Fallout – Dwellers not consuming resources

Just got a loading screen tip in the game (the wording may not be exactly the same, but the general meaning should):

Dwellers run on food and water. Rooms run on Power.

This is certainly an official source, although not a very in-depth explanation. From this, one could draw the conclusion that rooms consume power regardless of occupancy, and only dwellers use water, even if this isn't explicitly stated.

To further investigate the details (unless some other source is available), I suppose someone will have to do some science.

Edit: It appears the good folks over at /r/foshelter/ have done quite a bit of science.

Some key points relating to the resource consumption (not absolute facts, but probably close to the truth):

• Food/Water consumption is 21/hour per dweller in the vault (so explorers don't count). This means a L3 full-size Nuka-Cola plant can supply 100 people with food and water.
• Power consumption is a bit more complex, and isn't fully explored yet, but it seems to change with the level of rooms. Still unclear if elevators and other things consume power. For now though, don't build more/larger rooms than you need if power is an issue.

There are a lot of other interesting points made in the thread linked above, so I really recommend checking it out. More detailed information is available here. If they keep the work up, this may be the go-to resource for data on the game.

The game has 2 different running in background behaviours:

• The game's wiki specifies that the resources will be consumed only for a little while after the game is no longer in use (game sent to background, phone not used etc). This is due to the fact that the resources require a lot of management and you would have to check/play the game every few minutes, half an hour at most, before your dwellers would start dying, get irradiated, etc
• Other activities that require a long time will still be in play (or generated once you open the game again, based on how long actually took since you last stopped playing - in normal hours) ... these activities are: wasteland exploration and returning, training, pregnancy, baby growing up, radio and creating resources
• You will also never be attacked by raiders, deathclaw or molerats while the game is on background.

As an example: A baby requires 3 hours in order to grow up and become an adult. When you open the game again, the game will check if 3 hours have passed since the baby was born to determine whether to make that baby an adult.

Warning: Players tried to fool the game by changing the timer, clock... be aware that this can cause lots of bugs, malfunctions, freezes, crashes etc

TL/DR: Yes, resources will be consumed only when you play the game or for a short while after you stop playing the game.