Defect-based single photon emitters are a very interesting option for quantum technologies. Unlike bulk-based emitters, two-dimensional materials provide advantages such as the possibility of forming van der Waals heterostructures. In them, the adjacent layers can be used to control or modify some properties, often in a controlled way. In this work, we show that the emission energy of single emitters is affected by the potential exerted by an adjacent insulating layer. We applied this insight into the hexagonal boron nitride bilayer, and depending on the actual defect and stacking order, the emission energy can be changed in the range of similar to 10-400 meV.