Eddi or iBoost?


I am seriously looking into replacing my combi boiler with a heat pump, which means I will need a tank for the first time. Since I have 3.75kW of solar PV it is probably sensible to divert excess of that into the tank.

The 2 market leaders seem to be Eddi and iBoost.

Does anyone have any experience of either, or views as to which is better, or whatever?

Many thanks,

Alan Mould

I have an Eddi. I am very happy with it. I also have a heat pump.

Bear in mind that heat pumps cannot heat your home and your hot water simultaneously. That is a generalisation based on what you can get a BUS grant for and not strictly speaking true.

My house loses heat at a rate of about 2-3kW. If I used the heat pump as the only hot water source there would be a notable reduction in indoor temperature by the time the water reached the temperature we want, so I use the heat pump to heat the water to 49°C, which still gives a reasonable COP, and then return to space heating. The final top up is with the immersion heater using the scheduler in the Eddi. This is only really needed because we are a family of five and use more hot water than I would like. We have a very cheap overnight rate for electricity, so use the scheduler to do all the hot water heating overnight. If you don’t do that you could probably just rely on solar top up from spring to autumn.

The Eddi integrates with myenergi’s zappi, giving a unified system if you ever get an EV.

@Alan_Mould I’m happy with my iBoost but wouldn’t whole-heartedly recommend it.

In isolation it works brilliantly as I wrote up here:

My issue is that I can’t control its “boost” (manual on) feature externally.

This means I can’t take advantage of very cheap electricity we often see overnight with Octopus Agile. I would like to trigger it when electricity prices are cheaper than gas prices.

There is a wireless controller with a boost button. I figured it should be possible to emulate so I asked the manufacturer Marlec for the wireless protocol spec to which they replied:

Unfortunately this information is company confidential and we are unable to assist you in this instance.

I think it has become increasingly clear that proprietary closed systems should be avoided and for that reason I don’t recommend the iBoost.

There are open source efforts to reverse engineer its wireless protocol to achieve this (and more) but I haven’t tried:

We’re installing a heat pump this year with a new Vaillant water tank and I’m not sure whether iBoost has a place in this new setup.

Hope that’s helpful!

In response to which I would say that the Eddi can be told what tariff you are on and automatically boost at the cheapest times. That is done via the web interface. I used this feature before I got a heat pump, but now I would like to do the same with my heat pump to get my hot water at a lower cost.

My home is not automated, so any such features need to be built into the individual devices.

Caveat: this function works with Octopus tariffs. I do not know whether it does with other suppliers.

My Eddi is linked to my heat pump so that when the heat pump needs a hot water boost, such as the anti legionella cycle, it calls on the Eddi to run the boost.

@paulf, does the proposed water tank have one or two immersions?

The Eddi can control the two independently but if the iBoost only controls one you could use it to heat the bottom immersion from solar so that the water temperature rises for the whole system.

As an alternative your heat pump might also have a solar feature. Mine should have but I wasn’t told it was an optional extra and getting it fitted retrospectively just isn’t worth it.

An Eddi can be set to use the immersion heater until enough power is being generated to trigger the heat pump, then as the power level drops again it shuts off the heat pump and restarts the immersion. Very smart.

Eddi all the way - designed and built in the UK!

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Thanks to everyone who replied.
the consensus seems to be that the Eddi is the more flexible option and generally people are happier with it.

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I’m glad you noted the flexibility. Even if an iBoost exactly fits today’s requirements, who knows what your requirements will be in a couple of years?