The iboost will just divert PV energy to the immersion so is completely separate to your Ecodan, however, its heating your HW at a COP of 1 rather than ~2.5 for the Ecodan so not sure why you would want it?

What do you do with your excess PV currently if you get export payments for it then iboost is of even less value.

Sounds to me they have one lying around and demand is waning for them as batteries are far more useful so its poor compensation value to you and little loss for them.

@gary At the moment excess is exported.  Not getting paid for it yet though.  The installation is so recent we don't yet have the MCS cert'.

Whilst it's heating at a COP of 1 there is no cost if it's straight off the solar whereas even at a COP of 2.5 there's still a charge for the electricity. Or am I missing something?

@morgan I assumed you would be heating HW by the ASHP when you were exporting PV so no cost there and it would use less.

will they let you keep one or both of the smaller batteries that’s better compensation

@gary, I do not wish to keep either of the smaller batteries, and I can't keep just one. They are a bit like hard drives in a multi-drive NAS and must be added in equal capacity.

Posted by: @gary

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however, its heating your HW at a COP of 1 rather than ~2.5 for the Ecodan so not sure why you would want it?

It may heat at a CoP of one, but it can take the cylinder to 65 to 75 degs, then it doesn't need to heat the next day at all. This summer has been lots of rain and cloud, so next day the PV output could be rubbish, so you end paying to heat water. I hate giving my PV energy away, so would rather save a cylinder heating cylinder via heat pump when I can.

Assuming you'll be paid for your export at some point, why can't you run the ASHP for HW while solar PV is generating? You get hot water for free, and you maximize your revenue from solar export. 
Am I missing something?

Posted by: @morgan

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I have been offered the supply and installation of an iBoost free of charge by way of compensation for a bad battery installation.

Back story:  We had solar panels and two batteries installed recently. Seems to work well however we have just discovered that instead of 2x 10.1KW as specified, 2x 5.7KW batteries have been installed. No point going into detail as to who might be blamed for this cock up but the installer, whom I tend to trust (at this stage), has offered, at our insistence, to replace as per spec' and by way of compensation supply and fit an iBoost.

The info I request from those of you in the know is, is the iBoost compatable with my existing ASHP install. Mitsubishi Ecodan 11.2 ASHP and Tempest 250L DHW tank.

TIA for any advice offered.

Morgan.

I suppose that much depends upon how you intend to use your heat pump, solar PV system and batteries, along with your electricity tariff.

The main benefit of a power diverter, such as the iBoost, is that it only diverts the excess solar generation and does not draw power from the grid, though it is possible that it could draw power from your batteries.

From a cost effective aspect it is cheaper to heat your DHW by means of the heat pump, provided that there is adequate solar PV generation to run the heat pump without drawing power from the grid. On intermittent cloudy days the solar PV generation is likely to fluctuate, so it may be that there is sufficient power to operate the heat pump during some periods, but when a cloud comes along the heat pump may then be drawing some power from the grid.

Also heat pumps often use the immersion heater to perform the final stage of the legionella cycle, so once again could be drawing power from the grid.

To fully utilise your solar PV generation it would probably be more beneficial to heat your DHW via an iBoost, whenever there is adequate solar PV generation available, thereby minimising the use of the heat pump.

Obviously if you are on a TOU tariff that includes an export payment it may be more cost effective to export any excess solar PV generation and use your heat pump, powered by your batteries to produce DHW.

@derek-m LOL what a conundrum. And I hoped the decision would be easy. 😆

Posted by: @morgan

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And I hoped the decision would be easy. 😆

Your getting it free  - where is there a decision. If you paying for that would be different.

@Morgan I've covered the immersion vs. heat pump decision making process in this piece which you might find helpful: https://renewableheatinghub.co.uk/are-solar-diverters-necessary-for-homes-with-ashps-and-solar-pv-2

Posted by: @morgan

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@derek-m LOL what a conundrum. And I hoped the decision would be easy. 😆

It's those pesky clouds that cause all the problems. Well that and the Earth insisting on revolving.