A capacitor stores electrical energy in the electric field between its plates.
A capacitor stores electrical energy in the electric field between its plates. The amount of energy it can hold depends on its capacitance and the voltage across it. This calculator finds that stored energy in joules.
A 100 µF capacitor is charged to 12 V. Energy = 0.5 × (100×10⁻⁶) × 12² = 0.5 × 0.0001 × 144 = 0.0072 J.
Energy (joules) = 0.5 x capacitance (farads) x voltage squared.
Voltage has a squared effect, so doubling voltage quadruples stored energy, while doubling capacitance only doubles it.
It's released into the circuit, which is why capacitors are used for quick energy bursts like camera flashes.