|Requirement of electrical energy is in order to operate various domestic and industrial devices like ap-pliances, equipment and machinery. Electrical energy per time unit represents electrical power transferred. Well knowing the electrical power is very important because of economical aspects. Electrical power, an important element of an energy system, which considers elements like harmon-ics and phase between voltage and current, influence the cost and elements component of electrical power grid. This paper presents the evaluation of mark-space method of elec-trical power system. This method represents a mathematical approach, simulation, and analog implementation solving the power measurement suitable for single-phase network and DC circuits. The schematics developed consist of well-known electronic circuits like the pulse width modulation (PWM), filtering with operational amplifier, and absolute value of signal. This approach avoids multiplying operations that aid error generating. The main purposes are to track the performance of such a circuit in different operating sit-uations and present the schematic. Thus, influence of phase between voltage and current, influence of waveform shape regarding result using analyzed method, and characteristic linearity are example of tests perform. The results con-firmed the theoretical principle being analyzed using specif-ic simulation programs like LTSpice or Scilab, but not re-stricted to them.