We have demonstrated the use of low-cost sensing devices for intelligent control of typical commercial energy loads: cool rooms for keeping produce fresh and heating, ventilation, and air-conditioning (HVAC) systems for buildings. We provide the sensing devices - Berkeley Motes and X10 sensing and switching equipment - with a presence on the internet to permit sophisticated applications to access their data and control their electrical loads. The ad hoc sensor network is connected to the mobile phone network through a light-weight gateway for long-hall communications. Local control provides failsafe default behaviour in the absence of remote control or when communication is lost. We will use this network to deploy agent-based software to manage distributed energy resources, including local generation plants as well as loads. Our aim is to provide new ways for small-to-medium enterprises, energy retailers, and energy network businesses to obtain commercial benefits in a deregulated energy market.