Arduino is a collection of Open Source, conventiently programmable microcontrollers designed for educational purposes. Its widespread popularity have made them somewhat of an industry standard for DIY and Open Source automation.
Because they are Open Source, widely available and well supported both by the producers as well as the community they might make an excellent core component ‘central brain’ for the Energy Router.
Suggested controller: Arduino Ethernet
Rationale: low-power device with TCP/IP and ethernet implemented in hardware. Ethernet is a hard requirement as reliability is important and wifi is, generally, unreliable and requires a significant amount of configuration.
Alternative option: something that interoperates with Spark