After baking “… I leave the oven door open so the heat can get out.”   I heard this when we were talking about thermostats and insulation and things one day at tea time.   ‘Twas said with a bit of smugness, and I caught the flavour of someone trying to pull an ecological trump card.

Nope.  Sorry.   Doesn’t matter.

Energy cannot be created or destroyed; it just moves around.   So, if you oven eventually cools off, the energy has gone somewhere.    Most ovens are surrounded by house, so the energy has nowhere to go but into your house.

Since it can’t be created or destroyed, the same amount will eventually flow into your house, no matter what you do.   So leaving the oven door open doesn’t matter in the long term.   (Though in the middle of a British winter, it feels rather nice for 15 minutes…)   It just controls how fast the heat gets into the kitchen.  You can have a lot of heat for a little while or a little heat for a long time.

* And, yes, I’m assuming that the heat doesn’t flow back out the electrical wires or the gas pipes.