Capacitor Energy & Charge Calculator
Calculate energy stored and charge in a capacitor, or find the capacitance needed to store a target energy.
Capacitor Parameters
V
Results
Energy (E)7.200 mJ
Charge (Q)1.200 mC
AA battery equivalent (1 AA ≈ 10 800 J)1/1.5M of a AA battery
Capacitor Energy Storage
A capacitor stores energy in its electric field. The energy depends on both the capacitance and the square of the voltage — doubling the voltage quadruples the stored energy, while doubling capacitance only doubles it.
This makes voltage the dominant parameter for energy storage. Supercapacitors (also called ultracapacitors or EDLC) exploit extremely high capacitance (1–3000 F) to store significant amounts of energy, bridging the gap between conventional capacitors and batteries.
Stored Energy
E = ½ × C × V²Stored Charge
Q = C × VRequired Capacitance
C = 2E / V²Key Points
- Energy scales with V² — higher voltage means far more energy
- A 400 V, 1000 µF camera flash capacitor stores 80 J
- A defibrillator capacitor stores ~200–400 J at ~2000 V
- Supercapacitors (1–3000 F) can start car engines
- Capacitors discharge instantly; batteries discharge slowly
- Never exceed the capacitor's rated voltage — risk of explosion
Applications
- Camera flash units
- UPS hold-up capacitors
- Rail gun and pulsed power systems
- Supercapacitor energy storage and backup
- Power supply bulk capacitors (ripple filtering)