You will now understand that it is the storage of the electricity produced by your solar panels which has become the important issue of the moment.

The amount you get paid for exporting to the grid has been falling over the last 20 years from 53p per kWh to as low as 4p.
You may want to discuss this with your Installers who have provided quotations.

It is very unlikely to be viable to install solar panels if you intend offsetting the capital cost against 'profit' from the Smart Export Guarantee (SEG).
There's no longer any profit to be made.

It all depends on why you feel that now is the time to install 4.25kW of solar panels.

Please do discuss this here.
We are particularly tolerant of points being raised by those who do not yet understand the principles. 🙂 

we then inset it 15 minutes. I know from billing that the timing is accurate.

The timing is 'accurate' for you only because the offset being applied by your Electricity Smart Metering Equipment (ESME) falls within the first 15mins of the half-hour billing periods.
That is true for about 83% of users with Smart Meters.

The following graph demonstrates how the randomised timing system will be perceived by a notional set of 4000 users with Smart Meters.

If the random number seeded into your ESME during manufacture had instead created a greater Randomised Offset to your Tariff Switch Table, then you would be paying for a portion of the electricity at the peak rate whilst recharging your batteries from 00:45.

That's why I wrote that your installer had "hedged your bets".
He guessed that the Randomised Offset applied to your Tariff Switch Table would be in the 83% of the population.

In your case he was correct.

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

I don't think anyone has coded this.
To do requires access to data held within the ESME.

That data is within the Secure Perimeter of the meter.

Writing code to access that information requires being a Party recognised by the SEC.

There is no SMETS command which can be transmitted across the National Smart Meter Network which allows remote access to data within the Secure Perimeter.

It is not possible for an Energy Supplier to know the time at which your Smart Meter commences a half-hour period with a cheaper tariff.

I have used terms in writing the above (italics), which are defined within the Smart Metering Equipment Technical Specification 2013/14.
This is in an attempt to have clarity, rather than to be obtuse!

Please feel free to ask for further explanation if you wish.
I'm happy to do so, provided it does not compromise the security of the UK energy supply.

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.....

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.

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

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?

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

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.

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?