I don't have a nights and weekends promotion, or anything like that. Straight linear pricing.
I am doing it for environmental reasons. If I come home and plug in at 5 pm, and start charging, I am adding to the peak load in the afternoon in Houston. This means my EV charging load is added to the "pile" and drive up usage, which may result in an inefficient "peaker" plant that costs more to run coming online. If I instead charge the car at 1am, its in the "dead zone", when the wind power is really rolling, but nobody is using electricity. If the demand is low and the wind power produced is high, its a better chance that my power may actually be produced further west and shipped east.
Giant disclaimer: I DO know that my electricity usage as a single, inconsequential customer makes no real difference, but I feel that it makes my footprint smaller. I also don't like the idea that perhaps my car is coal powered, if I charge it at 5pm, instead of 3am. I also run my pool pump as much as possible at night versus the day. I load shift as much as is permissible.