Dead Immersun - new battery?

Trentenders

The Immersun solar diverter that heats my immersion from excess solar has died, and so I'd appreciate your guys' opinions on what I should do...

Background info:

Solar panels with deemed export FIT payments (2014 install).
Small EV as a 2nd car that isn't used much, with Zappi charger.
Agile electric tariff.
Bottled LPG for heating
Not massive electric or water users
I have an electrician in the family, so install costs aren't an issue.

Heating my water from LPG is presumably going to cost a fortune, and our previous setup worked well, but would it make sense for me to use my situation to replace the Immersun with a on/off switch, and then have a battery installed for excess solar?

I'm thinking a battery would be more cost-effective over time, as I'd be able to make more use of my solar and cover the peak 4-7 electric rates with cheap/free power. Does that sound like a plan?

If so:

Any recommendations for battery set up - and might I need a new inverter (which wouldn't affect my FIT)?

Any ideas for not having to manually switch on the water heater when rates are cheaper every day or two (not essential, but it would be nice to have an option for it to switch on in the early hours, because I'm not waking up to do it then)? Some sort of smart switch?

Any recommendations for a solar diverter to my immersion, if I'm wrong and that would still be the best option?

Or should I just stick an on/off electric switch on the immersion, and then try and heat the water when it's sunny/when electric rates are cheap?

Value/cost over time is my main driver, with ease of use/control second. I'm overly concerned about being green, but I like using as much of my generated solar as I can.

All suggestions welcome. Thanks in advance.

Screwdriva

Do you plan on replacing LPG with a heat pump in the future? If so, may make sense to take advantage of the BUS government grant and replace the LPG boiler and solar diverter with a heat pump that will do everything you need more efficiently.

It's likely you'll need a 10+ kWh battery to realize savings on the system over your current set up so makes sense to start there. The fact that you're on a FIT tariff compounds this btw. 

P.S. If you decide to keep everything as is, the Eddi is the best diverter on the market.  

Trentenders

Thanks for taking the time. I hadn't really thought about a heat pump, but that might be something for the future, so it looks like I'd do best from a battery solution.

Ive noticed a few other threads, so I'll start reading through those for battery suggestions.

greenbee

I've got an Eddi diverter, and it has meant no oil usage during the summer, and hopefully makes a difference to oil usage the rest of the year. 

Trentenders

If it broke though, would you replace it, or go for a battery instead? I think of my immersion as being like a <3kwh store

greenbee

I've got a battery as well as the Eddi - the myenergi app is set up so that the inverter charges the battery first, then any additional spare generation goes to the hot water, and once they're both done it sends the excess to the grid. If I use hot water while there is generation, it tops the tank up again to keep it up to temperature. 

Magnitio

Not sure if this helps, but I installed a low powered immersion heater rated at 1.4kW and control it with a Tapo P110 smart plug. It's set to come on overnight on cheap rate and then a couple of times during the day. If we've used a lot of hot water, it's easy to turn on again for a while using the app or asking Alexa (other virtual assistants are available). However, we do have a battery. The other benefit of using the immersion is that we can run our boiler at a lower (more efficient) temperature as it only has the single thermostatic control.

greenbee

I'm thinking of talking to my heating engineer about this - the oil boiler is running hotter than ideal for efficiency because of his insistence on the heat for legionella. It also means that the hot water can be scalding if people aren't paying attention - so not ideal for oldies/kids. So I'm thinking a weekly 'superheating' session via the immersion could be the answer. 

Trentenders

Eddi now bought, and 10kwh+ battery solutions being looked into. Thanks all.

Solarchaser

Trentenders said:

Eddi now bought, and 10kwh+ battery solutions being looked into. Thanks all.

As someone with an eddi, id highly recommend the additional pcb and buying a couple of pt1000 temperature sensors to go into the input.

I use my eddi as the heater control for the house heating and it works very well.

The two relays on the additional board can be used as a destratification pump control, or heating control for overnight hearing etc