Changes in energy consumption patterns after becoming a prosumer household are rarely associated with negative environmental effects, as prosuming is intuitively assumed to be emission-reducing. This paper demonstrates the importance of sufficiency-oriented energy prosumer behavior for climate neutrality goals by quantifying GHG emissions for photovoltaic (PV) prosumers at the German household and energy system level. Based on the results, recommendations are derived for promoting energy sufficiency in prosumer households.