Avoiding large fluctuations in temperature

This is true. I've seen some calculations on energy needed to maintain for 8 hours vs to reheat a large differential.

Efficiency aside, both summer and winter I lower the temperature at bed time for comfort.

Another mistake some people make is setting the thermostat to an extreme number. If they want to go from 65 to 70, they set the thermostat to 80 thinking is will heat up faster. No matter the setting, the heat output (or cooling) is determined by the capacity of the unit.

With a heat pump system, or maybe a variable output furnace, it could be true. With a single output furnace, it is nonsense. The furnace cannot "work harder". It has 1 level it works at, and only the time changes. And clearly, the more the house temp drops as it cools, the slower heat energy is lost, which makes a big difference. The total time the furnace runs will be less. It will just run a bit longer in the morning to heat the air, and cycle a little more early in the day until the structure warms up.

I was surprised, but I found that a furnace DOES heat up faster when the thermostat is set higher (at least in one particular case). It seems to be because of something in the thermostat called the "heat anticipator" that turns the furnace off sooner.

It was set at 70, but off and the temperature was down to around 50 when turned on. The furnace ran awhile and turned off around 62. Consecutive cycles would increase the temperature more.

The heater, no matter the fuel, has a maximum capacity of output. Some may cycle based on internal sensors that keep the system from overheating. In a water system, if the heat is not carried off fast enough it may cycle so the heat exchanger does not overheat.

The heat anticipator does a similar function to avoid the temperature going above set point. Even though the burner stops, heat from the surrounding firebox and exchanger will give off some heat so the T-stat shuts it off early. Accuracy depends on many factors.

Beginning the heating cycle *sooner* does not necessarily equate to heating *faster*. My Honeywell t-stat has the Heat Anticipator feature. When programmed to begin a heating cycle for, say, 8:00AM, the t-stat starts the furnace at perhaps 7:30 so that the desired temperature is obtained by 8:00. My furnace has only two operating modes: on or off. When it's on, it has a fixed output. It does not heat the house any faster; it simply begins the heating cycle sooner.

SOME 2 stage units will kick up to high if the difference between ambient and set is more than X degrees - so may heat faster. My furnace starts at 3500 BTU, and kicks up to 50000 or 52000 after 6 minutes of running?. Mine does not have external air temp input.

Heat pumps often have strip heaters that come on if the set temperature is more than about 2 deg higher. So it will heat the house quicker at the expense of much more electricity.

Definitely. Any time I see "work harder" used, I'm suspicous that the writer is blowing smoke.

Right.

Right.