This paper describes a standard for traceable measurements of electrical power of sinusoidal signals at voltages up to 1000 V, currents up to 20 A, and frequencies from 40 Hz to 200 kHz. The standard uses thermoelectric effects to relate the alternating power to that of known dc signals. It is comprised of a thermal power comparator, inductive and resistive voltage dividers, and a range of wideband current shunts. The performance of each of the components has been evaluated through traceable measurements in terms of fundamental standards. The paper presents the design of the system and its components, evaluation techniques, and measurement uncertainties.