To answer the question ‘How much energy is consumed for a numerical simulation running on Graphic Processing Unit?’, an experimental protocol is here established. The current provided to a graphic processing unit (GPU) during computation is directly measured using amperometric clamps. Signal processing on the intensity of the current of the power supplied to a GPU, with noise reduction technique, gives precise timing of GPU states, which allow establishing an energy consumption model of the GPU. Energy consumption of each operation, memory copy, vector addition, and element wise product is precisely measured to tune and validate the energy consumption model. The accuracy of the proposed energy consumption model compared to measurements is finally illustrated on a conjugate gradient method for a problem discretized by a finite element method. Copyright © 2015 John Wiley & Sons, Ltd.