If 65 days of the year you charge and 300 days you don't, it likely isn't cost effective.

Peak time is also during the daytime which means baseload power sources like Gas/Hydro/Nuclear/etc. are likely fulfilling demand at night just fine.

Most likely you are charging during winter and discharging during heat waves in the summer which may not be a viable business model despite the large delta in energy prices.

At least that is my understanding, I'm not an expert. xD