Can't comment on the brands you've mentioned – we had a SolarEdge inverter fitted with our PV array and it's been brilliant. Going on five years now and it's been solid. Excellent company with a great product and track record. Highly recommended, but don't know what the price difference is.

Based on your headline description, @retrobod it sounds to me as if you are being quoted for a string-inverter with two inputs.
Each side of the roof is connected to a different input on the inverter.

The maximum you are permitted to export to the grid is 3.68kW (16A per phase).

You will have 4.25kW of PV panels, but the way in which they are to be aligned means that it isn't possible for all ten to be receiving full sunlight simultaneously.

The resulting maximum export from your house isn't likely to exceed the 3.68kW.
This strategy is common, and will be approved by your regional Distribution Network Operator under G100 certification.

Before you agree to either quotation, why not complete the export application and check that your DNO agrees?
Do you know who your DNO is?

There's no charge for the application process.
You could do one for the Growatt strategy, and another for the Solax to check that either is acceptable.

I have a SolarEdge 5kW inverter but it’s limited to export 3.68kW. I also have 2x10kWh DC coupled batteries. The batteries can take everything the 6.3kWp panels throw at them. The house can take 5kW before the grid clicks in. 

The inverter is constantly adjusting to avoid importing and exporting. Around 1% import and export when living off batteries unless the ASHP is doing more work. I also have a Zappi for the car, which I charge to avoid export. The Zappi doesn’t really like a DC coupled battery at the moment, but they are working on it.

I generally manage to adjust what is drawn to avoid drawing outside the GO off peak period. Simple controlled outlets can turn things like the dishwasher on overnight.

Phil

Please tell us more @filipe

Roughly whereabouts are you in the country?
I'm interested to assess the extent of renewable energy assets in your region.

How are you 'controlling' what happens within the cheap period offered by Octopus Go?

@transparent I am UK based. The batteries are set to charge during the cheap tariff. Now spring is on the way I need to charge the batteries from the grid less. I will probably change to Agile before long or maybe Flux.

Posted by: @filipe

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The batteries are set to charge during the cheap tariff.

Yes, I understand that.
I also have this arrangement using Octopus Go.

I'm asking how you have actually implemented the battery charger to switch in when the price falls.

@transparent My installer has set the system to charge during a window from 00:45 to 4:15. Everything runs from the grid in that period even if the batteries have been fully charged. I run the ASHP and dishwasher then, and the Zappi if there is no prospect of surplus solar and I need extra range.

The SolarEdge charging time has always been accurate so I could have used the full GO period. When SolarEdge give me full control of profiles etc. I will be able to do something smarter than the installer has done. So apart from the GO period the system is set to maximise self consumption. There are good YouTube videos by Antony Dyer on how to use modes and profiles etc. 

Phil

Thanks Phil.

So your installer is knowledgeable enough to know that your Go Tariff doesn't start at 00:30GMT (UTC) and has therefore hedged your bets by opting for 00:45

I don't understand why your end-time has been inset, however.
04:30 and 1 second is the earliest at which the cheap-rate could end.

The tariff timing is unrelated to anything configured on SolarEdge's system.
Unless/until you spend time to deduce the offset for your particular house, you cannot be certain of better using the 4-hour window offered by Go.

What generation of Smart Meter do you have?

@transparent, I agreed the time of GO with the installer and we then inset it 15 minutes. I know from billing that the timing is accurate.

I have an installer with a very good reputation and had a long wait. They do listen to issues and fix them!

Octopus fitted a new SMETS2 meter because they could not use the SMETS2 meter fitted by my previous supplier. Their requirements cannot be met by all smart meters. It is Kaifa MA120.

Phil

@transparent I have pretty similar setup. I'm happy to push the Octopus (Intelligent in my case) window to the edge though (2330-0530). there's no simple (yes I know people have coded stuff) streamlined way yet that I'm aware of to take dynamic pricing into a battery setup (particularly with powerwall, which I have, as it's a closed App) so in winter I just go for charge everything - Cars, Batteries - during the cheap window and run off the battery all day.  During the various grid support windows I've already supported them by using nothing, I could have supported more by exporting if there'd been a way for them to pay me fairly for it but there isn't. can't be on a decent export tariff with the fixed night window low cost import tariffs and I'm still on a deemed export from FIT-land.

at some point in April, I turn the powerwall from the config that tells the battery to charge overnight to the  full self consumption mode one, reverting in October - November. in an ideal world this would be a gradual switch that would be partial , dynamic and next-days-solar-prediction compensated, but thats not there today.

Posted by: @retrobod

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Looking to install 10 x 425W panels; 6 on south & 4 on east.  Got 2 quotes.  One installer is proposing a Growatt inverter, the other SolaX.  Google searches for 'reviews' suggests that both have friends, both have foes ... although Growatt support seems to take a harder hit.  Both have 10y (5+5) warranty ... which is only as good as being able to contact support and getting something done ... which suggests warranties are not really worth a great deal bar the paper (soz ... IMHO anyway). 

Does anyone have 'real' experience of whether they are sensible, reasonable choice with a solid manufacturer backup?

I suppose the advantage of a cheap inverter is that it won't cost much to replace ... the Growatt (for example) is around £420.  I realise that, thinking on those lines already, tells me that I don't have much faith in either I guess ... hence the question.

Thanks ever so.  Much appreciated.

there are probably better forums than this one for solar inverter trade offs. One thing to be aware of with string inverters - they assume all panels in the string are getting the same amount of light. In my case I knew I would have variable shading across the array at different times which meant a per-panel optimised system - SolarEdge in my case - was a must.  Optimised systems cost more but you can get it back in efficiency. My solaredge sytem has constantly outperformed the installers generation estimate which was done to MCS specs. So much so that my FIT provider asked for a double-check at one point that I was't up to no good.....