Do people have their own household generators running on natural gas or something?
No. That's really rare. I'd guess there are more generators in US homes (percentage wise I mean).
I could understand that power for heating could mostly come from gas, but presumably that is only needed in the winter?
Well, warm water is often supplied by oil or gas.
( Does Germany even have winter? I think Fahrenheit (the guy who invented the temperature scale) was German and he seemed to think that 0F was as cold as you could get, so I guess they don't have a real winter there.)
I guess that depend on what you consider "real winter".
Here are some numbers: http://de.wikipedia.org/wiki/Z...
The coldest month for last winter was January 2014 with an average of 2.1 degrees Celsius. 2013 it was February with -0.7 degrees C.
Coldest month since 1761 apparently was December 1788 with an average of -9.8 degrees Celsius followed by Feb. 1929 and Feb. 1959 with -9.6 degrees Celsius for both.