Photovoltaic (PV) systems based on microinverters harvest more sun energy than traditional central or string inverters because shading of a PV panel within an array affects only that panel. However, cost is still an issue when competing not only with fossil-based energy sources but also with central or string inverters. The main cost of a microinverter is most likely not related to the semiconductor devices but to the heat management elements. Increasing efficiency should reduce heat removal requirements and thus lowering costs to a level where grid parity could be reached. Gallium nitride (GaN) transistors are wide bandgap devices with lower switching losses than silicon (Si) devices, and thus, reduced heat management requirements. A complete design of a dual-stage microinverter based entirely on GaN technology and a comparison with a silicon design are presented to evaluate the impact on system efficiency. Experimental results from a 200W prototype demonstrate the benefits of the proposed GaN-based design, in particular, a 4% improvement in the efficiency representing 8W of less dissipated heat in the active devices when the converter operates at 200W.