This paper reviews the performance of the state-of-the-art solid oxide fuel cells that are fabricated using air electrode tubes, and discusses studies that are currently underway to reduce cell cost. A new design cell that combines the seal-less feature of tubular cells and a flattened air electrode with integral ribs is described; this design has a lower cell resistance and hence provides higher power output than tubular cells. Finally, the paper describes the operation of the 25 kW and 100 kW power generation systems that were built using such cells, and discusses the 250 kW pressurized SOFC-gas turbine hybrid system that is currently being built.