Okay, I did a lot of tests: placed generator inside and outside a building, the same for electrical devices, compared gas consumption with quantities of electrical devices and other. The conclusions are as follows:
1. It doesn't matter where generator is, it's range is the only thing that matters. This range is 20 tiles (image below--resolution is 1440x1080, max zoom out, granite tiles are the last tiles with electricity (checked with equipped tv)) and 5 floors (the one it is placed at, two down and two up). The power consumption is the same on all floors. It also seem that condition does not affect the consumption.
2. Electrical devices only consume electricity when placed under a roof (floor) (as in, directly under one, not in general (if you make a single hole in your roof under a certain device, only this device wont consume electricity)) (whether pre-existing or self-constructed roof) (walls do not matter). That's why when I first checked with dozens of devices the consumption was minimal (11% per day). This is most likely a bug, as it makes no sense--after all--those devices still work. Basically it's a big "cheese".
3. Now for the consumption itself.
First: lamps, switches and other light sources do not consume electricity, just as you sad.
Second: consumption of ovens and microwaves (and cooking devices in general (my guess)) has a pattern, and it is as such:
- 1 microwave: 11% / day
- 2 m-w: 11% / day
- 3 m-w: 11% / day
- 4 m-w: 11% / day
- 5 m-w: 23% / day
- 6 m-w: 23% / day
- 7 m-w: 23% / day
- 8 m-w: 34% / day
- 9 m-w: 34% / day
- 10 m-w: 34% / day
- 11 m-w: 34% / day
- 12 m-w: 46% / day
You can see a pattern: 4|3|4...and as follows. (Drying machine has the same consumption.)
Third: the same goes for all types of freezing devices (fridge, mini fridge and popsicle fridge). The pattern is as such:
- 1 fridge: 11% / day
- 2 f-g: 11% / day
- 3 f-g: 23% / day
- 4 f-g: 34% / day
- 5 f-g: 34% / day
- 6 f-g: 46% / day
- 7 f-g: 57% / day
- 8 f-g: 57% / day
- 9 f-g: 69% / day
- 10 f-g: 80% / day
- 11 f-g: 80% / day
The pattern is: 2|1|2|1|2...and as follows. (Washing machine has the same consumption.)
Fourth: the gas consumption "tick" happens every hour, regardless of consumption. (Ha-ha, this got me thinking: you could probably fill every tile on five floors with electrical devices, but because the tick happen every hour strictly, you will run out of gas only after an hour, even through your real consumption would be way above that.)
I also tried looking at consumption of fridges and microwaves combined, and this is what I got:
- 2 f-g + 2 m-w: 23% / day (as 3 fridges)
- 2 f-g + 4 m-w: 34% / day (as 4 fridges)
- 2 f-g + 8 m-w: 46% / day (as 6 fridges)
Basically, every two cooking devices are worth as much as one fridge in power consumption increase.
And this is it, I think. I probably covered everything, but if you have questions or suggestions, go at it. Also I used "NecroForge" and "CheatMenu" to help with the tests (spawning items, god mode, free building, instant action, time skip, time warp, teleportation). Also, those cheats did not affect the tests--I checked.
Man, that was informative.