Designing low power complex embedded systems is now a critical challenge for a large number of electronic corporations. Low power is generally critical due to its impact on lifetime, battery longevity, battery capacity, temperature constraints, etc. Unfortunately, when a designer needs some power estimations about its design, the methods and tools which can help him are not sufficient. Indeed, there is a lack of efficient methodology and accurate tool to obtain power/energy estimation of a complete system at different abstraction levels. This paper addresses this problem and proposes a global framework for power/energy estimation and optimization of heterogeneous MultiProcessor System on Chip (MPSoC). This framework supports both a power modeling methodology and a power platform estimations which can help the designer to choose the best solution for his design. The methodology supported takes into account all the embedded system's relevant aspects; the software, the hardware, and the operating system. It includes several estimation tools with respect to their abstraction levels in order to cover the overall design flow. Starting from functional estimation and down to real boards measurements, our platform helps designers to develop new power models, to explore new architectures, and to apply optimization techniques in order to reduce energy and power consumption of the system. The usefulness and the effectiveness of the proposed power estimation framework are demonstrated through a typical embedded system conceived around the Xilinx Virtex II Pro FPGA platform.