Though not as roomy as a battery, Mixergy has hot water tanks than can take 10-15kW to heat up depending on temperature and size of tank. Mine runs either on a myenergi Eddi or an imemrsion heater. I would typically heat it up over night - even int he summer as the export rate at 15p is better than buying it at 7p. This export rate has pretty much made the eddi useless.
So, would you consider a Mixergy integration with their API to charge similar to a battery when extra slots are provided? Happy to test this for you.
Others have done it on Home Assistant here: https://github.com/tomasmcguinness/homeassistant-mixergy
Their web address is simply: https://www.mixergy.co.uk/
Thanks
