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What you'll need is an old pre-war F.C., a standardized Fusion Core. Your high-grade, long-term nuclear battery. Used by the military and some companies, way back when.Preston Garvey

The fusion core is a type of ammunition in Fallout 4.


Standardized fusion cores are a high-grade, long-term nuclear battery used for military and commercial applications before the Great War.[1] Used by civilians to power a multitude of devices, from automobiles,[2] to generators,[3] the military instead used them for warfare, supplying power armor and some Gatling laser models with energy. Standard core interfaces were developed across the board to allow for power armor frames to use cores salvaged from weapons or generators.[4] The fusion core also can be hooked up to certain melee weapons via jumper cables.[5]

Another benefit is that cores can be set to overload, for use as improvised explosives or to deny a power armor suit to the enemy by destroying it.[6]


Fusion cores are used to power and activate suits of power armor. Each core provides roughly 20 minutes real time (or approximately 10 hours game time) of power armor use when jogging (default pace). Actions based on Action Points (AP) usage, such as holding breath when using scoped weapons, sprinting, utilizing V.A.T.S., or jet pack modules causes the power to drain much faster, whereas walking consumes less power and remaining stationary drains none. While the Sole Survivor can utilize power armor without a fusion core, they will be unable to move at a pace greater than a slow walk (similar to being overencumbered) and actions requiring AP will be restricted.

Fusion core lifespan is represented as a percentage. Fusion core lifespan can be extended by 10% by collecting the Repair bobblehead, and by up to 100% by investing points in the Nuclear Physicist perk. Instead of increasing the maximum charge percentage, these will slow the rate at which the charge level drains.

The Gatling laser utilizes fusion cores as its ammunition, each core providing 500 shots. Nuclear Physicist can increase the number of shots per core up to 1000, but the magazine capacity will remain at 500. Also combining with the Repair bobblehead, the total amount of shots can be raised to 1100.

Fusion cores can also be ejected from power armor suits if one has the highest level Nuclear Physicist perk and no other explosive devices are currently equipped. Ejected cores land a short distance behind the user where they act as a sort of timed mine with a destructive force similar to that of a Fat Man's projectile. Note that contrary to the perk description, the cores cannot be actually thrown like regular grenades.

Fusion cores glow when they suffer critical damage and eventually erupt in a small but powerful nuclear detonation.

The core of a worn suit of power armor may be targeted using V.A.T.S. A successful hit will cause the core to suffer critical damage, causing a small nuclear explosion behind them, forcing the character wearing the power armor to exit it.

In addition to fixed locations below, fusion cores may also spawn in groups of four in certain ammo boxes across the Commonwealth. Cores can also be spawned in other container types by means of an eyebot pod, but only one at a time.

