Not sure if this has been scientifically studied but I’ve noticed a couple situations where continuous heat can be avoided.
My mom’s way of cooking corn on the cob: bring a pot of water to boil, lid off with two wooden spoons resting on the top to prevent boiling over. She keeps the heat continously quite high for what, ~30—40 min? Seems wasteful because with the lid off the pot is evaporative cooling the whole time so more heat is needed to offset the cooling. I just tried it this way: bring to boil with lid on. Shut the burner off as soon as it boils. The corn continues cooking as the water temp drops. I could probably improve on that even more by using a pressure cooker. (I’m stalling on buying one because I boycott InstantPot due to the fact that they have a closed source phone app exclusively in Google Playstore; it’s optional but InstantPot buyers are still financing that. I should probably get a 2nd hand manual pressure cooker).
Hydrating dried beans: soak overnight (which I skip because it seems to make little progress). So I do the “quick soak” – bring to boil with lid on, turn off right away, and let them sit ½ the day in warm water. Pressure cooking speeds up the 2nd stage cooking for sure (I’ve tested with other people’s pressure cookers). Since I don’t have a pressure cooker, I end up doing the quick soak method ~3 or 4 times throughout the day… which just means bring to a boil then shut off. Anecdotally this seems to reduce the time needed in the final phase of cooking.
Am I going OCD on this? This all might be a drop in the ocean… cooking is not a significant portion of energy consumption. But maybe notable in the summer when cooling systems have to work against the kitchen heat. Which is one reason I like the electronic pressure cookers: I can set the pressure cooker outside.
FYI, new manual pressure cookers are still a thing. A recently-made used one is fine, and obviously best in terms of minimizing cost and manufacturing and such, but it’s better to resort to buying new than to get a really old one with a less-safe design.
Electronic pressure cookers made by companies other than Instant Pot are a thing too, by the way.
Another way to accomplish that would be to get a portable induction burner and set a manual pressure cooker on top of it.
I love the convenience of the electric ones and the programmability. But tech ethics makes them a minefield. One advantage of the manual ones is they can do much higher pressures. The so while the electric ones give more control by giving programs and timers, they give less control over the pressure level. IIRC the InstantPot just has low and high. And “high” pressure is still relatively low.
Ideally we need a FOSS pressure cooker.