Power distribution grids all over the world are experiencing exponential growth in the number of distributed generators (DG), especially for small-scale, residential, and commercial rooftop photovoltaic (PV) systems. Electrical energy storage systems (ESS) allow for the decoupling of generation from consumption, addressing the issue of PV supply intermittency in the traditional electricity grid, and improving the potential penetration and widespread deployment of PV on the distribution grid. Several articles were reviewed to list and better understand the different variables that influence the technical and economic evaluation of a PV + ESS system. By proposing and applying a novel hybrid Levelized Cost of Storage (LCOS) analysis, the effects of adopting ESS in the Brazilian regulatory framework were evaluated. The proposed method is universal, and the Brazilian case study is presented to illustrate it. Results are compared with an alternative of PV-only systems in a flat tariff scheme and show that a sharp drop in ESS initial costs is required before PV systems plus storage become the best investment alternative for the end user. However, the PV + ESS alternative results in a positive impact for the whole grid, suggesting that policies towards cost reductions and incentives, such as a wider Time-of Use tariff spread, should be designed to stimulate the adoption of ESS associated with DG solar PV.