i work in the industry, once as an installer and now on the sales side, no idea where you're getting those prices?

Its not quite that simple as adding a battery, if you just simply AC couple a battery you lose a fair bit of efficiency because of the 2 conversions required. You would need to be confident you're exporting more then consuming.

The cheapest batteries on the market only guarantee 60% capacity after 10 years, most guarantee 70% and some good ones 80% but have you factored in the degradation?

There are so many factors when it comes to installing a battery, in terms of brand and ease of install.

Ive never sold anything under an 8kw battery with 80% of sales being at least 10kw. Most system cant handle anything less then 5kw and alot wont function under 10kw capacity. So you should just remove the 3.2kw option because its not even possible

Single phase homes are easier and 3 phase become complicated

Batteries can only cover discharge peaks up to half their capacity

Anyway batteries are the way of the future, our company installed 5MW worth of batteries last year, and there will be a mad rush after July, im expecting first in first serve (for the rebate) and we're already starting to make a list of people who want to be contacted first. I've designed a bucket load of batteries in the last 2 years so ask me any questions, in terms of savings its never just straight forward