Operating temperature is the range of ambient temperatures within which a power supply can operate safely while meeting its performance specifications. It is typically expressed as a range, such as 0℃ to 40℃.
Unless otherwise specified, this rating is based on the unit being placed horizontally in still air. Operating the unit under different conditions, such as mounting it vertically or at an angle, may affect its performance.
For power supplies with forced-air cooling, the operating temperature is measured at the air intake.
Note on Lifetime: The operating temperature significantly impacts the power supply's lifetime. A common rule of thumb is that for every 10°C increase in operating temperature, the expected lifetime of the unit is halved. Therefore, operating the power supply at the lower end of its specified temperature range is recommended to maximize its longevity.