There is no real obvious way to do this in GURPS.
- DR with Absorbtion lets you regenerate HP or FP.
- Healing lets you spend FP to heal others HP (or other injury).
- Leech lets you drain someone elses energy to heal yourself.
- Regeneration can be bought for FP.
Those are good options for taking, not giving.
You can use an Affliction or Affects Others to let someone have one of the above abilities but that requires them to use it. Doesn't work too well if your charging up a battery or something and it just doesn't have the right feel.
So what do we do?
Healing and Leech could just be hand waived as new advantages that reversed the effects. Healing would let you transfer any amount of FP to another, while Leech is limited to 1 FP per level.
The latter feels the best to me so here is a variant totally not cannon advantage.
25 + 4/level
You can transfer your energy to an unresisting or helpless subject. This requires touch on a willing subject or a grapple on an unwilling one. The energy must fit a specified source and can only transfer energy to beings or objects that can contain the same energy, this includes Energy Reserves.
It costs the user 2 FP per FP the subject receives, and is limited to 1 FP received per level per turn.
Examples Sources: Chi, Divine, Heroic, Magic, Spirit, Vitality (normal FP), and mundane sources such as electricity.
- Efficient Transfer, +25% allows you to transfer on a 1 to 1 basis.
- Hazard, varies. can restore FP lost to the specific hazard (Dehydration, lost sleep, suffocation, etc,) in addition to normal FP loss. Use the typical modifier for Hazards and halve it (round up).
- Malediction, varies. Your able to concentrate and gather the energy around the subject instead of shooting a beam. Use normal Malediction modifiers, Ranged is not required, as it is for Leech.
- Range, +40% allows you to project a beam of energy over a distance, uses normal range modifiers and can be increased with the normal modifiers.