To fully exploit the next generation of process technology, a system approach to low power is needed. The challenge is to avoid 'dark silicon' which is prohibitively expensive to 'light up' from an energy point of view. To mitigate this, all aspects of system design have to optimised, even though each may only make a small contribution to energy efficiency. What matters is the product of all of these improvements, from transistor level through SoC architecture and up in to the software stack. By working in partnership, engineers from across the industry can apply new techniques to reduce power in all parts of the system. This presentation will describe work ARM is doing in physical IP, interconnect, and processor sub-systems to enable energy efficient systems. It will also discuss the importance of system profiling and analysis, and definition of new industry standards.