How many watts does a desktop computer use?
A desktop computer uses 4–385 watts while running, which is 0.03–3.2 amps at 120 V.
Desktop computer watts, amps and circuit
| Running watts | 4–385 W |
|---|---|
| Voltage | 120 V |
| Running amps | 0.03–3.2 A |
| Circuit | standard 120 V outlet |
Also called: computer, desktop pc, personal computer, desktop.
Desktop computer watts by size and type
| Size or type | Running watts, W | Volts, V | Amps, A | Starting watts, W |
|---|---|---|---|---|
| Desktop computer | 4–385 | 120 | 0.03–3.2 | — |
| Mini desktop (Mac mini), idle to full load | 4–145 | 120 | 0.03–1.2 | — |
| All-in-one (24-inch iMac), idle to full load | 40–105 | 120 | 0.33–0.88 | — |
| Workstation (Mac Studio, Mac Pro), idle to full load | 6–385 | 120 | 0.05–3.2 | — |
What size generator runs a desktop computer?
A desktop computer needs a generator that supplies at least 385 running watts. A 2,000 W generator covers it with its running rating alone; add the watts of anything else you run at the same time.
How long a portable power station runs a desktop computer
| Battery capacity, Wh | At 385 W, h | At 4 W, h |
|---|---|---|
| 500 | 1.1 | 106.3 |
| 1,000 | 2.2 | 212.5 |
| 2,000 | 4.4 | 425 |
| 3,600 | 7.9 | 765 |
A 500 Wh portable power station runs a desktop computer drawing 385 W for about 1.1 hours at 85% inverter efficiency. Runtime = capacity × 85% ÷ watts; the 85% efficiency is an assumption. The power station's AC output must be at least 385 W.
What it costs to run a desktop computer
Running a desktop computer at 195 W, the middle of its 4–385 W range, for one hour a day uses 71.2 kWh a year. That costs about $13 a year at $0.18 per kWh, the US average residential price for August 2026.
Your bill's total ÷ kWh used. 0.18 is the US residential average.
- Per day
- $0.04
- Per year
- $13
- Energy per day
- 0.2 kWh
- Energy per month
- 5.9 kWh
How it is calculated
- kWh per day = 195 W × 1 h ÷ 1,000 = 0.195
- Per month = 0.195 kWh × 30.4 days × $0.18 = $1.07
What affects desktop computer power use
The processor and graphics chips set the draw, and both change with the workload. The ranges are wall measurements published by the maker, from idle with only the desktop open to a test that keeps the processor fully busy. Light office work and browsing stay near the low end and far below the power supply rating. The figures do not include a separate monitor; an all-in-one includes its screen.
How the amps are calculated
Amps = watts ÷ volts. For 385 W at 120 V that is 3.2 A. The 4–385 W range covers typical models; the nameplate on a desktop computer gives the exact figure.