Sunsynk Inverter more reliable than grid?

[SeaGal]

That gives me a saving of:
saving = (1*0.34+1*0.20)x180 + (5*90%*0.15)*180 = £218.7 / year = £2187 over 10 years.
But a 5kWh battery would be about £2,500, with a warranty of 10 years. It may last longer, but it will also lose capacity over time.
So it doesn't feel like a good investment for me? (and batteries are not great for the environment either)
Does my logic and calculation make sense? have I missed anything here?

£2,500?! That's a lot for 5kWh.. If you don't want to DIY.... Fogstar's 5kWh packs are only £1400 (https://www.fogstar.co.uk/collections/server-rack-batteries/products/server-rack-battery-48v-5-12kwh).

Batteries are better environmentally than the 40%+ gas usage used to push electrons around the UK network... and there's a small chance that energy prices may go up in 10 years too.

You will also save by charging said battery from (free) solar in the day. But if you have very low electricity needs, then may be of little benefit.

 

[sol4096]

Thanks for the link, that is cheap!
To be clear the £2500 I quoted were with installation (including adding a switch to isolate the inverter from the battery when needed, etc). But that is still more than Fogstar would be with installation.

Now interestingly the installer received and installed temporarily the wrong battery initially: the rack version rather than the wall-mounted one. They should both be the same spec though (https://www.sunsynk.org/ip65-battery). For some reason the BMS didn't work on the rack one.
Now they came back to replace the battery by the wall mounted one, and the BMS now works.

I was surprised to see a noticeable improvement in effective capacity, as in the battery seems to discharge slower in SoC percentage for the same load (my "idle" house during the night).
As the specs are supposed to be identical, I'm left thinking that the BMS which now works may be the reason? does it allow the inverter to optimize things much more effectively than without, to the point that a battery charge lasts visibly longer?

 

[houseofancients]

yes, this class of inverters must run with comms as it will optimize quite a few things..
without comms it works, but no "extra's"

btw there is no difference between the rack and wall mount, except there maybe some extra hardware screwed on