This paper proposes a methodology to evaluate the energy cost of an industrial user before and after a Photovoltaic generator (PVG) is started, in order to observe the penalty cost of the power factor (PF) due to the imbalance of the required energy components for an overall load when starting a PVG. This methodology proposes to probabilistically estimate parameters which are not 100% predictable, such as temperature and radiation, which, combined with the installation characteristics of a PVG, allow estimating the amount of energy that a generator can provide and the consumption components of an active and reactive energy load in order to establish the energy costs per month. An analysis of the energy consumption behavior will follow once the generator is involved into the process, considering the active energy contribution from itself, while evaluating the PF. Once again, the monthly energy costs are set and the possible cost overruns for PF penalties are considered. As a case study, this methodology was implemented in an industrial user located in Bogotá city, having in mind the local regulations to find out that when a photovoltaic generator is started, approximately 15% of the energy consumption costs for 1 year corresponds to PF penalties.