This paper presents a new feature of the IDEA1 Wireless Sensor Network (WSN) simulation platform: its ability to run simulations on heterogeneous sensor nodes that compose a network. This platform allows system-level simulations with hardware accurate models, with graphical inputs and outputs to easily simulate such distributed systems. When comparing IDEA1 simulation results to physical measurements, difference is 6 percent. IDEA1 is more than three times faster simulation compared to another simulator (NS2). In the testbed we consider, the well-known IEEE 802.15.4 standard is considered and different microcontroller units (MCU) and radiofrequency units (transceivers) compose the heterogeneous nodes. Output curves, packet delivery rate (PDR), packet latency can be evaluated. Moreover, energy consumption of sensor nodes is detailed with a very fine granularity, at hardware and software level. Indeed, energy consumption of each internal block of each device on each node can be monitored with IDEA1. Therefore, it is possible to simulate quickly and accurately heterogeneous (hardware different) nodes. Indeed, multitude of hardware platforms and communication standards lead to inter-communicating heterogeneous networks. This simulation platform can be used to explore design space in order to find the hardware devices and IEEE 802.15.4 algorithm that best fit a given application with a constrained energy budget.