There is no "normal" level. It depends on what Pokemon you are facing while training Pichu. If you are facing low level Pokemon and doing all the things that raise happiness (massages, etc) then Pichu will evolve at a lower level. If you go against the Elite 4 with a Lucky Egg and do the "start with Pichu then switch out" trick, Pichu will evolve at a much higher level. Just by going through the game, if I have a level 5 Pichu let's say, I would usually evolve it by level 25.