What is the unit of Q? Posted on August 16, 2022 By admin_zxviwxhy So, the units for Q are Joules (energy) divided by area (square meters) and time (seconds). Joules/(m^2∙sec). Since power is defined as energy divided by time and 1 Watt is equal to 1 Joule/second, Q can also be expressed as Watts/m^2 .