Whats the percentage of energy that solar panels save?

Depends how large your solar panels are, and how sunny the climate is that you live in. Some very few extreme "green" houses dont even need to be part of the power grid. Most solar powered houses however don't store electricity. They send power to the power grid, and the electric company will calculate how much energy you use and how much you are giving them. If u give as much energy as you use, then your electricity bill will be zero dollars. If you give more than you use, then your power provider will usually pay you for the power your solar panels put into the grid.