What is resource usage based on in Fallout Shelter?

In Fallout: Shelter, managing the three available resources (Power, Food, Water) is an important mechanic. However, I'm not quite sure what determines the usage of these resources.

For food and water, I would expect it to be based on the amount of dwellers in the entire vault. However, it doesn't sound completely unreasonable that the function of some rooms may increase water usage.

What is food and water consumption based on?

Power ought to be tied to the production that goes on in the vault. But it isn't clear if empty rooms use power at the same rate as rooms being used (or at all). If so, the advice commonly given to not get too many dwellers too quickly could also hold true for rooms. Also, elevators may or may not use power.

How is power usage determined?

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 actually lists production and consumption rate totals for the resources.

Watching these closely as I built a vault from scratch, checking after each added room and during certain conditions I found the following,

Each dweller costs 0.36 food and water per minute. Children and adults cost the same. Explorers do not consume food and water.

Single rooms cost 0.52, double rooms cost 1.08 (+0.56) triple rooms cost 1.70 (+0.62)

Shut down rooms (like when at low power), elevators, and the vault door cost nothing.

I have yet to complete figuring out upgraded rooms. I also haven't checked advanced rooms, only the basic ones so far, quarters, diner, water, generator, elevators, and vault door. Once I complete advanced rooms and upgrades on the pc, I'll compare to my phone vaults for accuracy.

version 1.7.2 on pc Note, I did find that the listed rates occasionally vary by a point. I suspect this to be a floating point rounding error.