In this paper, we report on numerical calculations of stationary thermoelectric responses in a metal/dot/metal junction. We derive the Landauer expressions for both the electric and the heat currents, and first discuss the question of heat balance. Secondly, we calculate the Peltier coefficient in the non-linear response regime, and discuss its relation with the Seebeck coefficient, and finally the figure of merit ZT in the linear response. In all regimes, we show how the applied gate voltage is a key parameter to obtain the maximum thermoelectric efficiency through the nanodevice.