How long can capacitors store energy?

It depends on the leakage current of the capacitor. Since leakage current is considered a unwanted behavior, the spec on the datasheet is usually about ten times the actual leakage current. This is to guarantee a vast majority pass testing in manufacturing. read more

That depends on the type of capacitor it ranges from quality. Some can store it just a few seconds. While super capacitors have been able to store up to 50% of its energy for 30-40 days. read more

The energy stored on a capacitor can be expressed in terms of the work done by the battery. What capacitors store is energy. Specifically, they store it in an electric field. All the electrons are attracted to all the protons. read more

The energy stored in the capacitor remains. If the capacitor terminals are connected with a resistor, then the charges can move, so there is a current. The energy that was stored in the capacitor is converted to heat in the resistor, the voltage decreases, the charges become less imbalanced, and the field weakens. read more