The calorific value in power supply depends on power consumption as well as other electronic equipment. The calorific value is shown as following.

1 [Ws] = 1 [J]

It can be expressed in "cal" as follows as well.

1 [Ws] = 0.239 [cal]

For example, the power consumption of a power supply shown in the following spec can be calculated as follows.

[Spec]

• Output voltage: 5V
• Output current: 10A
• Efficiency: 80%
• Operating time: 1hr

Internal Power Loss: P 

= Active Power - Output Power
= (Output Voltage x Output Current / Efficiency)
- (Output Voltage x Output Current)
= (5 x 10 / 0.8) - (5 x 10)
= 12.5 [W]

Calorific Value: J 

= Internal Power Loss [W] x Time [s]
= 12.5 x 3,600
= 45,000 [J]
= 45,000 x 0.239
= 10,755 [cal]