Modifies the Energy cost of Warframe abilities. The minimum Energy cost is 1/4 of the Base value.
—In-game Description
Ability Efficiency linearly affects the energy cost of Warframeabilities. All Warframes have a base Ability Efficiency of 100%; Ability Efficiency over 100% indicates a reduction of ability cost while Ability Efficiency below 100% indicates an increase in ability cost. The Arsenal will not display an Ability Efficiency above 175% because abilities cannot consume less than 25% of their base costs.
Mechanics[]
When accounting for ability efficiency, ability energy costs can be calculated:
Channeled abilities drain energy at a specified rate. Ability Efficiency affects the energy drained at each tick as expected, but because Ability Duration affects the amount of time between these ticks, the formula for effective Ability Efficiency for channeled abilities is as follows:
In the case of Ability Duration under 100%, Ability Efficiency above 175% is also taken into account, even though not depicted in the Upgrade-Menu. The final drain still cannot go below 25% of its base value. (See the graph on the right for examples.)
The in-game energy bar display is rounded down to the nearest whole number, but the costs of the abilities are not. This results in the discrepancies in the apparent cost of abilities with Ability 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 Drain for Toggled Abilities[]
Some abilities are toggled on and last until the user turns them off or runs out of energy, such as Hildryn's Haven or Chroma's Spectral Scream. Energy drain for these toggled abilities depends on both Ability Efficiency as well as Ability Duration. See the related section for a full explanation.
Other Behavior[]
Some Warframe abilities do not cost energy to cast, thus ability efficiency has a unique effect on these abilities:
Garuda slashes herself with her talons as she spins into the air, sacrificing up to 50% of her maximum Health and restoring up to 18% / 22% / 30% / 35% of her maximum Energy capacity. Garuda cannot reduce her health below 2 health points using Bloodletting.
Health cost is 50% of Garuda's maximum HP, including mods.
Energy gain is the listed % of her maximum energy, including mods.
Energy gain is affected by Ability Efficiency. For example, 160% Efficiency results in 87.5% Energy gain, while 175% Efficiency results in a 140% gain. This follows the formula:
Total Energy Gain = Base Energy Gain ÷ (2 - Ability Efficiency).
Bloodletting can be cast if Garuda has less than 50% of her maximum HP remaining, but will only restore energy proportionate to the amount of HP sacrificed. For example, if she has 25% of her health left (or 50% of 50%) when Bloodletting, the energy gain will be halved.
Percentage of health deducted is not affected by mods.
High enough armor, Energy, and the use of Quick Thinking and/or Gladiator Finesse can effectively make this ability put the Death's Gate passive at a constant max state with a small failsafe with energy. Additionally, Health Conversion charges cannot be lost, as your HP cannot reduce below 2HP, so you can stack around 90% damage reduction from armour with the efficiency reduction from a max rank Quick Thinking.
This ability gains no benefits from increasing your max HP. Having lower max HP lets you use flat HP regeneration such as health orbs or Oberon's Renewal to generate more energy more quickly.
Synergizes with Blood Altar's continuous healing to give Garuda a near infinite supply of energy.
Bloodletting is a powerful ability to combine with Helminth-infused abilities that constantly drain energy, the most notable being Sevagoth's Gloom as it provides Garuda with another self-healing ability besides Blood Altar to constantly regenerate her energy reserves.
Transmutation Probe Launch a probe that converts Health and Energy Orbs into Universal Orbs that provide both, and ammo pickups into Universal Ammo Pickups. The probe shocks enemies in close proximity. Each electrocuted foe reduces other ability cooldowns by one and a half second. Hold to imbue the next ability cast with Electricity damage.
