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Using your Mixergy tank with Solar PV

By David White Mar 14, 2023
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With rising energy costs, homeowners are often investing in renewable energy solutions like solar PV. It’s important to make the most of this self-generated power rather than exporting it back to the grid.

We are proud that Mixergy hot water tanks can make the most of the 100% green energy generated from your solar PV, either with our own embedded (built-in) solar diverter or when combined with a third-party PV diverter.

Heat your water for free using green energy!

We answer some of the most popular questions that we are asked when it comes to the functionality of how to use our Mixergy tank together with solar PV systems.


Can a Mixergy tank work with any third-party solar diverter?

Yes – the Mixergy tank can work with any third-party solar PV diverter – you just need the Mixergy ‘PV Switch’ (part code: MAS0086-01) included with your tank.

Some example third-party diverters include the Solar iboost+, Solic 200 and the Myenergi Eddi.

The PV Switch allows the Mixergy tanks’ immersion to accept a variable power supply from a third-party source, effectively heating the tank from the top-down.


Mixergy PV switch


Does the Mixergy tank lose any smart features or functionality as a result of connecting to a third-party solar diverter?

No. The Mixergy tank does not lose any smart features or functionality as a result of connecting to a third-party solar diverter.

Please note, however, that once the Mixergy tank is connected to a third-party solar diverter, it is the third-party solar diverter that is in control of the power supply to the immersion.

The tank cannot control how much solar to divert, it simply becomes a passive recipient of any excess solar energy that is diverted. The tank will still heat from the top-down incrementally, but you cannot stop diverting once the tank becomes 50% full for example.

If you wish to have this level of control, we would recommend using the Mixergy Embedded Solar Diverter tank option, as this provides enhanced control capabilities.


How can I control the target temperature when using a third-party diverter?

The PV Switch enables a third-party diverter to send energy directly to the Mixergy tanks’ immersion (not through the Mixergy energy meter or controls). The immersion is reliant on its manual high limit stat to determine the maximum allowable temperature, rather than the digital temperature sensor that is used for setting the target temperature in the app.

The high limit stat is set to ‘max’ in the factory. It is recommended that you adjust the manual high limit stat from max (marked ‘5’), down one notch to ‘4’, this will ensure that the tank does not overheat during longer periods of solar diversion.


What is the primary benefit of combining Mixergy with a third-party solar diverter?

The Mixergy tank has the unique ability to partially heat the tank to provide enough hot water to get you through your morning demand, this frees up as much cold water volume as possible within the tank for heating via excess solar PV during the day.

In effect, this converts your Mixergy tank into a super low-cost battery, ensuring you make the most of the solar PV your home system generates.

Mixergy can work with any solar PV diverter making the interface between systems simple and effective.


Will manually adjusting the high limit stat invalidate the tank warranty?

If you manually adjust the high limit stat to lower the maximum allowable temperature delivered through a third-party solar diverter, then no, this will not invalidate the warranty.


What is the best option if you want to determine the level of solar PV, the amount of kW’s diverted, or set target temperatures from solar diversion?

To achieve maximum flexibility, we recommend that you specify a Mixergy Embedded Solar PV tank with your installer.

Mixergy Embedded Solar Diverter

This product offers the most enhanced level of control and data visibility of any Mixergy + PV solution on the market and will allow you to optimise your system to ultimate levels of performance!

Using a Mixergy tank with a PV Switch combination (to work with an existing third-party diverter) will still allow you to maximise consumption of locally generated solar PV, but offers fewer data points and control options when compared with the Mixergy Embedded Solar PV diverter option.


Do I have to enable grid services to access Mixergy’s machine learning algorithm schedule optimisation?

No, these product features are separate – you can optimise the machine learning schedule without enabling grid services. You can also enable grid services without having to use a machine learning schedule setting.


What does the ‘grid services enabled’ setting mean?

This is where you can opt into a service that allows your tanks’ immersion to be periodically switched on to help the National Grid utilise more renewable energy.

When National Grid have an excess of renewable energy (typically wind and solar), the frequency (Hz) of our energy supply increases. In order to keep the frequency at an acceptable level (50Hz), the National Grid needs to switch electrical assets on to curtail this excess supply.

Mixergy can provide a quick response to this need in the form of Firm Frequency Response (FFR) – these events happen infrequently (once or twice per month) and typically last less than 90 seconds at a time.

The energy that your tank consumes (usually 1-2p of electricity) is stored within the tank and offset from your next scheduled heating event.


If you want to use solar PV energy for your hot water, please discuss with your plumber or installer which Mixergy tank option is best suited for you. Or check out our ‘Find an Approved Installer‘ map to search for someone who is local to you.

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