In 2014, the Advanced Research Projects Agency-Energy (ARPA-E) launched the Reliable Electricity Based on ELectrochemical Systems (REBELS) program with the goal of pursuing alternate fuel cell materials and operating conditions that could enable system cost reductions and new electrochemical functionality. This presentation will briefly revisit the original REBELS vision by elaborating the potential benefits of operation in an intermediate temperature range of 200-500 C. Trends in the U.S. electrical grid will be discussed, which reveal the benefits of enhanced fuel cell functionality such as in-situ charge storage and gas-to-liquids (GTL) capabilities. The most significant technical accomplishments from REBELS project teams will be highlighted, including several examples in which the program objective of a current density of 200 mA/cm2 at 0.78 V and 500 C on methane fuel was achieved. Furthermore, teams were able to demonstrate thousands of hours of operation on internally-reformed methane fuel at 500 C with no evidence of coke formation. Fuel cells with charge storage functionality in or near the anode showed a more rapid response to large changes in current density and a lower voltage decrease with high fuel utilization. The needs for further techno-economic assessment to evaluate this concept will be highlighted. Progress towards fuel cells that can also convert methane to liquid fuels will be summarized. Finally, overall lessons learned from the REBELS program will be discussed, such as the ability of ceramic proton conductors to deliver high current density at 500 C on non-hydrogen fuels with minimal degradation. The need for future work in this field will be stressed, especially a continued examination of whether stacks in this temperature range possess the appropriate combination of performance and cost to accelerate the commercialization of high efficiency fuel cells worldwide.