In this paper we propose a complete system energy model based on non-intrusive measurements. This model aims at being integrated in fast cycle accurate simulation tools to give energy consumption feedback for embedded systems software design. Estimations takes into account the whole system consumption including peripherals. Experiments on a complex ARM9 platform show that our model estimates are in error by less than 10% from real system consumption, which is precise enough for source code application design, while simulation speed remains fast.