The IoT is changing key aspects of our daily lives and the way several industries work, due to ubiquitous wireless connectivity, especially due to machine-type communications (MTC) with heterogeneous needs (massive connectivity, low latency, ultra-reliability) of different applications. However, those cannot be meet by current technologies nor by conventional broadband techniques; both not often designed to be energy efficient. ee-IoT tackles this issue by proposing an energy efficient IoT solution that includes: (i) differential treatment of different applications; (ii) pre-processing in the edge based on the specific application requirements and its traffic; (iii) characterization of distinct traffic regimes; (iv) joint design of the wireless communication system with data aggregation and pre-processing. ee-IoT builds theoretical, algorithmic and implementation (over two different test networks) bases for designing energy efficient MTC wireless networks for systems of the future.