I've included the descriptions from the SRD of both the Power Attack feat and the nonlethal damage section of Combat.
I've seen other players using saps (in particular rogue sap masters) and fighters with merciful weapons doing power attack and non-lethal together. However, reading Power Attack to remind myself of the differences between PF and 3.5, it says the bonus damage does not apply to effects that do not hit point damage. And non-lethal damage says it is tracked separately from hit point which implies it is not hit point damage.
Doesn't that mean that you don't get the bonus damage of power attack when you deal nonlethal damage?
I was looking at playing a sap master myself in PFS, but I don't want to be a cheater by using Power Attack if it does not work together.
Thanks,
Eric
Power Attack (Combat)
Benefit: You can choose to take a –1 penalty on all melee attack rolls and combat maneuver checks to gain a +2 bonus on all melee damage rolls. This bonus to damage is increased by half (+50%) if you are making an attack with a two-handed weapon, a one handed weapon using two hands, or a primary natural weapon that adds 1-1/2 times your Strength modifier on damage rolls. This bonus to damage is halved (–50%) if you are making an attack with an off-hand weapon or secondary natural weapon.
When your base attack bonus reaches +4, and every 4 points thereafter, the penalty increases by –1 and the bonus to damage increases by +2.
You must choose to use this feat before making an attack roll, and its effects last until your next turn. The bonus damage does not apply to touch attacks or effects that do not deal hit point damage.
Nonlethal Damage
Nonlethal damage represents harm to a character that is not life-threatening. Unlike normal damage, nonlethal damage is healed quickly with rest.
Dealing Nonlethal Damage
Certain attacks deal nonlethal damage. Other effects, such as heat or being exhausted, also deal nonlethal damage. When you take nonlethal damage, keep a running total of how much you've accumulated. Do not deduct the nonlethal damage number from your current hit points. It is not "real" damage. Instead, when your nonlethal damage equals your current hit points, you're staggered (see below), and when it exceeds your current hit points, you fall unconscious.
Nonlethal Damage with a Weapon that Deals Lethal Damage
You can use a melee weapon that deals lethal damage to deal nonlethal damage instead, but you take a –4 penalty on your attack roll.
Lethal Damage with a Weapon that Deals Nonlethal Damage
You can use a weapon that deals nonlethal damage, including an unarmed strike, to deal lethal damage instead, but you take a –4 penalty on your attack roll