The invention relates to micro fuel cell systems whose performance is enhanced by an accurate fluid delivery system. The fluid delivery system improves reactant fluid provision to meet electrical output, while maintaining correct stoichiometries for chemical processing in a downstream reactor. The fluid delivery system includes a pressure source and a differential flow meter. The differential flow meter uses a flow restrictor and a sensor. The pressure source moves a fluid through the flow restrictor; the sensor detects differential pressure in the flow restrictor and outputs a signal that permits dynamic control of fluid flow, e.g., by controlling a pump.