The Brazilian electricity matrix is around 80% renewable, and it has registered continuous growth in the expansion of biogas and photovoltaic (PV) systems. The main current Brazilian incentive program for the distributed generation of renewable energy, through a single net metering tariff, that is, a generation compensation system in credits to the consumer who owns the generating unit, does not seem to be effective to promote the expected growth of the biogas. Thus, the objective of this paper was to evaluate quantitatively and qualitatively a set of significant externalities for both sources to contribute to a more realistic energy planning. The externalities quantitatively evaluated for these two renewable sources were: avoided emissions, employment and income, biofertilizers for biogas and use as a constructive element for PV systems. A significant result was that the economic value of the externalities of biogas can exceed those of PV systems for the rural producer by more than 11 times, for society by 1.7 times. It is concluded that, due to the value of biogas externalities being much higher economically than those of PV systems, Brazilian public policies for energy planning should prioritize biogas over solar photovoltaic energy systems.
