Capacitance Energy Calculator
Calculate energy stored, capacitance, or voltage using E = ½CV².
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What is Capacitor Energy?
Capacitor energy is the electrical potential energy stored in the electric field between a capacitor's plates. The energy is proportional to the capacitance and the square of the applied voltage:
E = ½CV²
Where E is energy in joules (J), C is capacitance in farads (F), and V is voltage in volts (V). This energy is stored in the electrostatic field and can be released almost instantaneously, making capacitors ideal for high-power pulse applications.
Common Capacitor Energy Reference Values
| Application | Energy (J) |
|---|---|
| Flash capacitor (100 μF at 300 V) | 4.5 |
| Large power capacitor (1 F at 2.5 V) | 3.125 |
| Supercapacitor (100 F at 2.7 V) | 364.5 |
| Camera flash (typical) | 10 |
| Defibrillator discharge | 360 |
| Small capacitor (10 μF at 5 V) | 0 |
| Electrolytic cap (1000 μF at 16 V) | 0.128 |
| Ultracapacitor bank (3000 F at 2.5 V) | 9,375 |
Related Calculators
Authoritative References
Frequently Asked Questions
What is capacitor energy?
Capacitor energy is the electrical potential energy stored in a capacitor's electric field. It is defined by the formula E = ½CV², where C is capacitance in farads (F) and V is voltage in volts (V). The energy is proportional to capacitance and the square of voltage — doubling voltage quadruples the stored energy.
How do I calculate energy stored in a capacitor?
Energy is calculated using E = ½ × C × V². For example, a 100 μF capacitor charged to 12 V stores E = 0.5 × 100×10⁻⁶ × 144 = 0.0072 J = 7.2 mJ.
What is the difference between capacitor energy and battery energy?
Capacitors store energy electrostatically in an electric field and release it very quickly, making them ideal for high-power, short-duration applications. Batteries store energy chemically and release it slowly over longer periods.
How does voltage affect stored energy?
Energy is proportional to the square of voltage (E ∝ V²). Doubling voltage quadruples the energy. Tripling voltage increases energy by 9×. This is why high-voltage capacitors can store significant energy even with small capacitance.
What is a farad in practical terms?
One farad stores 1 coulomb of charge at 1 volt. A 1 F capacitor charged to 1 V stores only 0.5 J of energy. Most practical capacitors are measured in microfarads (μF, 10⁻⁶ F) or picofarads (pF, 10⁻¹² F). Supercapacitors can reach thousands of farads.
How is capacitor energy used in circuits?
Capacitor energy is used in: camera flashes (rapid discharge for bright flash), defibrillators (controlled energy delivery), power supplies (smoothing voltage ripples), audio crossovers (filtering frequencies), timing circuits (RC time constants), and energy harvesting (storing small amounts of energy).