Energy storage systems can cost-effectively balance fluctuations from renewable generation. Also, hydropower dams can provide flexibility, but often cause massive fluctuations in flow releases (hydropeaking), deteriorating the ecology of the downstream rivers. Expanding transmission infrastructure is another flexibility source but is frequently plagued by social opposition and delays. As the decision-making process transcends costs, we developed a multi-objective framework to design a fully renewable power system, such that the tradeoffs between total costs, hydropeaking, and new transmission projects can be assessed from a multi-stakeholder perspective. We planned the Chilean power system for the year 2050 and, based on the obtained trade-off curves (Pareto), we identified the following implications for the different stakeholders. Avoiding new transmission generates little costs (avoiding 30%/100% of transmission costs < 1%/ > 3%), which is positive for planners but negative for transmission companies. Severe hydropeaking can be mitigated for about 1% of additional costs if transmission is deployed. Avoiding both hydropeaking and transmission is the most extreme scenario, costing 11%. The less the transmission and hydropeaking, the more solar and storage technologies are installed. Cheap solar and storage systems enable policymakers to cost-effectively limit hydropeaking and new transmission, which makes the system greener and more socially acceptable.