The combination of wind turbines with fuel cells (FC) and electrolyzers (ELY) is an option for balancing fluctuating grid power injections from renewable energy sources. The conversion of electricity to hydrogen via ELY is often called "power to gas", while transforming hydrogen to electricity via FC is referred to as re-electrification. The application of these technologies currently faces high costs and finding a positive business case is challenging. This study quantifies the economic potential of marketing FC/ELY systems' flexibility. Their potential to reduce wind farm forecast errors as well as the system's ability to provide secondary control reserve (SCR) in Germany is investigated. For this purpose, data for the year 2013 is used. Different root mean squared errors and a probability density function (PDF) for forecast errors are considered. SCR dispatch power in high temporal resolution is approximated and different bidding strategies (SCR market) are taken into account. Results show that both applications can be economically viable, also when being combined. However, profitability is highly dependent on the system's configuration as well as its operating strategy. (C) 2016 Elsevier Ltd. All rights reserved.