There is no water shortage, there is an energy shortage. You can easily desalinate as much water as you want, it costs about $0.002 per gallon, while heating a gallon of water is 10x that.
Desal is 3.8 kilowatt-hours per thousand gallons while heating water 70 F to 120 F (reasonable minimum range) is 122 kWh per thousand gallons. You're absolutely right, this is a case where it makes no sense to use energy to save water.
