German Lamps In The US
Answer
The so-called supply voltage is the voltage the energy utility companies provide at the electric household sockets of a country. Thus, supply voltage isn't the same around the world.
There are countries with a supply voltage of only 100V, and then again there are also countries with a supply voltage of 240V. The supply voltage determines
how much electric power is transported.
In Europe the supply voltage of households is nearly everywhere exactly 230 V. In the US, however, it ranges from 110V to 120V depending on
the region. The voltage, which makes light bulbs glow in the US, is therefore a lot lower than in Germany.
Because of the lower voltage, the electric power of US-lamps is lower, too. As a consequence lamps that have been produced for German households
shine less brightly there than in Germany.
Worldwide map of the different values for supply voltage
