This paper presents a model for the calculation of irradiation for large bifacial PV power plants. The represented model, convenient for hourly meteorological data, enables calculations of typical daily and annual electricity production (AEP) of PV power plants. The results of comparisons of the proposed model that takes into account the fact that not all the diffuse irradiation incident on the surface between PV rows and the existing irradiation models justify proposed irradiation model. The significance of the proposed model is highlighted for bifacial PV power plants due to significant share of reflected irradiation component in production bifacial PV power plants. Depending on a reflection coefficient of the surface between PV rows and the distance between PV rows, a deflection of the production based on the proposed and existing model of irradiation can reach even more than 20%. For the same reflection coefficient of the surface between PV power plants, the production of bifacial PV power plant is bigger even for more than 20%, and LCOE smaller for 8.7% in comparison with monofacial PV power plants. Taking into account the power plant owners' interests in profit maximization, it has been shown that it is economically justifiable to mount reflectors between PV rows in bifacial PV power plants in case when the reflection coefficient is above 0.6 provided that its price does not exceed 7.4(sic)/m(2).