they don’t take up too much roof space you won’t need to install solar thermal collectors in other areas of your home such as your garden.
•    Solar thermal produces endless amounts of energy with low running costs.
Solar hot water systems are relatively cheap to run. Whilst they do require more maintenance than solar PV, they are still a low maintenance option. Modern systems work efficiently all year round.
•    Solar thermal 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.
•    Solar thermal is an established technology and is less complex than solar PV.
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. Solar thermal is a perfect solution for heating up water. Solar thermal can be up to 70% more efficient in collecting heat from sun rays than solar PV.
•    Solar thermal systems can also generate power. 
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.

Solar thermal Cons:

•    Installation is expensive.
In terms of the upfront cost of installation, solar thermal panels are significantly cheaper than solar PV. However, the cost to install solar PV has plummeted in recent times. Although the technology is still cheaper than solar PV, you are likely to encounter additional expenses during installation. These expenses might include plumbing work, the installation of storage tanks and the integration of heat exchange systems. Traditional water heating systems are much cheaper to install but require conventional energy sources to operate. 
•    Solar thermal 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.
•    Hot water can’t 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 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.
•    Solar thermal is less effective in winter months when sunlight is not so strong. 
This disadvantage applies to both solar power and solar hot water. However, it is even more important with the latter. There is a way round this with thermodynamic panels. A thermodynamic solar panel is a type of air source heat pump. Instead of a large fan to take energy from the air, it has a flat plate collector. This means the system gains energy from the sun as well as the ambient air. Thermodynamic panels have the potential to provide your home with hot water all year. This means you would save money as a result. The only drawback is that thermodynamic panels need electricity for the compressor. They don't need too much power, but electricity can be expensive.
•    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. It can be rather time consuming to find the right installer. 
•    Domestic solar thermal systems cannot generate power.
Due to the amount of 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.
•    Solar thermal has a shorter lifespan than solar PV.
Solar thermal will need to be replaced after 20 years.
•    Solar Thermal systems aren’t as versatile as solar PV systems.
At a smaller scale, domestic PV systems are more versatile than thermal systems, since they can power many appliances. Solar thermal is limited to space and water heating. 
•    Solar thermal systems require more maintenance. 
Solar Thermal has moving parts and glycol liquid in the system, which means maintenance requirements can be a couple of hundred pounds a year. 

Solar Diverter Pros:

•    Installing a solar diverter maximises the use of solar energy generated by your panels, reducing energy bills.
An important advantage of using a solar hot water diverter is that it can help you reduce energy costs by taking advantage of excess power that would otherwise be sent back to the grid.
•    Solar diverters can have a speedy return on investment, sometimes paying for themselves in less than two years.
The payback period for a solar diverter will vary between models, how much unwanted energy they’re diverting to heat hot water and the upfront costs charged by your local solar installer. It’s a good idea to contact a few companies to compare quotes before making a decision.
•    Less reliance on grid electricity.
You’ll need to buy less energy from your energy supplier.
•    Solar diverters save on electricity costs used to heat water.
If you install a Solar diverter, you can heat your water using free green energy lowering not only your energy expenditure but your carbon footprint. With a solar diverter installed, you may utilise 100% of your solar power, resulting in no green energy waste at all!
•    Solar diverters have a very small carbon footprint.
•    Installing a solar diverter does not affect your Feed-In-Tariff payments.
This only applies to those who are still eligible for the feed-in tariffs as the scheme closed in March 2019. If you have the feed-in tariff it will pay for 50% of the energy you create, regardless of how much energy you export. So, regardless of how much you send back to the grid or use to heat your hot water, you will still earn the same amount.
•    Your boiler won’t have to work as hard.
Solar diverters reduce the work your own home boiler has to do, allowing it to last longer.
•    A solar diverter does not have to be installed at the same time as your Solar Panel System.
As a smart add-on device, it makes an excellent supplemental investment anytime.
•    Solar diverters generally function flawlessly. 
As soon as you connect the solar diverter to your Solar PV System, it will begin diverting any excess energy produced to your immersion heater.
•    Solar diverters can be used beyond just powering hot water systems.
Depending on the diverter, they can also be used for more than one heating element including hot tubs, spas, or even pool heating.
•    Solar power diverters are usually straightforward to install.
They take around 30 minutes to install.
•    Solar PV combined with a solar diverter provides a less expensive and relatively maintenance free alternative to Solar Thermal.
Solar thermal requires you to have a water tank for the system to work. Using your Solar PV System to heat your water is a dependable alternative because there are no moving parts, and a solar diverter is a relatively inexpensive add-on.

Solar diverter cons:

•    Solar diverters require professional installation at an additional cost to the device itself.
It’s another expense to your solar system. Solar diverters cost £300 – £500 on average.
•    Solar diverters can’t be used to heat water if the property uses a combi boiler.
•    Solar diverters may not be financially beneficial for those on the Smart Export Guarantee. 
This will depend on the rate you’re getting from your energy supplier for your excess energy.
•    A solar diverter has a shorter lifespan compared to solar panels. 
They usually last approximately 10 years so will need replacing more often than either solar thermal or solar panels.
•    Solar diverters add another layer of complexity to your overall solar system setup.
•    Solar immersion diverters are able to work in conjunction with a solar battery setup

However, there is always the risk that both technologies will end up ‘competing’ with one another for the excess energy produced. Special settings within your system will enable your priorities to be set if you are operating a solar diverter alongside battery storage.
Both solar PV panels and solar thermal are great technologies that can supply you with clean green energy. Deciding which one to choose can be difficult. If it’s just hot water that you want, then solar thermal is the perfect solution for you. 

A solar PV diverter is an excellent addition to just about any solar PV system. It enables you to make the most of the renewable energy you create while also reducing the environmental impact of your household as well as your energy costs.
A professional solar panel installer will be able to give you both the advice you need and a quote that is tailored to your unique situation.

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Janet Richardson

Janet is an accomplished director and writer at The Renewable Energy Hub. Janet has worked at a senior level at a number of publishing companies and is an authority on renewable energy topics. Janet is passionate about sustainable living and renewable energy solutions, dedicated to promoting eco-friendly practices and creating a vibrant community of eco-conscious individuals and businesses seeking sustainable energy solutions.


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