Should I buy an iBoost+/Eddi for a system I plan to use with PredBat?

[swythan]

I'm getting quotes for a new Solar PV & battery setup and they were suggesting installing an iBoost+ unit. On looking through here and the HA forums I've at least told them I'd prefer a myEnergi Eddi, but I'm wondering if there is any reason to spend the money if I'm planning to use PredBat for optimising power distribution.

• Can I just put a something like a Sonoff Powr3 inline with the immersion heater and use PredBat to control that with its own iBoost model?
• Is there any advantage to the Eddi over that setup?
• Is there anything useful about the integration with their EV chargers or does Predbat cover that, too?

I guess it would be useful if/when my Predbat/HA setup is broken, but I don't know what other features it has that PredBat wouldn't be overriding.

[gcoan]

The main decider will be what export tariff you are on.

If you have Octopus outgoing at 15p (or similar) and a cheap overnight rate then in most cases it will be cheaper to heat your water overnight with the immersion heater. If you have gas and on a variable gas tariff such as Octopus tracker then predbat can determine whether it's cheaper to heat the hot water on gas or electric.

In terms of controlling the immersion heater, you can't use a normal smart plug but the Sonoff Powr3 looks to be suitable as it's got a 5.5kW output rating and most immersion heaters are 3kW.

For most people an Eddi isn't worth it, you are better off exporting the electricity. There is a video I think from Gary does solar on this.

[swythan]

Thanks. It seems like I'll probably not get the Eddi then and just hook up something like a Powr3 for predbat to control. I'll get an electrician to advise on the actual device to use!

That should save me £500 I can use to put predbat/HA on singing a bit better than a RPi.

[jmfweather]

I'm on eON.Next Drive which has the following:

• Off-Peak Import at 6.7p from 00:00 to 07:00
• Peak Import at 26.32p from 07:00 to 23:59
• Smart Export Guarantee at 16.5p
• Gas rate per kWh of 6.31p

In all cases above the use of Gas is cheaper per kWh than both grid and off-peak grid. Why should I then heat water using an Eddi (which I would have to add to my system at ~£500) using solar power when I can export the same 1kW at 16.5p.

If you were off-grid for Gas, then it's a no brainer to use every lux of solar you can. If the gas rates increase to exceed any one of these costs then it's time to rethink.

[swythan]

The house doesn't have gas, as it happens. I'll be heating the water with an ASHP.

TBH I'm not sure why they're suggesting I might want to heat water with the immersion rather than just use the ASHP in this scenario. If I've got excess solar it's not particularly likely I'll be using the ASHP for heating at the time. I guess if I'm running the ASHP and still have excess then I could also run the immersion.

Anyway, I think using a simple smart switch on the immersion controlled by HA/predbat will be enough.

Thanks, both.

[gcoan]

If you've got an ASHP then even better, you'll only use a kW or two to heat the tank up overnight

[jmfweather]

An Eddi is just a glorified controller...if your HA setup can effectively control an immersion heater then that's a much cheaper solution.

I didn't see you had an ASHP so if you have that then almost none of this applies...it's probably the cheapest per kWh. For every 1kWh of electricity used to power the ASHP you get ~ 2.5kWh of heat. 6.7p overnight becomes 2.68p. 1kWh on not-exported peak solar at 16.5p becomes 6.6p which is on par with gas (which you don't have).