It tends to be tricky to do this without wasting a lot of power, most thermostat auto modes have a pretty wide spread of maximum and minimum temperature because

It tends to be tricky to do this without wasting a lot of power, most thermostat auto modes have a pretty wide spread of maximum and minimum temperature because otherwise you run the risk of oscillating between using energy to heat and using energy to remove the heat you've just added. It can be done care and tuning, but the average home HVAC setup is not designed or installed with care.