This poor woman’s alternative to on-demand domestic water heaters worked well for me when I was a stay-at-home mom with a young child. Simply install (or have an electrician install) an ordinary flip switch on your electric water heater. Buy and install an insulating blanket or two, and insulate any pipes that run through unheated spaces in your home.
After morning showers and other hot water use, turn the water heater off. There will be enough water in the tank to handle odd wash jobs during the day. Turn the heater back on in the evening to handle baths, dishwashing, etc. Then turn it off again before bed. If you install a timer on the switch, you can have the system turn itself on about an hour before you wake up in the morning. Otherwise, expect it to take about 30 minutes or so to heat up for morning showers, depending on the ambient temperature. You can cut your costs for domestic hot water in half with this simple solution.