Mechanisms for tracking power unit usage allow power units to be exchanged rather than recharged. Users can purchase power unit subscriptions that are tracked on a per entity basis to allow exchange of power units during the subscription period. The subscriptions can also account for life cycle costs of the power units. Subscriptions can be based on a time period, on an amount of power, and/or on a number of power unit exchanges. In one instance, power unit vending stations interact with a centralized server to allow power unit exchanges at any number of disparate locations.