Capacitor Energy Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026How capacitors store energy
Unlike a battery, which stores energy chemically, a capacitor stores energy directly in the electric field between its plates. The amount stored depends only on its capacitance and the voltage applied across it.
Worked example
For a 100uF capacitor charged to 12V:
Charge Q = C x V = 100uF x 12V = 1200 uC
Energy E = 0.5 x C x V² = 0.5 x 100uF x 12² = 0.0072 J
Frequently asked questions
Why does energy scale with voltage squared but charge only scales linearly? Charge is a simple linear relationship (Q=CV), but energy involves integrating the work done moving charge onto the plates as voltage rises from zero, which produces the squared term - doubling the voltage on a capacitor quadruples its stored energy, not just doubles it.
Where is this used practically? Camera flash circuits, defibrillators, and power supply smoothing all rely on capacitors charging up and then releasing this stored energy quickly, since capacitors can discharge far faster than a chemical battery of similar energy capacity.