One of the things that Germans get a bit fanatical about (I hate calling it an obsession).....is electricity consumption, the attempt to use as little as possible.
For an American, it's one of the twenty-odd things that you notice the first month after you arrive and get to know Germans.
I noticed today out of N-TV....an article that looked at the general consumption in a one-person and two-person house.
In a one-person house....1,300 Kilowatt hours (kWh) is the low average for a year (does not include hot water heating). Mid-range goes to 2,000 to 3,000.....and high is 4,000 kWh.
In a two-person house.....2,100 kWh is the low average for a year, with 3,000 to 3,600 as medium and more than 4400 kWh noted as the high side.
The going rate (generally) is around.30 cents per kWh, so you can figure a young guy (single person apartment)...is spending near 390 Euro a year on electricity. At the high end for a single-person? 1,200 Euro a year.
All of this drives people to be fanatical about consumption.
For example, there are info sheets on electrical devices like freezers, coffee makers, and washers now....which tell you the average consumption rate and give it a grade. Germans actually read the sheets and make comparisons.
I sat and watched a TV info piece last year....some older German couple who had this 1988 freezer in the basement.....still operational and you could tell that the old guy really didn't have a desire to replace the freezer. The electrical expert came in....gave the big test deal, and then announced that the guy was paying near four-times the yearly cost of a more modern freezer. If he'd go out and buy a new freezer, it would have paid him back for the cost in just four years.
So if some German associate acts compulsive about turning things off or using dim lights...there's a logical reason for that behavior.