Capacitor Wattage Guide
Capacitors do not work like simple resistors. A perfect capacitor stores and returns energy. It does not turn that energy into heat. Real capacitors are different. They have ESR, dielectric loss, ripple limits, voltage limits, and thermal limits. This calculator separates those values so the result is easier to understand.
Reactive Power
In an AC circuit, a capacitor creates capacitive reactance. This reactance controls current flow. The product of RMS voltage and capacitor current gives reactive wattage in VAR. This value is important in motor circuits, power factor correction, filters, and AC supply design. It is not the same as real heat wattage.
Real Heat Wattage
Real wattage appears when the capacitor has internal losses. ESR converts ripple current into heat. The dissipation factor estimates dielectric loss. These losses can warm the part and shorten its service life. High heat can dry electrolytic capacitors. It can also weaken film or ceramic parts. Always compare the calculated current with the rated ripple current.
Stored Energy and DC Charging
For DC use, the calculator estimates stored energy in joules. It also estimates average charging wattage when a charge time is entered. This is useful for pulse circuits, power supplies, flash units, and backup circuits. The actual charging curve can change with resistance, source limits, and switching method.
Practical Design Notes
Use a voltage rating above the working voltage. The safety factor field gives a quick suggested rating. Higher safety margins are useful in hot areas, unstable supplies, or long life designs. Always check the capacitor datasheet before building a final circuit. The calculator is a design aid. It should not replace manufacturer ratings, testing, or electrical safety rules.