Technical guide
PC Power Consumption Explained: Watts, kWh, PSU Ratings, and Wall Draw
Review watts, kWh, PSU rated output, conversion efficiency, and workload-dependent wall draw before interpreting the calculator result.
PC operating-cost utility
PC Electricity Cost Calculator
Estimate how much electricity a PC uses and what that energy costs from your own average wall-power estimate, daily usage time, and electricity price. No component power database or PSU-wattage guess is involved.
Interactive calculation
Enter your wall-power estimate
Use the PC's average AC power draw at the wall during the usage period you want to estimate. The default values are only an example starting point, not a claim about a typical PC or electricity tariff.
Do not enter the PSU's rated wattage. A 750 W or 850 W PSU rating describes output capacity; it does not mean the computer continuously draws that amount from the wall.
Currency selection only formats the result. No exchange-rate conversion is performed.
Estimated monthly electricity cost
$7.30
Based on the entered average wall draw and daily usage, not a measured device profile.
- Energy per day
- 1.2 kWh
- Average month
- 36.52 kWh
- Annual energy
- 438.29 kWh
- Estimated annual cost
- $87.66
Calendar assumption: the entered hours/day repeat across 365.2425 days/year. An average month uses 30.436875 days (365.2425 ÷ 12), not a silent 30-day shortcut.
What changes the real bill: your actual wall draw, idle/sleep time, workload mix, electricity tariff, taxes/fees, and whether monitors or other peripherals are included in the measured wattage.
Calculation basis
Power is not energy
Watts measure power at a moment in time. Electricity use over time is energy, commonly billed in kilowatt-hours. One kilowatt-hour is one kilowatt of power used for one hour.
The calculator converts the entered average wall draw from watts to kilowatts, multiplies it by the entered hours/day, and then scales that daily energy across 365.2425 days/year.
Monthly figures use an average calendar month of 30.436875 days, calculated as 365.2425 ÷ 12. Individual billing months still vary by calendar length and utility billing period.
PSU rating
Capacity is not wall consumption
A power supply's advertised wattage is its rated output capacity, not a statement that the PC continuously consumes that wattage. PSU efficiency also varies with load, so the most useful input here is measured or sensibly estimated AC power at the wall for the workload period you care about.
If your wall-power figure excludes a monitor, speakers, networking gear, or another peripheral, the estimate excludes those devices too. Keep the input boundary consistent with what you want to price.
References
Unit and PSU guidance
These sources support the unit definitions and the distinction between PSU rated capacity, load, and wall-side efficiency. They do not provide or imply a typical PC power draw for this calculator.
01 · U.S. Energy Information Administration
Measuring electricity: watts, watt-hours, and kilowatt-hours02 · NIST
Watt (W): unit of power03 · Intel
ATX power-supply efficiency versus load guidance
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