It is most important that a fuel be burnt in a fashion that shall least pollute the environment. In this regard every day new legislation are passed restricting emissions. A second important issue is to obtain high density thermal energy via enhanced volumetric heat release. Porous media combustion offer solutions that address both these issues. In this study, we performed several numerical analyses of a symmetrical two-dimensional problem to investigate combustion in a 5 kW porous burner and thermal efficiency of our design. Solution domain consists of four sub-domains, two porous regions in tandem (first with low porosity and second with high porosity), a water tank with constant flow rate and a solid wall in between those. In order to achieve our goals, methane-air is used as reactant mixture for combustion with different excess air ratios and for the purpose of optimizing our design various water flow velocities are tested for each excess air ratio. Navier-Stokes, energy (thermal equilibrium model) and species transport equations are solved in two-dimensional symmetrical model. A two step methane oxidation mechanism is utilized. Velocities, temperature distributions in both combustion zone and water tank, temperature distribution in the axial direction at the centerline of the combustion zone and heat transfer from combustion zone to water are presented.