Piezoelectric actuators are typically preloaded with a modest mechanical compressive stress during actuation to reduce cracking and allow for operation in the dynamic range. In addition, actuators are required to carry out mechanical work during operation, resulting in a nonlinear relationship between stress and actuation voltage. In fact, mechanical loading can significantly impact the electromechanical performance of lead-free piezoelectrics. Herein, we report the dependence of electromechanical properties of CaZrO3 modified (K,Na)NbO3-based lead-free piezoceramics on uniaxial compressive stress, comparing to their lead-based counterparts. It is demonstrated that increased non-180 degrees domain switching enhances the strain output at a moderate stress of approximately -50MPa from room temperature to 150 degrees C. Larger uniaxial stress, however, is found to suppress ferroelectric domain switching, resulting in the continuous strain and polarization decrease.