Efficiency:1.5 s (Cooldown Reduction per enemy shocked)
Misc:15 m/s (probe speed) 3 s (probe duration) Electricity and imbued elemental status proc per second 0.5 s (halt delay) 25 HP/EP (Universal Orb restore) 10 % (Universal Ammo restore)
Lavos launches an advanced alchemical apparatus toward the direction of the aiming reticle. The Transmutation Probe is an invulnerable floating device that travels at a speed of 15 meters per second, lasting for 3 seconds, as it emits a field of electrical currents spanning a 3 / 4 / 5 / 6 meter radius. Enemies within the electric field receive 100 / 150 / 200 / 250Electricity and 100 / 150 / 200 / 250 Imbued Elemental damage and status effects per second; for each enemy electrocuted, 1.5 seconds is removed from the active cooldowns on Lavos' other abilities. Press the ability key again (default 3 ) after the ability has been active for at least 0.5 seconds, to hold the probe's position at its current location. Casting Transmutation Probe triggers a cooldown of 10 seconds when the active probe expires, before a new probe can be launched.
Probe speed, probe duration, status procs per second, halt delay, and cooldown are not affected by mods.
Electric field does not require enemies to be in direct line of sight to apply damage and status effects.
The probe's duration timer is shown on the ability icon and must expire before the ability cooldown begins.
Therefore, Transmutation Probe cannot reduce its own cooldown timer.
Each enemy shocked may only reduce Lavos' other active ability cooldowns once per probe, not repeatedly while they stay in the field.
Although appearing as a floating object, the probe is affected by gravity and will drift down to the lowest available horizontal surface as it travels.
The probe collides with solid obstacles in the environment, stopping its movement prematurely.
Halting the probe by pressing the ability key again will stop the probe's movement permanently until it expires.
Standard Pickups on the ground that pass through the probe's field, including Health Orbs, Energy Orbs, and Ammo Packs, are transmuted into special Universal variants; Universal Orb provides 25Health and Energy points, while Universal Ammo Pack replenishes 10% of a weapon's ammo reserves for all equipped weapons.
Universal pickup restore values are not affected by mods.
Hold down the ability key (default 3 ) to add Electricity damage to Lavos' mixing vial at no cost, as the Imbued Elemental damage type for his next ability cast.
Transmutation Probe reduces all active cooldowns on Lavos' other abilities, including Helminth Subsumed abilities, for each enemy it electrocuted. If enemies were electrocuted while Lavos' other abilities are in use, but their cooldowns have not yet begun, the cooldown reduction is carried over to the cooldowns.
Electricity status effects inflicted on enemies by Transmutation Probe enhance Catalyze's damage.
Can be cast and halted while moving or in midair. The probe will descend in a diagonal glide to the ground.
Casting Transmutation Probe is an upper-body animation that allows movement while restricting other actions. Holding the probe's position does not play an animation on Lavos.
Nullifier Crewman and Isolator Bursa bubbles are considered solid objects that block Transmutation Probe from traveling through them.
Lavos visually summons the Transmutation Probe from his right hand as he throws the probe forward. The probe remains in perpetual motion rotating its upper half counterclockwise and lower half clockwise, while emitting two jets of gas for propulsion. Electrical currents forming the transmutation field encircle the probe in a similar pattern to electrons orbiting an atom. While in motion, the probe pushes a large spiraling energy force.
When a different element is imbued, the electrical currents adopt different appearances and energy particles representing the additional elemental damage type.
Transmutation Probe, gas jets, electrical currents, elemental particles, and energy force are affected by Lavos' Appearance colors.
Universal Orb visually appears as a pulsating, rippling orb with a diluted blue outer layer enveloping a red inner core. Universal Ammo Pack shares the same model as those produced by Protea's Dispensary.
Arcane Helmets also reduce (or increase) ability costs linearly based on the percentage shown on the helmet. The following helmets affect Ability Efficiency:
Hildryn's 
Haven or 
Chroma's 
Spectral Scream. Energy drain for these toggled abilities depends on both Ability Efficiency as well as Ability Duration. See the related section for a full explanation.
Electricity damage.
Streamline, 
Pax Bolt, and the positive Ability Efficiency Arcane Helmets stack additively. Stacking with Trinity Meridian Helmet or Ash Scorpion Helmet does not appear to follow this formula; this suggests stacking is different when you have a helmet that reduces Ability Efficiency.
