The effect of various electromagnetic boundary conditions on the propagation of surface waves in piezo‐electrics is considered. Basic for the analysis is the introduction of an electric ``surface impedance'' which relates the electric potential to the normal component of electric displacement in the surface. An analytic expression for this impedance is found in the case of weak piezoelectric coupling which permits the calculation of the phase velocity for arbitrary values of the impedance. It is also shown that within the weak coupling approximation the surface impedance contains the information on material parameters necessary for calculating the power transferred to surface waves from an impressed electric current.