3D modeling for fuel cells is generally computationally expensive, especially for stacks. In order to reduce computational cost, spatial smoothing over the parallel plain channels in flow fields is introduced and applied to a 3D steady-state isothermal planar solid oxide fuel cell model, which is validated with experiment from literature. The 3D model is reduced to 2D coupled with effective parameters and correlation factors, and then asymptotically reduced to parabolic PDEs and ODEs associated with space marching. The correlation factors, which are derived based on a full set of governing equations for electrokenitics over a cell cross section, can handle not only variations in diffusion pathways due to ribs but also the coupling effect between governing equations. The reduced models are verified with the 3D counterpart in view of global and local properties. Good agreement with a quantitative loss of information is achieved. The reduction in computational cost is investigated. (C) 2013 Elsevier Ltd. All rights reserved.