Derating is the operation of a device at less than its rated maximum capability to prolong its life. It is a protective measure that allows the use of electronic components and devices at high temperatures, high altitudes, or in alternative mounting orientations. Derating can also provide a safety margin for transient voltages or currents that exceed normal operation or prolong life. The process involves running the system or component at a lower voltage or current, generating less heat, and can be applied to almost all electronic components, including resistors, diodes, transistors, thyristors, LEDs, ICs, CPUs, capacitors, and others.

Derating is necessary for almost all industrial power supplies above a certain temperature, installation altitude, or in a deviating mounting orientation. Most power supply manufacturers specify ratings for lifetime, output current, and reliability for their products, but this information only applies under certain environmental conditions. The temperature limits must be observed so that the components in the power supply do not overheat or wear out prematurely. Derating is a recommended protective measure for electronic components and devices to protect them from high temperatures and prevent failures.

Derating analysis is a product reliability test that helps determine if there are any underspecified components in a product. It is used primarily for electrical and electronic devices and tests products by determining critical components maximum capabilities and then discerning which should be swapped for those with greater capacities to increase the overall reliability of the product whole. Derating analysis applies stresses on critical components to discover the weaker links and small design margins. These weak links are then upgraded with components that have greater design margins and tested for improved longevity so that the product whole fails less often, increasing its reliability, durability, and life expectancy.