Arrandale Ultra Low Voltage has 18W TDP
 

In Q1 2010 Intel plans to launch its upgrade for ultra low voltage dual core platform. Current king of ultra low voltage, the ultra thin notebook SU9600 will get replaced by the dual core, Core i7 640UM.

Many will be confused by the fact that Core i7 640UM has 80 percent higher thermal design power, or 18W compared to 10W to SU9600, but you have to
remember that the Core i7 640UM, also known as Arrandale also has an IGP inside that is contained within this TDP.

http://www.fudzilla.com/content/view/15448/35/