Capacitor Energy Storage Calculator

How Much Energy Can a Capacitor Store?

Capacitors store energy in an electric field between their plates. Unlike batteries, they can release this energy almost instantaneously — making them ideal for filtering, power smoothing, and pulse power applications. The energy stored depends on both capacitance and the square of the voltage.

The Formula

E = ½ × C × V²

Where:

• E = energy in joules (J)
• C = capacitance in farads (F)
• V = voltage across the capacitor

Note the V² relationship: doubling the voltage quadruples the stored energy.

How to Use This Calculator

Enter the capacitance (in µF, mF, or F) and the voltage. Results show energy in joules, millijoules, and watt-hours (Wh) for large capacitors and supercapacitors.

Practical Examples

Example 1: 1,000µF capacitor at 50V. E = 0.5 × 0.001 × 2,500 = 1.25 J.

Example 2: Camera flash capacitor: 3,000µF at 300V. E = 0.5 × 0.003 × 90,000 = 135 J — enough to cause serious shock.

Example 3: 100F supercapacitor (ultracapacitor) at 2.7V. E = 0.5 × 100 × 7.29 = 364.5 J = 0.101 Wh. Useful for burst power but far less than batteries for energy density.

Safety Warning

Large capacitors store lethal energy. Always discharge capacitors through a load resistor before handling, and never short-circuit high-voltage capacitors.