That would be a dumb home then. A smart home would be properly insulated and a lot more passive, it wouldn't leak as much heat and wouldn't be cold when you get home. All without "smart" tech or burning extra fossil fuel.
Did you run the numbers on savings with insulation vs using "smart" tech?
Usually, it's only a matter of time before insulation pays for itself, the time being roughly a decade. Still, people would rather limp along rather than fix it up.
Grandma tech: keep rolls of sugar cookie dough in the freezer, and bake 'em when you get home. An excuse to hang out by the oven, and then you have cookies.
Curious if that saves any significant energy, if you visit home regularly. The same with summertime AC. I believe that allowing a properly insulated room to get hot/cold and then reheating/recooling it takes the same work, because half a day is barely enough for it to get equilibrium with the environment. For a week probably yes, but then again you don’t want your home to cross a freezing point too often. Am I right or naive here?
You are half-way right (or half-way naive, it depends on points of view).
Generally speaking (but it depends greatly on the specific home thermal properties and on the kind of heating or AC you have) it is usually less energy intensive to keep in winter your home at a certain temperature (lower than normal but not too lower) than to switch off completely heating and then when you get home boost to the wanted temperature.
Many years ago I knew someone (an electrical engineer by trade) that modified a standard/ubiquitous Panasonic telephone answering machine connecting it to his home thermostat, he used the code to hear messages to switch the heat on.
You don't need the internet, nowadays the equivalent would most probably be something like :
A smart system would learn your patterns and eventually be able to predict your arrival, setting a temperature that's further away from ambient and towards some target the more confident it is.
