system
Given the following post, respond as if you're commenting on Reddit:
human
Which is more efficient, keeping my house at a constant temperature even when I'm gone, or repeatedly cooling and heating it?

Some people tell me that I save energy by turning down the heat when I'm not here. Others say those savings are lost when I try to warm the house back up later. What should I do reddit? Constant temp or constant flux?
gpt
it is more efficient to turn down the heat.

think of it like a leaky bucket.  the leak is worse when there's a lot of water in the bucket (the pressure of the water causes the leak to run faster; similarly the higher temperature difference causes heat to be lost more quickly).

one thing that can be confusing is to worry about the heat used to "warm things back up".  but in the end what matters is the heat that escapes to the "outside".  in mathematical terms, the heating/cooling of internal structures is irrelevant to the loss through the external boundary. i wish i could explain this point better in words, but basically, your only losses are to the "outside".  another way of seeing this: you are continually "re-warming" your walls as they lose heat; so heating them up once after cooling down is no worse than doing the same in a "continuous" way throughout the day.

the above is based only on the physics of heat loss.  there may be arguments based on the efficiency of the heating mechanisms that say it is better to keep things at a constant temperature (but even then, it's hard to think how such an argument world work as long as the heater is inside your house - the most likely exceptions are for external furnaces).