Electronic thermostats offer considerably more control than electromechanical models, and their electronic sensing element is more responsive to temperature changes than bi-metal sensors.
A programmable electronic model allows you to set room temperature so that, in winter, your home’s temperature can dip down to a fairly low temperature—say, 60 degrees—after you’ve gone to bed and then rise to a comfortable 70 degrees when you get up in the morning. Or, if no one is home during the day, you can set it so the house cools down when you leave for work and returns to a comfortable temperature by the time you arrive home. Then, on the weekend, it can change to an entirely different schedule.
Using a programmable thermostat, you can eliminate considerable wasted energy. As a rule of thumb, every degree you turn down a thermostat will save 3 percent of energy costs over a 24-hour period. In other words, if you turn down the temperature from 70 to 61 degrees for an eight-hour period every night, you can save about 9 percent. Reducing daytime usage similarly can double your savings.