Hi, could someone please explain the difference between HPS lights used in the US vs the EU? I was told that the lamps are considerably different in arc voltage.

From what I can tell, the North American low wattage high pressure sodium lamps from 35w S76 to 150w S55 have an arc voltage drop of roughly 55v while European 35w to 150w high pressure sodium lamps have an arc voltage drop between 85v and 100v except for the 35w lamps made by Tungsram. In addition, the 250w and 400w high pressure sodium lamps are universally interchangeable all across the world all with an arc voltage drop of about 100v. Lastly, the North American 1000w S52 high pressure sodium lamp has an arc voltage drop of 250v while most European 1000w high pressure sodium lamps have an arc voltage drop of roughly 110v. It is also good to note that North American 150w S56 high pressure sodium lamps are interchangeable with European 150w high pressure sodium lamps.

Since European low wattage high pressure sodium lamps have an identical arc voltage drop and current that North American low wattage pulse start metal halide lamps have, you should have no problems with running European low wattage high pressure sodium lamps on same wattage North American low wattage pulse start metal halide ballasts if they are HX autotransformer ballasts or series choke ballasts.