What is the best solar PV option for my Mixergy cylinder?

October 12, 2022

With rising energy costs affecting homes across the UK, many homeowners are choosing to invest in solar PV panels to reduce reliance on the grid by generating their own electricity – which is fantastic! Getting the most out of your solar PV system and consuming as much of your generation as possible is the aim of the game and this is where Mixergy comes in

At Mixergy we regularly receive calls from customers asking:

  • How does the Mixergy tank work with a solar PV system?
  • What type of solar diverter do I need to connect to my Mixergy tank? And what about if I already have a solar diverter, will it work?
  • Do Mixergy offer their own solar PV diverter?
  • How does the Mixergy tank work alongside a battery?

It is these questions that this article will answer, so read on to find out…

How does the Mixergy tank work with a solar PV system?

The Mixergy tank has a 3kW immersion located at the top of the cylinder. When this immersion is connected to a solar PV diverter, this immersion receives excess solar energy that the home isn’t consuming (for lighting, the fridge, a TV, or a laptop etc.). The amount of energy that is available for the tank to use can vary considerably and change very quickly as the diverter responds to light conditions outside and domestic energy usage in real-time. For example, the tank could be receiving 100W of energy one moment, then 1.7kW a few moments later.

The Mixergy tank takes this solar energy and dumps it into the hot portion of the Mixergy tank, converting any excess energy into more hot water. The Mixergy tanks’ smart controls then monitor the temperature at the top of the cylinder and inject a steady flow of cool water to expand the hot layer for example: 10% to 11% then 12% and so on until there is no more solar energy available for the tank to use. This ensures that the tank uses as much free solar energy as possible!

Top tip: consider setting your hot water schedule to a lower volume in the morning (e.g., 25%) to maximise the available capacity of cool water that your solar PV can heat up throughout the course of the day.

What type of solar diverter works with a Mixergy tank? And what about if I already have a solar diverter, will it work?

The Mixergy tank can operate with any make or model of solar PV diverter.

The most common units found in the UK are the Solar iboost+, Solic 200 and the Myenergi Eddi. They all operate in the same way: using a circuit transformer (CT clamp) to measure the amount of excess solar that your property is generating, then sending this value to a diverter unit located in the cylinder cupboard, which is then wired to the cylinder’s immersion.

For a Mixergy tank to be connected to one of these diverters, you will need a Mixergy PV Switch. The part code for this switch is ‘MAS0086-01’. This switch converts the Mixergy tanks’ immersion from a single 3kW feed to a dual feed immersion with one circuit at 3kW and one circuit with a modulating range of 100W-3000W. This allows the tank to accept a nice wide range of energy from your solar diverter system.

Top tip: When installing a solar diverter like the Solar iBoost+, Solic 200 or Myenergi Eddi, you will need a separate dedicated 16a spur on a 20a MCB (a second dedicated power supply to your cylinder cupboard).

If this isn’t viable, there is an alternative… The Mixergy embedded solar diverter (read on to find out more!)

Do Mixergy offer their own solar PV diverter?

Mixergy do indeed offer their own solar diverter – this comes pre-mounted and pre-wired to the cylinder from our factory. This option offers all the same solar PV diversion benefits of the 3rd party solar diverters listed above, plus a couple of additional benefits:

  • The Mixergy embedded solar PV diverter does not require a separate dedicated power supply i.e. if you already have 1x dedicated power supply to your cylinder cupboard this is enough for both the Mixergy tank and its embedded solar PV diverter.
  • The Mixergy tank provides additional control options over the solar diverter allowing you to choose when to divert, how much to divert, when to cut in and what temperature to heat your tank to
  • This product is featured in ‘Appendix Q’ of SAP, which helps self-builders and developers unlock higher SAP scores on their property design. Read more on this here.

Top tip: The Mixergy embedded solar diverter requires a cat5 data cable running from the electrical services cupboard in your home to the cylinder location. This is because the Mixergy solar diverter has a wired CT clamp, not a wireless CT clamp.

If you are interested in this option, ask your installer or Mixergy sales executive for a Mixergy embedded solar diverter.

How does the Mixergy tank work alongside a battery?

For the really carbon-conscious customer opting for both a Mixergy tank and a battery is a consideration.

Typically, this product lineup is only an option for those homes with large solar PV arrays, as you need to generate a large amount of excess solar to warrant having a battery and a Mixergy tank (which is like a hot water battery)!

We often get asked how do you install both systems in the same property? Both the battery and the solar diverter use CT clamps to measure excess solar generation and send that value to the diverter or battery – in practice this means without a control strategy, both systems are in conflict and whichever responds fastest will get the excess solar energy. To make sure this doesn’t happen it is important to schedule when you’d like the battery to get the excess solar and when you’d like the solar diverter to get the excess solar PV energy. This way the two systems can operate in harmony.

The Mixergy embedded diverter, and some more advanced solar diverters will have options that allow you to set a range of parameters including when to divert, how much to divert etc. Your battery should also offer these settings too. If in doubt, ask your installer for further advice.

If you’d like to discuss your solar PV Mixergy tank options with one of the helpful team at Mixergy, please call our friendly sales team on 01865 884 343.

If you are looking for an installer to help, check out our ‘Find an Approved Installer‘ map and search for some who are local to you.