Abstract : Electron dynamics and energization are a key component of magnetic field dissipation in collisionless reconnection. In 2D reconnection, the main mechanism that limits the current density and provides an effective dissipation is most probably the electron pressure tensor term, that has been shown to break the frozen-in condition at the x-point. In addition the electron- meandering-orbit scale controls the width of the electron dissipation region, where the electron temperature is observed to increase both in recent MMS observations as well as in laboratory experiments (MRX). By means of two-dimensional, full-particle simulations in an open system (Pei et al. 2001; Ohtani and R. Horiuchi 2009), we investigate how the energy conversion and particle energization depends on the guide field intensity. We study the energy transfer from the electromagnetic field to the plasma, and the threshold guide field separating when parallel and perpendicular energy transfers dominate, confirming recent MRX results, in agreement with MMS observations. We calculate the energy partition between fields and kinetic and thermal energy of different species, from the electron scales to ion scales, showing there is no significant variation for different guide field configurations. We study electron distribution functions and self consistently evolved particles orbits for high guide field configuration, investigating possible mechanisms for electron perpendicular heating. Finally I will give an idea of our 2D simulations with plasmoids for which the setup can be easily extended to study 3D reconnection, thanks to GPU technology.