Using a big battery in this way under a time of use rate isn't arbitrage, its exactly what the utility company wants you to be doing. That's why they incentiviz

Using a big battery in this way under a time of use rate isn't arbitrage, its exactly what the utility company wants you to be doing. That's why they incentivize you to do it with a nice rate. If you spend 70k on a battery and then think you're getting one over on the power company by giving them 100 kWh of storage for the price of the cost difference on their daytime and nighttime rate, the power company is laughing all the way to the bank.