Technology & Computing
PSU Wattage & 80 Plus Efficiency Calculator
Calculate AC power draw from the wall and headroom given a system's DC load and PSU's 80 Plus efficiency tier.
Your inputs
Change any value to update the result instantly.
AC power drawn from wall
444.4444 W
Power wasted as heat
44.4444 W
PSU load
53.3333%
Headroom remaining
46.6667%
Efficiency tier
90%
PSUs run most efficiently around 40–60% load; very low or near-100% load reduces efficiency and lifespan.
Formula and working
AC draw = DC load ÷ efficiency; Headroom % = (PSU rated wattage − DC load) ÷ PSU rated wattage
- 1
Collect the inputs
System DC load (watts) = 400 W; 80 Plus efficiency tier (typical load) = 90; PSU rated wattage = 750 W
- 2
Apply the formula
AC draw = DC load ÷ efficiency; Headroom % = (PSU rated wattage − DC load) ÷ PSU rated wattage
- 3
Result
AC power drawn from wall = 444.4444 W
Frequently asked questions
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
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