Sunset over Solar Panels

All About Solar Immersion Diverters


"Did you remember to switch off the immersion?"

This is a question that is heard in Irish houses, constantly.

And, with good reason. Electric immersion is an expensive necessity in Ireland. Whether it is for doing the dishes or for having a shower - the immersion is called upon as a backup to oil or gas heating. Below, we take a look at immersion diverters and discuss why they are a good fit for solar PV panels.

What is a solar power immersion diverter?

A solar immersion diverter is an electronic device that is connected to the immersion. It switches on your immersion to give you free hot water when your solar panels are generating more electricity than your house needs.

How does an immersion diverter know when I am generating too much electricity?

More often than not, your solar panels will generate more electricity than your house is using. This electricity will be lost to the national grid unless otherwise captured to your immersion tank or battery. A CT (Current Transformer) clamp is fitted to your fuse board. It is a special device that is able to detect when an attempt is made to send excess electricity is being sent back to the grid.

When the CT clamps sees this export, it will switch on the immersion to consume that exact amount.

How does a solar immersion diverter work?

  • 1. The solar immersion diverter works by constantly monitoring the electricity usage in your home. This is monitored by the CT sensor clamp.

  • 2. When your home is exporting electricity, the CT clamp tells the immersion diverter to send the surplus power to the immersion tank.

  • 3. The immersion diverter device effectively heats your hot water cylinder for free, off the energy from the sun, reducing your reliance on electricity gas and oil.

  • 4. When the demand in your house increases or the solar generation decreases, the immersion diverter will recognise this and reduce the amount of electricity that it is sending to the immersion.

How much money can you save with a solar panel power diverter?

With an immersion diverter and a solar PV array, you should have free hot water from April to the end of September. Depending on your solar system size, how you heat your hot water and how many people are in your house, the savings can be up to €500 for a family of 5.

How much energy can my hot water cylinder store?

Think of your hot water cylinder as a thermal battery. A well-insulated standard 120 litre cylinder can store between 8kWh to 10kWh of energy.

Should I get a solar panel power diverter?

If you currently use fossil fuel to heat your hot water and have solar PV panels, then yes you should.

Can a solar immersion diverter work with batteries?

They both work in the same theoretical sense, by diverting the surplus energy for use at a later time. This can lead to both technologies "fighting" each other. The MyEnergi Eddi immersion diverter has a setting to incorporate battery storage on the site and will work well in conjunction with the battery.

Can I still use my immersion as normal for hot water?

Yes, indeed. All good immersion diverters have a boost functionality and timers to turn on the immersion if the water is not hot enough. For example, for showers in the morning, you can schedule the immersion diverter to come on to ensure you have enough hot water for the morning and hopefully, the solar panels have preheated the tank from the day before.

What if my tank does not have an immersion element?

You can add a device called a Willis heater. This is attached to the pipework outside your tank and effectively does the same job as an immersion heater.

This can also be worth considering where your immersion element heats only the top section of your hot water tank, which limits the amount of hot water that can be created by your solar panels.

Legionella - Why it is important to boost your hot water once a week?

Boosting your hot water to 65 °C is very important to remove the risk of legionella build-up in the hot water tank. A good immersion diverter will have this functionality built-in, but it is no harm to manually boost to make sure.

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