Also when you "open the door", because heat rises, the oven only looses 15 degrees C at most.
Siemens actually do some really nice appliances though.
As I'm sure you might know Siemens and Bosch have a joint venture appliance manufactuer, BSH - Bosch Und Siemens Hausgerate GMBH.
It seems that Siemens badged products are marketed as being more high end though.
They also do:
Gaggenau (very high end built-in stuff mostly)
NEFF (similar - high end built in)
Thermador (US brand)
Constructa (German brand)
Viva
and ufesa (Spanish small appliance maker)
75.4% of all of their sales are in Western Europe though.
Despite Bosch in the USA, only 6.6% of their sales go to North America.
Sales : €7.34 Billion / Year (US$ 9.36 billion)
35,500 employees.
Not as huge as Electrolux or Whirlpool, but still an enormous company.