How do I calculate the current consumption and power dissipation?

Fig. 2 shows how to measure the output power dissipation.
In case of BTL^*1 amplifiers, connect a load resistor acting as an equivalent to a loudspeaker between the output terminals, and measure the AC voltage (rms) across the load resistor with an AC voltmeter.
The output power is calculated using the obtained AC voltage and load resistance value. (Output power = AC voltage ^2/Load resistance)

Finally, the power dissipation is calculated by the following formula.
Power dissipation Pd = Input power: Pin - Total output power : Pout(Total) = BATTERY voltage: Vbat * current consumption: Iin – output power/1ch * Number of channels N (for multiple amplifier product when each output power is same)

Note that accurate results cannot be obtained if a voltage drop occurs due to wiring resistance, etc. during measurement. To avoid it, our recommendation is to measure the voltage near the terminals of the audio power IC.

As a reference, an example of 4-channel audio power IC is shown as below.
When BATTERY is 14.4V and the output power is 1W for each channel, power dissipation is calculated as follows.
BATTERY voltage: Vbat = 14.4V
Current consumption: Iin = 0.8A (measured)
Output Power: Pout = 1W (per channel)
Number of channels: N = 4 channels

Power dissipation : Pd = (Vbat * Iin)- (Pout * N)
　　　　　　　　　  　 = (14.4 * 0.8) – (1 * 4)
　　　　　　　　　      = 11.52 - 4
　　　　　　　　　      = 7.52 [W]

This calculation shows the intersection of the dashed lines in Pd vs output power chart in Fig. 3.