Documentation

Calculation Methodology

Last updated: July 13, 2026

This page provides transparent, technical documentation of every formula, multiplier, and assumption built into the PSUCheck calculation engine. No black box estimations.

1. Sustained System Draw (Base Draw)

The base system power draw is calculated by summing the sustained power ratings (TDP/PL2) of all components:

Base Draw (W) = CPU PL2 + GPU TBP + RAM Typical + Storage Typical + Cooling Typical + Fans + System Overhead

Where:

  • CPU PL2: For Intel CPUs, we use PL2 (Maximum Turbo Power) from Intel ARK. For AMD CPUs, we use official TDP.
  • GPU TBP: Total Board Power (typical average draw under gaming load) from manufacturer specification and TechPowerUp databases.
  • RAM Typical: 5W to 16W depending on DDR4/DDR5 speed and stick count.
  • Storage: 3W to 10W per drive depending on SSD/HDD configuration.
  • Cooling: 5W for air coolers, up to 20W for custom loops with pumps.
  • Fans: 3W per case fan.
  • System Overhead: 15W default for motherboard chipset and motherboard LED overheads.

2. Transient Power Spike Modeling

Modern graphics cards and processors draw power in extremely brief, microsecond-duration spikes that exceed average limits. We model these peaks using multipliers sourced from Cybenetics PSU lab:

Transient Peak (W) = (CPU PL2 × 1.20) + (GPU TBP × Tier Multiplier) + Other Components

GPU Tier Multipliers used:

  • Budget Tier: 1.20× (e.g., RX 6600)
  • Mid-Range Tier: 1.35× (e.g., RTX 4070)
  • High-End Tier: 1.50× (e.g., RTX 4080 / RTX 5070)
  • Ultra / Halo Tier: 1.57× (e.g., RTX 5090)

The CPU transient multiplier is set to a constant 1.20× of its PL2 limit.

3. ATX 3.1 & 3.0 Compliance check

Under Intel's ATX 3.1 design guide, compliant power supplies are built to tolerate 200% of their rated output for up to 100 microseconds. Older ATX 2.x units do not guarantee this.

When checking compliance, we compare the calculated Transient Peak with the PSU's peak output tolerance:

  • ATX 3.1 / 3.0: Peak Tolerance = PSU Wattage × 2.0
  • ATX 2.x: Peak Tolerance = PSU Wattage × 1.3

If the system's Transient Peak exceeds the PSU's Peak Tolerance, the build is flagged as **Dangerous**.

4. 5-Year TCO & Efficiency Modeling

Annual electricity cost is calculated using local electricity rates, daily usage hours, and efficiency curves:

Annual cost = (Base Draw / Efficiency) × Hours × 365 × Rate

We pull CLEAResult 80 PLUS efficiency curves at 20%, 50%, and 100% load points for each certification tier (Bronze, Gold, Platinum, Titanium) to compute accurate wall-power draws depending on system load.

Data Sources & Citations

Every specification in our database is compiled and cross-referenced from:

  1. Intel Corporation: ATX 3.1 Design Guide Specification (Revision 2024).
  2. Cybenetics: PSU Efficiency & Noise Level Database, and Cybenetics Power Excursion Testing Standards.
  3. TechPowerUp: GPU Database specs and real-world oscilloscope testing summaries.
  4. NVIDIA & AMD: Official whitepapers and spec sheets for RTX and RX graphics cards.