Method to test solar cells or solar modules for electrical material degradation, in which - a current generated by the one or more solar cell(s) or the solar module is measured in time-resolved manner while the electrical voltage at the one or more solar cell(s) or the solar module is changed incrementally in order to determine an electrical capacitance of the solar cell(s) or the solar module as a function of the voltage on the basis of an electrical model of the solar cell(s) or the solar module, and - a degree or relative change in an electrical material degradation of the solar cell(s) or the solar module is determined from the voltage-dependent electrical capacitance by comparing it with reference values or an earlier measurement at the one or more solar cell(s) or the solar module, characterized in that in order to determine the voltage-dependent electrical capacitance at least two measurements are taken, of which - in a first measurement an electrical voltage is applied to the solar cell(s) or the solar module and changed incrementally in a first direction, and a current generated by the one or more solar cell(s) or the solar module is measured in time-resolved manner during each incremental change, and - in a second measurement an electrical voltage is applied to the solar cell(s) or the solar module and is either changed incrementally in a direction opposite to the first direction or is kept constant to establish a balance state in the one or more solar cell(s) or the solar module for different voltage values, and a current generated by the one or more solar cell(s) or the solar module is measured in time-resolved manner during each incremental change or for a respective constant voltage in the balanced state. - a current generated by the one or more solar cell(s) or the solar module is measured in time-resolved manner while the electrical voltage at the one or more solar cell(s) or the solar module is changed incrementally in order to determine an electrical capacitance of the solar cell(s) or the solar module as a function of the voltage on the basis of an electrical model of the solar cell(s) or the solar module, and - a degree or relative change in an electrical material degradation of the solar cell(s) or the solar module is determined from the voltage-dependent electrical capacitance by comparing it with reference values or an earlier measurement at the one or more solar cell(s) or the solar module, characterized in that in order to determine the voltage-dependent electrical capacitance at least two measurements are taken, of which - in a first measurement an electrical voltage is applied to the solar cell(s) or the solar module and changed incrementally in a first direction, and a current generated by the one or more solar cell(s) or the solar module is measured in time-resolved manner during each incremental change, and - in a second measurement an electrical voltage is applied to the solar cell(s) or the solar module and is either changed incrementally in a direction opposite to the first direction or is kept constant to establish a balance state in the one or more solar cell(s) or the solar module for different voltage values, and a current generated by the one or more solar cell(s) or the solar module is measured in time-resolved manner during each incremental change or for a respective constant voltage in the balanced state. - in a first measurement an electrical voltage is applied to the solar cell(s) or the solar module and changed incrementally in a first direction, and a current generated by the one or more solar cell(s) or the solar module is measured in time-resolved manner during each incremental change, and - in a second measurement an electrical voltage is applied to the solar cell(s) or the solar module and is either changed incrementally in a direction opposite to the first direction or is kept constant to establish a balance state in the one or more solar cell(s) or the solar module for different voltage values, and a current generated by the one or more solar cell(s) or the solar module is measured in time-resolved manner during each incremental change or for a respective constant voltage in the balanced state.