The direct utilization of CO2 from flue gas bypasses the need for costly carbon capture and purification processes and thus presents a potentially more economical approach to create chemical feedstocks and fuels. In this work, essential system design parameters required for a CO2 electrolyzer to perform efficient electroproduction of formate from a simulated flue gas feed at industrially relevant activities have been identified. In addition to the use of effective catalysts and gas-diffusion electrodes, we demonstrate that the efficiency of formate production in a dilute CO2 environment is highly sensitive to the feed flow rate, which is directly related to the local CO2 concentration. If the flow condition is not optimal under dilute CO2 conditions, the carbonation reaction dominates and limits CO2 availability for formate production. Ultimately, we have established basic system design guidelines to overcome CO2 deficiency in a flue gas conversion electrolyzer without the need of a costly high-pressure system.