By way of comparison, the Tesla PW3 + Gateway offers full home backup and 13.5kW of fully usable battery capacity.

Yes now looking like a Tesla Powerwall3.  Not much difference in cost around £8500 for full house back up.

If you do go for a PW3, I'd recommend ditching your current solar inverter and getting the installers to connect your existing solar array into the PW3 so your solar is DC coupled to minimise unnecessary conversion losses.

Tesla are also offering a £375 rebate for orders placed before end of June and installed before end of August (although apparently it takes an age to claim):

https://www.tesla.com/en_gb/support/energy/powerwall/order/rebate#

The Indevolt allows for islanding, but it's not as "robust" as the Powerwall or the Solarwatt.

What is your goal @trebor12345? Is it having the option to island during outages? 

Yes now looking like a Tesla Powerwall3.  Not much difference in cost around £8500 for full house back up.

That higher inverter rating is actually really useful/important - being able to deliver a full 11kW to house load, including when off grid, is very flexible. We can run our 10kW electric shower completely from battery, and when cooking often find the oven (3kW), kettle (3kW) and air fryer (2.7kW) or microwave (1.5kW) in simultaneous use, all of which can be handled with ease by the PW3. I would find it extremely limiting, not to mention annoying, if we only had a 5 or 6kW inverter and ended up pulling from the grid at peak times because the inverter couldn't handle 2 or 3 things all being on at once even though you have a full battery. Can you imagine - hey dear, would you mind turning the oven off before you turn the kettle on to make gravy? That's how divorce starts!

So price up that Sigenergy system with comparable storage (so maybe 2 x 6kW if that's all you need), a 10 or 12kW inverter with full home backup and see how it compares on a like for like basis with a PW3 + Gateway (allowing for the difference in storage capacity)

BTW, I totally get if you can't get past the Elon factor, but for us the Tesla was really the only horse in the race.

If you're willing to wait till June/July, Indevolt have some interesting products coming out in the UK, and we're also collaborating with SolarWatt to install their wholesome backup solution which looks like a very polished product.

I am looking for full house back up.  I don't thing this product has this functionality.  Please let me know if I am wrong.

https://uk.trustpilot.com/review/sigenergy.com

I'd be dubious given the amount of time they have been around given their current track record. Tesla are a similar price, accepted as a premium product and have a far better (and longer) history of delivering customer support for their product in the UK.

Just my (biased) opinion. If you have total confidence in your installer to support your installation at their expense, then maybe.

The negative reviews are a worry.  I would note that some are from Australia. I have been looking at Tesla as well.

I am confident in my installer but if all goes wrong, they may not be in a position to fix any issues.

Sigenergy storage has a built-in ‘heart beat’ which has to have a response to stay alive, so very locked in to them staying in business. If they went bust then there may be no local control option to keep batteries working. It increases the consequences of the risk!

If you're willing to wait till June/July, Indevolt have some interesting products coming out in the UK, and we're also collaborating with SolarWatt to install their wholesome backup solution which looks like a very polished product.

https://uk.trustpilot.com/review/sigenergy.com

I'd be dubious given the amount of time they have been around given their current track record. Tesla are a similar price, accepted as a premium product and have a far better (and longer) history of delivering customer support for their product in the UK.

Just my (biased) opinion. If you have total confidence in your installer to support your installation at their expense, then maybe.