I pay about 38c per kilowatt plus $1.70 per day for the connection fee. So by that maths, you'd save 8×0.38=$3.04 per day. A 10kWh battery is in the ballpark of $4000. So it'll take about 4 years to break even.
Then you'd just have to pay the connection fee, which seem to be increasing every year.
The connection fee would also rise with less energy consumption/free electricity to amortize the fixed costs of the power grid.
> $1.70 per day for the connection fee
A sneaky tax that keeps rising. In the UK it pays for failed energy companies, people defaulting on their energy bills, energy bill subsidies... and supposedly for grid upgrades lol
It's risen far above inflation (responding to a sibling comment)
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>which seem to be increasing every year.
In general inflation is increasing everywhere so not completely unexpected. Also solar/battery powered networks are shaped differently than ones only powered by prime movers. The edges become thicker as power becomes generated at the edge.