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Heating your water with Solar PV

Many homeowners’ express interest in utilising solar panels for heating their water. Indeed, it is feasible to achieve hot water in a property through the energy generated by solar panels by incorporating a solar power diverter into the solar PV system. It is essential to note, however, that this approach differs significantly from the method employed in a solar thermal system. These two systems represent distinct technologies, each with its own mechanisms and functionalities.

In this article, we outline the differences between solar thermal and solar PV systems. We then take a detailed look at the role of a solar power diverter in a PV system, how it works, and the benefits of using a diverter to heat the water in your home opposed to solar thermal.


Solar thermal systems and solar photovoltaic (PV) systems differ in their primary function and the way they harness solar energy.

Solar thermal systems are designed to directly convert sunlight into heat, typically for water heating. These systems use collectors to absorb solar radiation, heating a fluid that is then transferred to water for various applications. 

On the other hand, solar PV systems generate electricity by converting sunlight into electrical energy. PV panels, made up of photovoltaic cells, produce a direct current (DC) that can be converted into alternating current (AC) for use in powering electrical appliances, lighting, or feeding into the grid. While solar thermal systems are highly efficient for heating applications, solar PV systems offer greater versatility, enabling electricity generation for a broader range of purposes.

Myenergi eddi solar diverter
tarven solar energy jake syrocki 2

Jake Syrocki
Director at Tarven Solar Energy, adds:

When using a solar diverter to heat water in a home, it’s helpful to visualise the immersion heater in your airing cupboard. With an immersion heater, you can manually turn it on using electricity, which heats an element inside the water tank to warm up the water.

Now, contrast this with a solar thermal system, where the process involves heating oil inside tubes. The heated oil then circulates through a tank, transferring its heat to the water using energy captured from the sun. 

So, while both methods involve heating water, the solar diverter utilises electricity to directly warm an element, whereas the solar thermal system employs sunlight to heat an intermediary substance (the oil inside the tubes), which then heats the water in the tank.

The choice between solar thermal and solar PV will depend on specific energy needs, space considerations, budget and the intended applications in residential, commercial, or industrial settings. 

As a ‘wet’ system, solar thermal installation falls under the domain of plumbers since it revolves around water-related components and heat transfer. 

At Tarven Solar Energy, we specialise in solar PV systems and solar power diverters, rather than solar thermal system installations. Our experienced electricians are adept at placing solar panels, configuring inverters, and managing the intricate electrical components crucial for converting sunlight into usable electricity. Their expertise in electrical systems, wiring, and connections ensures the seamless integration of solar PV systems into the electrical infrastructure of homes or businesses.

flat roof solar panels with eddi solar diverter


A solar hot water diverter, also known as a solar power diverter or energy diverter, is a device designed to optimise the use of solar energy for water heating in residential or commercial buildings. The job of the diverter is to intelligently ensure that the electricity generated by your solar panels is used in the most efficient way by directing surplus electricity generated by your panels to heat water. This clever device senses when you’ve got surplus solar energy and shunts it into your water heating element instead of sending it into the grid or storing it in batteries.

How does a solar diverter work?

The solar diverter works on an export margin, so the batteries will automatically fill up, once they are filled and you’re not using power, it will then heat the element, most diverters require a minimum of 400w plus 100w export (500w total) in order to do this. Most diverters are now ‘smart’ so you can check the temperature of the water in your cylinder or boost the element in off peak times.

When your solar panels produce electricity, they send it to the solar power diverter. Instead of sending all of it to the grid or your batteries, it checks if you’re using electricity in your home right at that moment. If you are, the diverter sends the solar electricity directly to power your appliances or devices. Here’s how it typically works:

  1. Solar panels: When solar panels generate more electricity than the building needs, the excess energy is usually sent back to the grid or stored in batteries.
  2. Diverter function: The solar hot water diverter intervenes in this process. Instead of exporting surplus electricity, the diverter identifies when there is excess energy available.
  3. Water heating: The diverter then directs this surplus electricity to an immersion heater or another water heating system. This allows the excess energy to be converted into heat, warming the water in a storage tank.
  4. Increased self-consumption: By using surplus solar energy for water heating, the solar hot water diverter increases the self-consumption of solar-generated electricity within the home, reducing the need to purchase electricity from the grid for water heating purposes.
flat roof solar panels with eddi solar diverter (1)

