The proposed study continues a series of articles devoted to design methods for the key energy parameters of a helium-neon (He-Ne) gas laser. An application of the previously proposed method for designing the emission power to lasers with the rectangle- and ellipse-shaped cross sections of active elements has been considered. An idea of effective mode volume was used, a calculation algorithm was presented, and a procedure reducing unwieldy calculations was put forward. Varying the parameter values made it possible to get a detailed picture of dependencies of the output laser energy on the geometrical parameters of objects under study. A comparison of the obtained results permitted to find optimal laser parameters for maximum output power. The calculation results of the radiation energy were established to agree well both with those of the laser gain for the given cross sections and those of the experimental data.