A/B Testing PC Power Supply (Monthly) Calculator
Compare the estimated monthly electricity use and cost of two PC power supply and usage scenarios.
Overview
Compare the monthly power cost of two PC power supply scenarios by entering each setup's typical component load, PSU efficiency, daily use, and your electricity price per kWh. This can help compare a more efficient power supply, different hardware loads, or different usage patterns.
How it works
The calculator estimates power drawn from the wall by dividing the PC's component load by the PSU efficiency. For example, a 350 W component load supplied at 85% efficiency needs about 412 W from the wall. It multiplies that wall power by daily hours and days per month to calculate kWh, then multiplies kWh by your electricity price. The comparison uses the same method for both scenarios.
How to use this calculator
- 1Enter the typical component power draw for Scenario A.
- 2Add the estimated PSU efficiency and daily use time for Scenario A.
- 3Enter the corresponding load, efficiency, and use time for Scenario B.
- 4Set your electricity price per kWh and the number of days to estimate.
- 5Review both monthly costs, energy use, and the potential cost gap.
Example Calculation
Scenario A average PC load
350
Scenario A PSU efficiency
85%
Scenario A use per day
6
Scenario B average PC load
350
Scenario B PSU efficiency
92%
Scenario B use per day
6
Electricity price
$0
Days per month
30
Scenario A monthly cost
$13.34
With the same 350 W component load used for 6 hours a day, Scenario A uses about 74.1 kWh and costs about 13.34 per month. Scenario B uses about 68.5 kWh and costs about 12.33 per month, a difference of about 1.01 per month.
Frequently asked questions
What PC power value should I enter?
Enter the average power used by your PC components during the period you want to model. A plug-in power meter can provide a more representative reading, but if you use a wall-power reading, set PSU efficiency to 100% to avoid counting efficiency losses twice.
Does a higher PSU wattage rating increase electricity use?
Not by itself. A PSU's wattage rating is its maximum capacity. Electricity use is mainly driven by the PC's actual load and the PSU's efficiency at that load.
Why does PSU efficiency affect monthly cost?
An inefficient PSU loses more energy as heat while converting wall AC power to the DC power used by PC components. A more efficient unit can draw less electricity for the same component load.
Does this include a monitor and peripherals?
No. Add their estimated power to the component load if you want a broader setup estimate, or calculate them separately.
How can I find my electricity price per kWh?
Check your electricity bill, provider account, or tariff information. If pricing varies by time of day, use a weighted average rate for your typical PC usage period.
Are monthly results exact?
No. PC load changes between idle, work, gaming, and other tasks, and PSU efficiency also varies with load. The result is best used as a comparison estimate.
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Assumptions and warnings
Assumptions
- The average component load represents the PC's typical DC power demand during the entered daily usage time.
- Power supply efficiency is treated as constant, although actual efficiency changes with load, temperature, and power supply design.
- The electricity rate is assumed to remain the same throughout the selected month.
- The estimate excludes monitor power, external devices, standby use, and other household electricity charges unless they are included in the entered load.
Warnings
- This calculator provides an electricity-cost estimate only; actual usage and electricity bills can differ.
- Use your electricity bill or tariff details for the most relevant unit rate, including any time-of-use pricing where applicable.