So, instead of buying electricity from the grid, you’re using the free electricity from your solar panels for a practical purpose – keeping water warm. It’s like making sure you use all the solar power you generate in your home before sending any extra to the grid or storing it. It contributes to energy savings and a more sustainable use of solar power. Specific features and functionalities can vary among different models and brands of solar hot water diverters.

What is an eddi?

The eddi is a type of energy diverter developed by the UK-based company myenergi. It is designed to work in conjunction with renewable energy sources, such as solar panels or wind turbines. Its primary function is to optimise the use of surplus energy generated by these sources. It can be used in a variety of applications such as heating electric underfloor heating maps or incorporated into a gas boiler and air source heat pump to jointly heat a hot water cylinder. You can even heat your swimming pool!

The myenergi eddi solar power diverter specifically focuses on diverting excess energy to heat water in a home, acting as a smart controller for water heating systems as explained earlier. When there is surplus energy from renewable sources, instead of exporting it back to the grid or storing it in batteries, the eddi directs this excess energy to an immersion heater or another compatible water heating system.

Can a solar diverter be retrofitted into an existing solar PV system?

Yes, a solar diverter can either be installed at the same time as your solar panel system or retrofitted later. At Tarven Solar Energy we will retrofit to an existing system at 0% VAT.

The benefits of using solar panels to heat your water as opposed to solar thermal.

Let’s break down the benefits of using solar panels (solar PV) to heat your water compared to solar thermal systems:


Solar panels are versatile and can be used for various purposes, including generating electricity and heating water. This flexibility means you can have a dual benefit from the same solar installation.

Electricity Generation

Solar panels primarily generate electricity, allowing you to power your home or appliances. If you have an electric water heater, using solar panels lets you directly use the electricity generated to heat water.

System integration

With solar panels, you can easily integrate the generated electricity into your home’s electrical system. This can power your water heater but also other electrical devices and appliances, providing a comprehensive energy solution.

Reduced grid dependency

By using solar panels to generate electricity for water heating, you decrease your reliance on grid electricity. This can result in lower electricity bills and contribute to a more sustainable and environmentally friendly energy use.

Technology familiarity

Solar panels are a well-established and widely adopted technology. Many households already have, or are considering installing, solar panels for electricity generation. Leveraging the same technology for water heating simplifies the overall system and maintenance.


In certain situations, using solar panels for water heating can be more cost-effective than installing a separate solar thermal system. It eliminates the need for additional equipment and simplifies the overall setup.

Space utilisation

Solar panels can be installed on rooftops or other available external spaces, maximising the utilisation of available areas for both electricity generation and water heating. This is especially advantageous in properties with limited space.

While solar thermal systems excel in direct water heating applications, using solar panels for water heating offers a versatile and integrated solution that aligns with the growing trend of adopting renewable energy sources for multiple purposes within a home.

flat roof solar panels with eddi solar diverter (4)

Jake adds:

“Solar thermal can only heat your hot water tank whereas with solar PV you can use it in your house to boil your kettle, store in a battery or you can divert it to your element to heat your hot water. You can even charge your car with it. It is more versatile. 

We provide services related to solar power diverters, offering homeowners the opportunity to optimise their solar PV system for water heating. By focusing exclusively on solar PV and power diverters, we aim to deliver specialised and top-notch services, meeting the specific needs of our clients for optimal solar energy utilisation.”

If you would like to speak to Jake about installing a solar PV system within your home or business, please do not hesitate to give him a call on 020 3937 5575 Or email enquiries@tarvenlimited.co.uk for swift response.

Choose us for high-quality solar panel installation or electrical services. Getting started is as simple as contacting us on 020 8087 0216 or sending an email to enquiries@tarvenlimited.co.uk.