How to Calculate and Optimize Your Electrical System's Power Budget

Created 7/21/2021last Updated 07/06/2023


Power budget or power estimate is an analysis process performed on the power delivery network (i.e., cables, voltage conversion regulator stages, etc.) from input to electrical or electronic loads by identifying the power consumed by each electrical functional block and the power dissipated during the power delivery. This analysis of power dissipation informs the designer of the actual total power consumption of the system and whether or not this meets the target power consumption and does not exceed the capability of the power supply unit. For example, a power supply unit such as a 500W power supply on your PC might handle a medium-tier graphic card but can't handle high-performance graphic cards because the power load on the graphic cards exceeds the delivery capability of the power supply unit.

In practice, the power budget is specified in watts (W) and is in the format of a spread sheet where input voltage, input current, output voltage, output current, power in, and power out are documented for each power stage and electronics load.

The Process of Estimate Power Budget of an Electrical System

To calculate the power budget of an embedded device, you need to consider the power consumption of individual components and subsystems within the device Here are the general steps to calculate the power budget: 

Note: Some regulators cannot have a low dropout, such as 300 mV headroom, and require a large input voltage for biasing internal circuitry (e.g., 1.7 V vin min for an LDO that regulators at 1 V). If the current is in the hundreds of miliampere range, this is acceptable. If the current is in the 1 to 2 ampere range, depending on the noise requirements, please use an SMPS or a low-dropout LDO that has a lower input voltage limit.

By following these steps, you can calculate the power budget of an embedded device and ensure that the power supply and power management systems can adequately handle the power requirements of the device. 

Example Spread Sheet

In this example, we have listed various components of the embedded device, including the CPU, memory, and GPU. For each component, we have provided the overall power consumption before and after power conversion stage.

The "Total" row provides the sum of the power consumption for all components, indicating the total power requirements of the embedded device. In this case, the total power consumption is 7.67 watts during active operation. This analysis process determines the power ultilization and loss in the power delivery work of the electronic product, which provides simple diagram for the flow of the power into the system.


This exercise allows the designer to understand the power consumption at each power stage, optimize for power loss, and therefore increase the power margin of the system.