Infrastructures have recently been conceptualised as in process and dynamic rather than fixed and obdurate. We introduce the notion of infrastructural value to draw attention to the specific value that can be produced in something in relation to its participation in an infrastructure, its operation and management. We analyse demand-side response (DSR) as a case of infrastructural extension where value is produced in already-existing electricity consuming devices, generating a return for their response to the ends of grid management. We track the work of aggregators who enrol clients and their devices into providing combined synchronised responses contracted with the grid operator. This involves aggregators in activities of temporal prospecting, legitimation, optimisation and coordination. We argue that the notion of infrastructural value helps to articulate the relations between the fluidity and flexing of infrastructural boundaries and value making practices and consider other ways that this category of value might be explored.