Someone else linked this battery earlier: https://signaturesolar.com/eg4-lifepower4-lithium-battery-48...

5kwh for $1500 with 3000 cycles is $.10/kwh. I'm oversimplifying here as the real cost is higher, but the arbitrage opportunity only has to offer ~$.20/kwh to be generally profitable with a battery like that.

Some time of use plans are already there daily. I don't think the person taking advantage of this sounds like any "kind of idiot".