The paper presents the performance estimation analysis for wireless power transfer (WPT). The proposed estimation approach is based on the two-frequency harmonic balance method (2F-HB) for RF-DC conversion estimation and 3D electromagnetic waves propagation simulation under the real-world scenario. The 3D electromagnetic wave propagation simulation is performed in Ansys HFSS, to examine the impact of the laboratory dimensions, furniture placement, as well as the antenna gain on the power transfer efficiency estimation accuracy. The 2F-HB method is selected, as it allows for fast and accurate RF-DC power conversion efficiency estimation for the voltage doubler circuit used to perform RF-DC power conversion. The theoretical results are compared with the experimental ones obtained for the fabricated circuit prototype in laboratory conditions with interior layout made close to that of the 3D model. The potential applications of the proposed WPT model include autonomous sensor node deployment, harvesting circuit topology optimization, and the study of the effect of a power-carrying signal waveform on the overall WPT system efficiency for a given indoor environment and use case.