This paper describes and compares four different charging strategies for supercapacitors in the form of an RC circuit: charging with constant current; with stepwise voltage increase; with constant absorbed power; charging with constant supplied power. The third strategy describes a method that can calculate the current at which the supercapacitor circuit must be charged to absorb the required constant power. The fourth strategy describes a method that can accurately calculate the power necessary to be supplied to the supercapacitor circuit to charge it by a certain amount of energy at a given time. The charging efficiencies of all strategies are compared using Matlab models, simulating situations when the same supercapacitor circuit within each strategy is charged up from a certain initial voltage to a certain final voltage during equal times of charging. Simulation results show that charging supercapacitors with constant current is the most effective compared to the other strategies, but the percentage of this difference is only in the range of 0.1%. The experimental verification of the most efficient method is shown. The analysis could be useful for power backup application of the supercapacitors where charging time can be selected without significant restrictions.