Photovoltaic generation has reached high penetration levels in many countries. Photovoltaic like other variable renewables can have significant implications for the adequacy and operation of the power system and in general these implications can be location specific. This work focuses on the Lombardy region, in Italy, to study the implications that different penetrations of photovoltaic would have on the need for firm generation capacity and on the variability that this firm capacity would have to face. This is done by analyzing a the combination of real historical irradiance and demand data for the year 2012. Results show that even high penetrations of photovoltaic in the region would not reduce the need for firm generation. Moreover, high levels of generation from PVwould lead to higher and more frequent changes in generation. These considerations must be properly taken into account when encouraging the penetration of photovoltaic and when modeling power systems for planning purposes.