[rogerthat_au]

- How long do solar panels last before you need to replace them though?

A lot of them offer warranties for 20-25 years. Most tier 1 panels are expected to last 25-30 years.

- I notice that battery prices are roughly halving every 3 years. At what point does it become cheaper to attach batteries to Indian solar plants than it is to operate coal powered plants?

At a grid level this is a complex question that I'm not completely qualified to answer because it goes into the larger question of energy mix and energy security. At a factory or building level, we are not that far - we're already offering monthly packages (in terms of cost) which amounts to 10-15c/unit of a blended rate (solar + battery). The min it breaches 8c/kWHr blended rate, this can become more permanent. I'm speculating but some of what I've seen in Li-ion and ESS flow costs we may be two years or less out.