Hi Hugo, I’m not sure I see it like that. Charging a battery with Solar means that the solar isn’t exported ( losing a potential 15p / kWh in export income). So the price of using “free” solar via battery storage is 23-25p /kWh. But doing so avoids importing those units at, say, 30p. So the monetary value of using the battery is pretty low.
That may be the 8-10p you were quoting, or it may be a different 8-10p?