I don't have smart washers, but I did build a smart ESP32-based [0] zigbee numerical display. Then I use Home Assistant to send the current electricity price to that display when the price changes, and send a notification to all users' phones when electricity is cheap (< 0.05€/kWh) or expensive (> 0.15€/kWh). This helps me plan my laundry and dish washing, which are the only energy intensive appliances I have. I also try to avoid cooking complex meals in the stove+oven.

[0] https://www.aliexpress.com/item/1005010546076391.html