Your power, or "Pw", is the amount of magical energy you have. For example:
Dlvl:3 $:43 HP:68(68) Pw:13(18) AC:-3 Xp:8/1295 T:2358
The above status line shows a character whose current power is 13 and maximum power is 18.
Uses of energy
The main use of energy is to cast spells. You need 5 times the spell's level of energy to cast a spell. When carrying the Amulet of Yendor, there is an additional random cost. This cost applies only to spellcasting, not to any other expenditure of energy. See spellcasting cost for more details.
Certain #monster commands require energy. The breath weapons of dragons, iron golems, winter wolves and hell hounds all cost 15 energy . Summoning help as a werecreature , and emitting psychic blasts as a mind flayer  both cost 10 energy.
You normally regain energy slowly over time, unless your encumbrance is Stressed or worse, which blocks normal energy regeneration. Having the Eye of the Aethiopica allows you to regain energy rapidly, even when stressed.
Quaffing a non-cursed potion of gain energy increases your current and maximum energy; a cursed potion decreases them.
Reading any scroll of charging while confused recharges your energy to its maximum. If it was already maximum, you gain 5d4 total energy instead. In 3.6.0 or later cursed scroll will reduce energy to 0 without altering the maximum “You feel discharged.”
Eating a newt corpse sometimes increases energy by 1 to 3 points. If this would put you over the maximum, your maximum energy might also increase by 1.
Attacking a spellcasting monster with Magicbane has a chance of cancelling it and increasing your current and maximum energy by 1 (“You absorb magical energy!”). Only the cancellation from Magicbane can absorb energy. This effect happens every time the cancellation attack hits, not just the first time, when the monster is actually cancelled.
Lying with a foocubus may increase or decrease your energy.
The polyself bug can be exploited to increase your maximum energy exponentially.
The amount of energy regenerated each time is between 1 and , which for most characters means 1d2 or 1d3.
Number of turns between regenerating energy:
Level gain and starting energy
When you gain a level, both your current and maximum energy are increased based on various factors:
Your role modifier depends on whether your experience level (before the level gain) is lower than a certain cutoff which varies between roles. If it is, apply the "low-XL" modifier; else use the "high-XL" modifier.
The result of this is then multiplied with your energy modifier, which depends on your role, and rounded down.
The final result will be added to both your current and maximum energy.
For a newly created character neither energy modifier nor Wisdom matters: certain magically inclined roles start with a few energy points at random, while others only get one point; all races except Dwarves also get a bonus point or two. See the table below for precise numbers.
Self-teleport costs 30 points of power.
The energy regeration frequency formula is changed to turns if you are a Wizard, and every for all other roles.
- teleport.c in NetHack 3.4.3, line 517
- polyself.c in NetHack 3.4.3, line 748
- polyself.c in NetHack 3.4.3, line 910
- polyself.c in NetHack 3.4.3, line 1075
- read.c in NetHack 3.4.3, line 1056
- trap.c in NetHack 3.4.3, line 1058
- artifact.c in NetHack 3.4.3, line 844
- allmain.c in NetHack 3.4.3, line 211
- exper.c in NetHack 3.4.3, line 195
- exper.c in NetHack 3.4.3, line 196: The function also considers a race modifier, but this is 0 for all races.
- exper.c in NetHack 3.4.3, line 197: This also considers a role minimum, but this is 0 for all roles.
- exper.c in NetHack 3.4.3, line 201
- newpw in exper.c
- enermod in exper.c
- SLASH'EM_0.0.7E7F2/teleport.c, line 790