Calculate energy stored in capacitors using E = ½CV². Supports series and parallel combinations with charge, peak current, and RC time constant outputs.
Capacitors store electrical energy in the electric field between their plates. The stored energy follows E = 1/2CV^2, so voltage has a much larger effect than capacitance alone: doubling voltage quadruples the energy.
This calculator computes stored energy, charge, peak discharge current, and RC time constant for single capacitors or series and parallel banks. Enter the capacitance and voltage rating, then add the number of units if you are evaluating a bank rather than one component.
Preset examples cover small timing circuits, camera flash capacitors, and other high-energy cases where knowing the stored joules matters for design and safety.
Capacitor energy calculations are easy to misread when a bank is wired in series or when voltage, charge, and current are discussed separately. This calculator keeps those relationships together so you can see how the same component behaves under different configurations.
That is useful when selecting parts, checking discharge behavior, or comparing how much energy a design can actually store before it is energized.
Energy E = ½CV² (joules). Charge Q = CV (coulombs). Series: C_total = C/n, V_total = nV. Parallel: C_total = nC, V_total = V. RC time constant τ = RC. Peak current I = V/ESR.
Result: 14.85 J
A camera flash capacitor (330 µF at 300V) stores ½ × 330e-6 × 300² = 14.85 J — enough energy to produce a bright xenon flash lasting milliseconds.
A standard electrolytic capacitor stores about 0.01-0.1 Wh/kg, compared to lithium-ion batteries at 100-250 Wh/kg. However, capacitors can deliver their energy in microseconds to milliseconds, giving them power densities of 10,000+ W/kg versus batteries at 250-1000 W/kg. This makes capacitors ideal for pulsed applications.
Supercapacitors (ultracapacitors) bridge the gap between conventional capacitors and batteries with capacitances from 1 to 3000+ farads. They use electrochemical double-layer charge storage and can deliver high power with hundreds of thousands of charge cycles. Applications include regenerative braking in buses, UPS systems, and burst power for IoT devices.
Charged capacitors can retain dangerous voltage for hours or days after power is removed, especially in high-voltage equipment like power supplies, motor drives, and CRT televisions. Always verify zero voltage with a meter and use proper discharge resistors. At voltages above 50V, capacitor discharge can cause burns or cardiac arrest.
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Energy = ½CV², where C is capacitance in farads and V is voltage in volts. The result is in joules. Since energy depends on V², voltage matters much more than capacitance for energy storage.
In series, total capacitance decreases (C/n) but voltage rating increases (nV). In parallel, capacitance adds (nC) but voltage rating stays the same. Series gives higher voltage; parallel gives higher capacitance.
Equivalent Series Resistance (ESR) is the internal resistance of a capacitor. It limits peak discharge current (I = V/ESR) and causes power dissipation as heat. Lower ESR is better for high-current applications.
The RC time constant τ = R × C determines how fast the capacitor charges or discharges through a resistor. After 5τ, the capacitor is >99% charged or discharged.
Yes — capacitors above about 50V can deliver painful or dangerous shocks. Large capacitors at high voltage (like camera flash units) can be lethal. Always discharge capacitors safely before handling.
Capacitors have much lower energy density than batteries. A typical AA battery stores ~10,000 J, while a 1000 µF capacitor at 25V stores only 0.31 J. However, capacitors can deliver energy much faster (higher power density).