Power Efficiency linearly affects the cost of Warframe abilities. Positive Power Efficiency indicates a reduction of ability cost while negative Power Efficiency indicates an increase in ability cost.
- Ability Cost = Base Ability Cost × (1 − Power Efficiency)
Blind Rage also affects ability costs, but it increases them linearly.
- Blind Rage (-5% - Rank 0) / (-55% - Rank 10)
- Fleeting Expertise (+10% - Rank 0) / (+60% - Rank 5)
- Streamline (+5% - Rank 0) / (+30% - Rank 5)
Alternate helmets also reduce (or increase) ability costs linearly based on the percentage shown on the mod card. The following helmets affect Power Efficiency:
- Chorus Banshee Helmet (+10%)
- Essence Loki Helmet (+15%)
- Meridian Trinity Helmet (-5%)
- Scorpion Ash Helmet (-5%)
- Vespa Nyx Helmet (+15%)
Energy Bar RoundingEdit
The in-game energy bar display is rounded down, but the costs of the abilities are not. This results in the discrepancies in the apparent cost of abilities with Power Efficiency mods. For example, an ability with 25 energy base cost will cost 17.5 energy with maxed Streamline (+30%). If this ability is used multiple times in a row, it will appear to cost 18 energy, then 17 energy, then 18 energy, then 17 energy and so on. Energy Siphon can also change the apparent cost of abilities because it does not add a whole number to your energy.
Power Efficiency mods and alternate helmets stack according to the below formula:
- Ability Cost = Base Ability Cost × (1 − Streamline − Fleeting Expertise − Blind Rage − Helmet)
In other words, Streamline, Fleeting Expertise, Blind Rage and alternate helmets stack additively. Stacking with Meridian and Scorpion does not appear to follow this formula; this suggests stacking is different when you have a helmet that reduces Power Efficiency. Further testing and calculations are required.
Power Efficiency maxes out at 75% as of Update 10.3.0 which introduced new Corrupted Mods. This means that stacking bonuses over this wastes mod capacity. Currently, you can reduce 25 energy abilities to 6.25 energy, a 50 energy abilities to 12.5 energy, 75 energy abilities to 18.75 energy and 100 energy abilities to 25 energy. See Maximization for more information on maximum stats.
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