iab: you understand correctly. Like I said, in reality, there are many variables. Insulation for example. In a very drafty house, it may take more energy to maintain temperature than to just let it drop and boost it up a few hours later. In a very well-insulated house, where the heat loss is very low, it takes very little energy to maintain the temperature. Therefore, in a well-insulated house, the time period for an energy saving setback is much greater than in a drafty house.
In properly constructed new houses, the energy loss is ridiculously low. It’s a shame that McMansions are so ugly, because we are truly living in the best of times for construction technology…
We also have a much better understanding of indoor air quality and how to maintain comfortable humidity and temperature. It’s amazing!