Incumbent energy companies navigating the energy transitions: Strategic action or bricolage?

•We draw on the concepts of strategic action fields and arenas of development to study ruptures in the field of sustainable energy.•We present empirical case studies on collaborative projects of two powerful municipally owned energy companies in Finland.•Experimental arenas force the incumbent energy companies into interaction with new actors.•City-internal challengers can destabilize established market alliances and long-held rules in the city energy SAF.•A consideration of both perspectives can offer new insight on real-time attempts to promote a sustainable energy transition.