This paper contributes to the literature on urban climate change experiments by analysing ascribed advantages and challenges of organizing climate change experiments at the urban scale, and by examining how local actions translate into effect. We here distinguish between effects of experiments in achieving actual sustainability gains (‘goal-oriented objectives’) and instigating broader institutional change (‘process-oriented objectives’). Empirically, we analyse efforts related to energy supply in two Danish urban climate change experiments: The ‘CPH 2025 Climate Plan’ in Copenhagen, and ‘ProjectZero’ in Sønderborg. Our analysis poses considerable question marks over the importance of the advantages ascribed to urban climate change experiments including ‘authority advantages’ and possibilities of ‘engaging and mobilizing stakeholders’.