From WoWWiki
Lightning Overload is a passive talent that gives your Lightning Bolt and Chain Lightning spells {4/8/12/16/20}% chance to cast a second, similar spell on the same target with no cost. It causes half damage and no threat.
| Rank | Chance to cast
|
| 1 | 4%
|
| 2 | 8%
|
| 3 | 12%
|
| 4 | 16%
|
| 5 | 20%
|
Notes
- Spells cast due to this talent behave completely equal to their base spells.
- The net effect of this talent (maxed) is a 10% average damage increase for the lightning spells. (.5 damage * .2 chance = .1)
Past changes
- In Patch 2.3, chance of second no mana cost, half damage spell increased to {4/8/12/16/20}% with no additional threat. Prior to that the chance was {1/2/3/4/5}%, but spell's damage was not halved.