What would be the purpose of this new PV array (e.g. trying to extend the time where the heat pump can be run off solar, or maximise income from an export tariff)? You already have quite a significant PV setup, so getting the DNO to agree to more export power (or export equipment) may be tricky.

Have you tried to model this scenario in an online tool (e.g. easy-pv, or else the Solaredge Designer)? This might give a better idea about the benefit of micro-inverters of optimisers, although I guess that it may not offer great RoI (and tie you into a specific ecosystem).

@chickenbig I should have been clearer! This is a separate house that has no solar or batteries currently. I'm hoping DNO will accept around 6.5kw array?

Majority of solar prod will of course be in the summer when ashp not in use but I would hope that we can use a decent part of production in shoulder months and export excess using Octopus Fixed 15p

Posted by: @tim441

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This is a separate house that has no solar or batteries currently.

That makes life a lot easier!

I still think that modelling the roof and shading is the only way to assess whether micro-inverters or optimisers are worth it. You could try hiring someone to perform (and explore) the design. A quick internet searching reveals fiverr and upwork as freelancer platforms, but have not used them. The advantage of this is you could explore many different options rather than be limited by what an actual installer favours.

Is there a particular reason you would favour an all-in-one system? If cost is of concern can I point you to the posts about the DIY Mason Battery 🙂

@chickenbig thanks for thoughts! I will initially talk to installers as well as gathering input here etc. I guess its possible such independent 3rd party input would help - overall I think my scenario is relatively straightforward but definitely want to check I'm not missing something that I come to regret! Clearly no point in adding optimisers if unnecessary but equally would not wish to find out later I should have done it.

I guess my objectives are a mix of maximising solar for home use inc ASHP & EV as well as wishing to have EPS.

AIO has advantages of easier/quicker installation, fast charge/discharge rates as well as whole home EPS. Obviously on a long outage we would need to reduce draw to keep it going - so would switch off ashp if it looked like an issue.

I don't think I have the knowledge/skills/confidence to take on something like the Mason - even though the costs look impressive! 

Posted by: @tim441

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AIO has advantages of easier/quicker installation, fast charge/discharge rates as well as whole home EPS.

To be fair, hybrid inverters can offer this, and without locking you into a single battery supplier. AIO systems are hybrid inverters and batteries in matching clothes. Having gone through the ordeal of getting a Sunsynk inverter and Mason batteries to work together, I think most of the problems were caused by the installer (poor installation, absence of configuration of firmware and inverter settings, poor configuration of other things). Sunsynk technical support were helpful, although their documentation and product naming were unhelpful. I'm strongly considering getting an 8kW Sunsynk Ecco inverter (and two Mason batteries) for my own home.

A half-way-house between Seplos Mason and AIO is the rack-mounted battery. This is potentially double the price per kWh (e.g. Fogstar https://www.fogstar.co.uk/collections/server-rack-batteries/products/fogstar-energy-48v-15kwh-rack-battery-bundle which has heated batteries, or else stringing together Pylon batteries).

It may be (financially) worth splitting the contract for installing the PV and inverter (and grid/backup connections) from the installation of batteries, even if there is a 20% VAT penalty. Perhaps @sikorsky92 has a price-list they are able to share with you as from their comments they seem to be a Mason builder/installer.

And coming back to "any other AIO to look at", have you seen Livoltek? From the datasheet there are different inverter powers, and batteries can be added in 5.12kWh chunks. https://www.youtube.com/watch?v=A513FwteZjU makes some interesting points about this product which was (is?) still under development.

If you do decide to include optimisers, it would be worth comparing the current warranty coverage of the different options.  For example, Tigo TS4 are only 25 years if combined with their CCA/TAP remote monitoring system.  TS4 used without internet connection is 5 years.

The CCA/TAP remote monitoring system is warranted for 5 years.

@chickenbig thanks.. i will take a look. Lots to learn!

@skd its a good point

I had a small Solaredge system installed in 2015... Installer never properly registered the system and did not setup monitoring... and gone bust.

When i realised earlier this year (after a year!) that prod was down i went on big learning curve. Setup the monitoring ... and found one optimiser had failed. In fairness Solaredge were very helpful and replaced under warranty. Since then a 2nd failed and was replaced as well. Luckily easily accessible from flat roof so managed to do it myself.

So yes, warranty definitely worth looking at.

Posted by: @tim441

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warranty definitely worth looking at

And one which pays for scaffolding to access the faulty equipment! Having said that, some SolarEdge installers place the optimizer in the loft space;

although this is in a garage so may not get as hot as in a loft. Web-searching for SolarEdge failures in Australia makes for some interesting reading, although their heat is more extreme than here.