The main objective of this paper is to analyze and evaluate the impact of time resolution when estimating self consumption and self-sufficiency in grid-connected photovoltaic facilities. The consumption data were obtained from a photovoltaic facility installed in Malaga (Spain). They were extrapolated to analyze other PV facility sizes for the same location. The size of the PV installation that generates an annual energy equal to the annual consumption has been estimated. This size has been used as benchmark size in order to generalize the results. The different time resolutions analyzed to estimate self-sufficiency and self-consumption parameters range from 10 s to one year. These different time aggregation levels are related to the different net-metering regulations. The results show that using hourly data overestimates these parameters compared to the results at smaller time resolutions; when hourly data are used instead of 10 s data, the differences between these parameters are around 9%. This may be due to the fact that this, and higher, time resolution does not take steady state voltages and power flows into account. Thus, increasing the time resolution can cause relevant information loss. Moreover, the results are also useful for analyzing different net metering systems by means of the self-consumption and self-sufficiency metrics. Self-consumption and self-sufficiency for the facility benchmark size range from 48% to 98% depending on the time resolution.