What is the equation for calculating the heat radiated by Solid-state Relays?

The amount of heat radiated by Solid-state Relays can be found using the following equation.

Heating value P (W) = Output-ON voltage drop (V) x Carry current (A)

For example, if a load current of 8 A flows from G3NA-210B Solid-state Relays, the following heating value will be obtained.

P = 1.6 V x 8 A = 12.8 W