Weapons using this ammunition


Location Amount Description
Far Harbor (add-on) Acadia 2 On the bottom level of the interior of the observatory in a locked storage room. The storage room can be accessed by picking a Master-locked door or by hacking a Master-locked terminal.
Nuka-World (add-on) Angry Anaconda 1 In the fusion generator located beside the expert locked portable cabin.
ArcJet Systems 1 In the room where the Sole Survivor can restore power to the elevators.
Atlantic Offices in the Glowing Sea 1 Atop the roof.
Back Alley Bowling 1 On the second floor underneath a metal shelf in the hallway, behind the bar.
Boston Airport 1 Spawns in the cargo area after Reunions.
Boston mayoral shelter 1 In a room off the basketball court with a sign above it that reads "Restricted Area."
Cambridge Polymer Labs 1 In the office, accessed by either by picking the Master lock or successfully finishing the laboratory's research.
The Castle's tunnels 3 One can be received from the generator in the same room as the chemistry station. Two more can then be obtained from Sarge.
Nuka-World (add-on) Cola-cars arena 2 One can be found sitting in a locker next to the ammo crate on the opposite side of where the intercom can be found. Another in a generator can be found by going through the bathroom, in the same room and going through the destroyed wall in the corner.
Concord civic access 1 In a dark corner opposite the small drug cache that the mirelurk guards.
Far Harbor (add-on) Crashed boat 1 Southwest of the Harbor Grand Hotel on the shoreline there will be a crashed ship with containers arranged to the side of the boat with flames trailing behind it. On the bottom floor, there will be a fusion generator with the fusion core.
Erin Combes 1 Will give one for finding Ashes in the quest Here Kitty, Kitty as long as no speech checks were used when agreeing to find Ashes.
Factory 1 On a generator located in the western corner of the building.
Federal ration stockpile 2 One in a generator located behind the bunker to the northwest of the compound. Another is in the underground bunker. Once inside, take the first door on the right, then through two flooded rooms to a Novice-locked door. It is in the generator in the back of the locked room.
Nuka-World (add-on) Fizztop Grille 1 On the outside patio, on the nightstand at the right hand side of the bed.
Fort Hagen Command Center 1 In a generator room to the west.
Automatron (add-on) Fort Hagen satellite array Found from assorted Mechanist robots bodies.
Four Leaf fishpacking plant 3 Two inside (one of them behind a mag-lock door) and one on the roof of the building.
Far Harbor (add-on) Glowing Grove 1 On one of the tables.
Goodneighbor 4 Two of the cores can be obtained during or after the The Big Dig in any ending. One can be found in the generator on the left side of the first room one enters into after Sonya blasts the first dirt wall. Another generator holds one behind an expert-locked door when taking the righthand path after the room filled with ghouls and a big machine in the center of the bottom floor. The final two can be found on a shelf in the locked train car that can only be opened by siding with Bobbi No-Nose, as the key to the train car will only spawn on Fahrenheit's corpse.
Greenetech Genetics 3 On the top floor, two behind a security door locked at master level, and one behind a door further on locked at advanced level.
Gunners plaza 1 In a generator on the center of the roof, behind a door.
Haymarket Mall 1 On the scaffolding just outside the main entrance, on a closed cardboard box.
Near Jamaica Plain 1 On the floor in a house on the outskirts of Jamaica Plain, on the floor next to a dead feral ghoul.
Kendall Hospital 1 In the basement.
Longneck Lukowski's Cannery 1 In the basement area after the sewer section.
Malden Center 3 All near the generator after descending in the elevator. One is one the ground in front of the generator. The other is in the cardboard box on the table to the left.
Malden drainage 1 At the end of the canal just north of the Taffington boathouse.
Mass Fusion containment shed 1 Behind a mag-locked door (unlocked via terminal right above it).
Medford Memorial Hospital 1 West on the second floor in a generator room.
Merchants 1-5 Any merchant who stocks ammo will most likely carry up to 5 at 100% charge and may carry one or two others at a lesser charge (usually 40%-90%).
Milton parking garage 4 A part of one possible reward for completing the trap-ridden maze inside the parking garage.
Mole rat den 1 In a room to the right of the center room in the den.
Museum of Freedom 1 Lowest floor behind a security door (Novice terminal). Sturges asks the player character to retrieve it during When Freedom Calls. Unlike most other fusion cores, this one is obtained at a charge level of 50% instead of the usual 100%.
Mystic Pines 1 In the basement. The door to the basement is locked (Advanced) and requires 1 point in the Locksmith perk to pick.
Far Harbor (add-on) The Nucleus 2 On the metal shelves in the first wooden shack after the decontamination arches.
Nuka-World (add-on) Nuka-Cade 1 In the southernmost room, on the fusion generator.
Nuka-World (add-on) Nuka-Cola bottling plant 1 On the eastern part of the roof, inside a small cabin adjacent to the crane which accesses the faction flagpole. It is in a short cabinet between a tool case and a radio.
Nuka-World (add-on) Nuka-Town market 2 Aaron Corbett's counter.
Nuka-World (add-on) Nuka-World access tunnels 1 Just after passing the wooden bridge, inside the Gauntlet maze.
Nuka-World (add-on) Nuka-World junkyard 7 One can be found in a generator near a Port-A-Diner in the warehouse. Another can be found in the warehouse by jumping into a yellow gondola near the entrance from the second floor, but be warned it is hard to fit into the opening. While traveling through the tunnels to reach the Ultimate UFO, one can find another in the mouth of a bear statue after exiting the metro car. The fourth can be found in a metro car to the south of the Ultimate UFO on a shelf. Another can be found in a blue teacup south of the entrance to the Ultimate UFO. The final two can then be obtained from the sentry bot which guards the Ultimate UFO.
Nuka-World (add-on) Nuka-World transit center 1 On top of the yellow garage instrument table at the end of the tracks, near a pile of radioactive barrels.
Poseidon reservoir 1 On the main road at a military checkpoint north of the reservoir, in a suit of power armor.
The Prydwen's maintenance bay 2 Can be stolen off suits on the Prydwen by sneaking behind them.
Quincy church 1 In a crate, near the terminal inside the church.
Railroad HQ escape tunnel 1 Near the exit behind a security gate, which can be opened from the Expert terminal to the left of the door.
Recon bunker Theta 2 They can only be found during The Lost Patrol. One is in a generator while the other is behind the table Paladin Brandis stands behind upon entering.
Revere Beach station 1 Obtained for returning an overdue book at the arcade building near the station for fifty tokens.
Roadside Pines Motel 1 Behind the motel on the west side of the building.
Robert MacCready 1 As an active companion, he will sometimes provide one fusion core when initiating conversation with him.
Robotics disposal ground 3 In chest near the robot in the center of the room. Two more can be retrieved from the robot by enabling it and then self-destructing it.
Nuka-World (add-on) Safari Adventure 1 Next to the door of the AFAD base at the Angry Anaconda.
South Boston military checkpoint 1 In a power relay under the elevated freeway just east of the checkpoint.
Starlight Drive In 1 In the building behind the screen, behind a locked (Novice) door.
Suffolk County Charter School 1 In a generator in the basement.
Super Duper Mart 1 In the generator room in the back.
The Switchboard 2 Both can only be accessed during or after Tradecraft or by hacking a master-locked terminal. One can be found in a generator in a room on the south side of the big room with many desks and ruined terminals on the first floor. The other can be obtained next to a tool box behind an advanced-locked door near the elevator that needs to be turned on to function.
USAF Satellite Station Olivia 1 In the main center room in with the generator and the catwalk. Generator emits a buzzing sound.
Nuka-World (add-on) Vault-Tec: Among the Stars 1 Second monitoring room accessible from the residential room, south section, next the to Project Lead terminal.
Vitale pumphouse 1 In the second room, requires combination "10-4-5-1" to access.
Walden Pond gift shop 2 In a suitcase during the mission where one fights a group of raiders to liberate a village.
Waystation 1 When following Dogmeat during the Reunions quest.
Nuka-World (add-on) Welcome Center 1 In a small room to the left of the albino gatorclaw.
Wilson Atomatoys factory 1 On the outside in a generator, on the southern side of the factory.
Wreck of the FMS Northern Star 1 Inside a generator on the ground level, near the bow of the ship.
Yangtze 1 Inside an open footlocker in the crew quarters, to the west of the bathroom.
  • Sentry bots carry two or more fully charged fusion cores that can be recovered after the robot has been destroyed.
  • It is possible to pickpocket fusion cores from characters equipped with power armor such as Brotherhood of Steel members and Atom Cats. Successfully pickpocketing it will force its user to exit the power armor.


