There are fundamentally two economic drivers in the PW2 business case:
- Increase in solar self-consumption (pay 0c/kWh instead of exporting excess solar and then buying it back later from the grid at a higher price than what they paid you for the export)
- Price arbitrage by time shifting grid demand, i.e. shift peak consumption that would cost 45c/kWh (or whatever) to offpeak that costs only 12c, by drawing down on the battery in the evening.
In my case so far, grid consumption is down 80%, and only 5% of that has been at peak rates. That saves a LOT of money. It’s not possible to do that without a battery. Whether it’s enough to justify the cost, time will tell.