Speculative Fiction and Fantasy have a great many devices, vessels, abilities, and powers, and they have to run on something! That is what this trope is about. Be it Phlebotinum, Dilithium Crystals, Mana, electric catfish, or spinach, there are many and varied Power Sources for a story's fantastic features to run on.
Power Sources have two basic characteristics: Nature (natural, scientific, magical; neutral, good, evil) and Replenishment (infinite, automatic, harvested, finite). In terms of Replenishment, some power sources are naturally replenishing and perhaps limited only to "needing an hour to cool off" or a good night's sleep. Others need to be harvested in some way, be it a vampire feeding off humans or a robot plugging into a wall. Other power sources are "always full," or "infinite", so a hero or starship never has to worry about refueling. This can remove a source of plot complications, and may seem a bit unfair when others get their Power at a Price. Thusly, these tend to get stolen or short circuited. A lot.
In terms of Nature, the sky is the limit. Two heroes with exactly the same power can fuel it with different things, or some can use exactly the same Power Source for two radically different powers. For an especially interesting dynamic, a hero and villain may be powered by mutually weakening energies, for example one using The Power of Love to fight a Hate Fueled foe.
This and How to Give a Character Superpowers overlap when without the Power Source the character has no powers... it's not the character needing the Power Source to fuel the powers, but the Power Source that also imparts the powers.
Here are some sample Power Sources.
Magical power sources include:
- Emotions - They can be used for self-nourishment, to empower an attack, or to fuel certain forms of Magitek.
Scientific* power sources can be:
- Extradimensional Power Source: A Pocket Dimension serving as a source of energy/power.
- I Love Nuclear Power: Nuclear/radioactive material.
- Lightning Can Do Anything: Plain old Electricity.
- The Power of the Sun: The Sun, either as photovoltaic energy or as a mystical entity.
- Pure Energy: "energy" itself treated as a discrete substance.
- Super Serum: Drugs, medication, or even an engineered retrovirus.
Artificial power sources are usually:
Mundane power sources can be:
- Food — They not only have a Hyperactive Metabolism, but need food for the energy to use their powers.
- Power-Up Food - Eating or drinking a certain food provides powers.
- Stamina — The hero can use their powers with no real "fuel" limitations, only being limited by natural well being and endurance.
- Hamster-Wheel Power is the comedy version of this variant.
- Gasoline — Or wood, there are steam punk suits of Power Armor.
Morality-Neutral, Good, and Evil power sources may include:
- The Dark Side
- Deal with the Devil
- The Lifestream
- Living Battery
- Powered by a Forsaken Child
- The Power of Friendship
- The Power of Hate
- The Power of Love