Long-term stable and robust stack technology is a pre-requisite for a successful implementation of SOFC in the market and so it is one of the main issues in SOFC development. Also bigger stacks are desirable for systems with increased power output. Progress in stack and systems development is illustrated. Enhanced thermo-mechanical robustness of stacks in the kW range was demonstrated by successfully cycling a five layer stack incorporating cells of 20 x 20 cm(2) 100 times between 200 and 700 degrees C. Aiming at the utilization of anode-supported cells from other manufacturers, the design was modified to a window frame layout, integrating in this case four 10 x 10 cm(2) cells in one layer. A 20 kW system was operated for about 7000 hours in total, thereby demonstrating the suitability of the module and system concept. As special highlights, long-term tests with short stacks have now reached operation times of 66,500 h and 34,500 h, respectively. As a relatively new subject, activities entailed by high temperature electrolysis are briefly outlined. (C) 2015 The Electrochemical Society. All rights reserved.