  • The item's value is independent of its charge level. The player can drain a fusion core almost completely (even if the charge reads 0/100, which means a charge of less than 1%) and still sell it for the same value as a completely charged core. A completely drained core, however, is removed from the player's inventory and is unable to be sold.
  • While in power armor the number of remaining fusion cores is displayed underneath the current fusion core's charge level. If 100 or more fusion cores are available, the counter will top out at 99 as it only has two digits.
  • A suit of power armor does not need a fusion core in it for a companion to enter it. If a fusion core happens to be in a companion's power armor, it does not drain from use.
  • Fast traveling does not drain energy from fusion cores while wearing power armor.
  • Using the jet pack drains the core's power much faster than any other action.
  • Leaving a fusion core in a power armor parked in a settlement may result in settlers, companions and even invaders wearing it. While the core will not drain, the power armor may be left in unexpected places. The power armor can be retrieved from settlers and companions by asking them to exit the power armor; it can also be retrieved from settlers by waiting for them to go to bed.
  • Fusion cores at different charge levels do not stack together.
  • If an NPC is wearing power armor, the fusion core can be targeted in V.A.T.S. Unless the player has the Penetrator perk, the fusion core has a hit chance of 0% when the player is not behind the NPC, otherwise the hit chance is the same as that of the NPC's torso.

Behind the scenes

In previous installments of the Fallout franchise, power armor was said to be powered by a TX-28 microfusion pack that can power the suit for over a century. It is never explained why a brand-new pack can be exhausted within 24 hours.


  • PCPC Xbox OneXbox One Sometimes, putting a fusion core into the armor may send both the fusion core or armor straight down, through the floor. Reloading a previous save is the only known fix.[verified]
  • Playstation 4Playstation 4 Xbox OneXbox One Completely draining a fusion core while in power armor and having a weapon not be fully loaded at the time may cause the game to show that the player character has no ammo for the said weapon. Solution: Unequip and re-equip the weapon.[verified]
  • PCPC Playstation 4Playstation 4 Xbox OneXbox One Having multiple fusion cores at the same level the power armor had when the Sole Survivor stepped into it may result in them all draining with the one in the power armor.[verified]
  • PCPC It is possible to acquire an infinite supply of fusion cores on the main deck of the Prydwen by stealing them from NPCs walking around in power armor. After stealing the fusion core from NPCs, they will exit the power armor and enter it again, which will spawn another fusion core in the NPC's inventory. This exploit can be repeated indefinitely; the only thing that can break it is saving and loading, which will cause a duplication glitch that spawns another empty power armor, and the NPC in the original suit will not be able to move. Leaving the area for some time and returning back may fix the glitched NPC and remove the duplicated power armor.[verification overdue]



  1. The Sole Survivor: "I'll help if I can."
    Preston Garvey: "What you'll need is an old pre-war F.C., a standardized Fusion Core. Your high-grade, long-term nuclear battery. Used by the military and some companies, way back when. And we know right where to find one..."
    Sturges: "But we can't get to the damn thing. It's down in the basement, locked behind a security gate. Look... I fix stuff. I tinker. Bypassing security ain't exactly my forte. You could give it a shot."
    (Preston Garvey and Sturges' dialogue)
  2. Berkeley Springs terminal entries; Dr. Barnaby's terminal, Medical Notes 10.31.77
  3. The Sole Survivor: "What're you looking for again?"
    Preston Garvey: "A Fusion Core. It's kind of a fancy battery. They used one here in the museum to power the exhibits, a long time ago. There's one in the basement, behind a security gate. You'll need to pick the lock or hack the computer to open it."
    (Preston Garvey's dialogue)
  4. Sturges: "That armor may be old, but it's got a standard interface. Just jack the Fusion Core in."
    (Sturges' dialogue)
  5. Electro-Fusion modification for the Hatchet
  6. The Sole Survivor: “The damage... it's deliberate. They set the fusion cores in their armor to overload. That's what caused the blast. But why?
    Spoken during The Lost Patrol