Immersion Heater PV Matched

I want to emulate this

I already have monitoring on Solar, Immersion, Grid Import/Export

However I can’t find a decent option to control the power of a resistive heater through homeassistant.

Best option I have found so far is this

Then use a sonoff 4ch-pro to switch the resistance of the control side which allow me 15 possible power levels.

Does anyone have any ideas for a 3kw heater controller? This option comes in at £50 but would take a LOT of setup to get consistently close to 0 export and I’d have a 200W step.


This might be an option if I can figure out how the input is controller.

Did you have any success with a solution for this? I am doing a solar PV setup and will have exactly this problem - a large array which I’d want to match the output to an immersion heater, but NOT spend an insane £300+ on a controller :smiley:

I am also interested how you went about this. I have sorted the power monitoring so I know how much surplus energy I can direct to the heater but I dont know how to actually control the element to match that power level.

If you can furnish a 0-10v output, then this Solid State Relay is the bad daddy you need…

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Ah thanks! I’ve just finished the first part of my solar install, and now have surplus energy coming out of my ears :smiley: That looks like a decent option, I can use a PWM to 0-10V breakout board and ESPHome to control it, and some logic to smooth slightly. Given it’s solid state I assume it’s happy to bounce the control levels around.

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Did you have any success here? I’ve ordered an iBoost but would prefer a DIY solution with more HA-based control. Thanks!

Any luck? I’m looking for similar. Suspect the iBoost won’t pay itself off by the time I need to make serious changes to my boiler situation. Really keen to get a DIY approach working. I guess the PWM approach could work, dad is an electrician and we have some good solutions - nothing like this though…

I’ve just bitten the bullet and gone for an iBoost - works well, but certainly not cheap! Also finding the need to add DIY power monitoring to it with a D1 mini + PZEM-004.

Can you give me more details about what you used to monitor the iBoost with Home Assistant? From time to time mine kicks in and decides to use the battery which is very annoying. I would like to DIY iBoost Buddy. The Buddy is also expensive, there must be a way to make Home Assistant act like a Buddy.

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I use a smart plug to monitor my iBoost in Home Assistant.
As the iBoost will only ever run at a maximum load of 3000w I have not hard wired mine, instead its on a 3 pin plug and its never been an issue in over 4 years. My household voltage runs between 240v & 250v
3000W @ 240V = 12.5A
3000W @ 250V = 12A
There are plenty of smart plugs available in the UK rated at 13A and some rated at 16A