We present a distribution grid simulation study in which we analyse the aggregated impacts of individual prosumer optimization strategies for the operation of a typical European distribution grid. For this we simulate the individual behaviour of 4'000 prosumer households that have roof-top solar PV and residential batteries. They are using different operation strategies in order to maximize their own benefit with respect to variable residential electricity tariffs as well as their own load consumption and PV power production - for instance via PV self-consumption maximization. We analyse the aggregated impacts of the individual prosumer behaviour on the distribution grid. We show how the choice of the applied rule-set, respectively the economic incentives given to prosumers, is decisive for inducing either grid-friendly or grid-unfriendly prosumer behaviour.