I do something very similar here in Australia with a company called Amber electric
They expose us to the Wholesale spot price market on a 5 minute basis with 30 minute settlement periods.
We have a large Solar and battery system and arbitrage the grid with the batteries.
During winter (now in Australia) we actually change to a fixed price provider and then in Spring Change back to Amber again
Basically their API provides pricing data similar to what you have outlined.
What i did was work out what a roundtrip on a battery charge and discharge cycle costs me (in terms of maintenance and wear and tear) on the battery pack and then aim to exceed that.
Where it become tricky is that you have to look ahead also to make sure you do not drain your batteries too far so you are then exposed to the spot market price also.
Let me know what specific info you want and i will see what i can do
Craig
