Where is the generator in Pokemon HeartGold?

Answer 1

Go to Cerulean City. Leave it via the right path. You should now be on Route 9. Jump down, then travel right, following the yellow path, not going on the green area. Go up the stairs, and jump down. You should now be next to a female picnicker. Carry on going right. There should be some long grass, and some steps leading down to a river. Surf on the river, and go right then down. While on the river you will see a Pokemon Centre above. Continue going down. When the river turns left, you should see a building, which is the Power Point

Simpler Instructions

Go to Cerulean City. Go right untill you reach a river. Follow the river down untill you see a building (not the pokemon centre). That is the powerplant.