The increasing number of installed renewable power generators, e.g. photovoltaic systems, leads to a significant growth of power electronic devices, especially in public low voltage networks. To analyze and assess the harmonic emission and the harmonic stability, i.e. the device characteristics in the frequency range up to 2 kHz, suitable device representations are required. The representation of commercially available devices is limited to black-box models since their detailed design is unknown. For the parametrization of the respective small signal models, all relevant impact factors on the model have to be known. Consequently, this paper studies the impact of the DC power on the small signal model of single-phase photovoltaic inverters. The paper presents a quantitative assessment of three commercially available inverters in terms of their frequency-dependent small signal characteristics. The linear time-invariant and the linear-time periodic device characteristics are analyzed in terms of their absolute and their relative deviations between different DC powers. The results demonstrate the importance of considering the DC power level for accurate frequency domain models in harmonic studies.