Quite the array you've got planned but it sounds like you're going to be well prepared for the ASHP. With our 4 kWp array, we easily get the 9.5 kWh battery full x2 during the summer months. Now it's of course different, but at least you'll be able to charge up with cheap overnight rates. Is the 5 kW inverter able to charge the batteries at 5 kW/hour or less? Otherwise, you might not be able to charge up completely overnight with only a limited amount of off-peak hours...

Posted by: @atommyk

Quite the array you've got planned but it sounds like you're going to be well prepared for the ASHP. With our 4 kWp array, we easily get the 9.5 kWh battery full x2 during the summer months. Now it's of course different, but at least you'll be able to charge up with cheap overnight rates. Is the 5 kW inverter able to charge the batteries at 5 kW/hour or less? Otherwise, you might not be able to charge up completely overnight with only a limited amount of off-peak hours...

The planned solar array is 4.2kW east and 3.2kW west with an expected peak output of around 5.5-6kW, but my understanding is the inverter has a max input of 5.4kW, so a little clipping for a few hours in the middle of the best summer days.

I believe that 5kW is the nominal charge/discharge for the inverter, so should be able to charge the batteries from empty in 4 hrs. At least, that's the theory.

In our current property (using gas and electric) we use around 16kWh/day during the spring and summer months for everything except the EV.

I'm hoping this setup should allow us to run with minimal grid usage for around half the year.

Posted by: @myheadhurts

Just wondering if that sounds insane?

It does sound quite ambitious, but I think it should be fine so long as you take measures to protect yourselves.

What happens to the deposit if the installer can't come to do an on-site survey, and then later on after the 14 day cooling off period ends they find it's not feasible?

What happens if you move in and find that work needs doing on the roof?

Do you have in writing that they'll give back the deposit if the sale falls through?

What if the purchase is delayed, perhaps to beyond when your installer will need to seek G99 approval and permission from your DNO for a car charger? It can take months for these things. Do you even know what the mains breaker of the house is? That's the kind of thing they need to know when seeking permission to get a car charger.

Your set-up sounds fine btw, I doubt there would be much clipping with an E/W array, and if there is it'd probably be on a day when the batteries are full anyway. Your max input is 6.5kW to your inverter, not 5kW. I think the max input is much more important as whilst it'll clip the difference between max input and max output (5kW), it might go wrong if fed more than the max input. You could check on PVGIS with their hourly data to see if 6.5kW is even possible (or do some simple trigonometry), but I'm guessing your installer already did that.

Also, have you considered a PV diverter for your water tank if there is one?

I wish you all the best with your purchase!

Everything you've raised, I think I've already covered with the installer.  I was asked (and the current owner allowed me) to supply various photos of the roof internal and external, info about the meter, main fuse, consumer unit etc.

The garage has it's own consumer unit, separate from the main house, with a 60amp breaker, so the EV charger will be off this.

The installer will deal wit the G99 approval having suggested that thay're typically taking around 2-3 months at the moment.

Yes, I have it in writing that the deposit is refundable should the sale not proceed.

With regard to solar divert for the water, I did wonder whether just running immersion/timer from the battery storage would be more flexible, particularly for autumn/winter on OCtopus Go for example when the isn't as much solar nevermind excess. Either way, it's not something I've spent too much time worrying about as it's not a large additional expense or inconvenience either way.

I'm trying not to get excited about the house purchase yet, as there's plenty of time for it to go pear-shaped.

@oswiu my apologies, just had a quick read of the MyEnergi Eddi manual and it seems it can be used as a timer too, so that looks perfect for almost all eventualities.