[Kwant] Full Quantum point contact Simulation

I have been trying to implement full Conductance measurements in bias and gate space of a quantum point contact. As I understand gate implementation is rather straightforward by generating on site potential. But when scanning this potential the energy parameter is fixed. What does the chosen fixed value of energy mean? Ideally one can integrate out the energy to get Conductance as a function of bias using Landauer formalism, is this approach correct? Or one can avoid this somehow in Kwant.