How many watts does a desktop computer use?
A desktop computer uses 150–400 W (about 250 W on average). Running 6 hours/day, that is about 1.50 kWh a day and 45.0 kWh a month — roughly $8.24 a month at the U.S. average rate of 18.31 ¢/kWh.
This is the desktop computer electricity usage reference: watts, amps on a 120 V circuit, the kWh math, and links to what that usage costs in each state.
Watts, amps, and kWh for a desktop computer
| Measure | Value |
|---|---|
| Rated wattage range | 150–400 W |
| Average draw used in our math | 250 W |
| Amps at 120 V | 1.3–3.3 A (2.1 A at the average draw) |
| kWh per hour | 0.25 kWh |
| kWh per day at 6 hours/day | 1.50 kWh |
| kWh per month | 45.0 kWh |
| Cost per month at the U.S. average (18.31 ¢/kWh) | $8.24 |
The math is kWh = watts × hours ÷ 1000 and amps = watts ÷ volts. A standard 120 V household circuit on a 15 A breaker carries about 1,800 W. For the dollars in your state, open cost to run a desktop computer in Texas and switch states from there.
Desktop Computer electricity usage profile
| Metric | Value |
|---|---|
| kWh per hour | 0.25 kWh |
| kWh per day (typical) | 1.50 kWh |
| kWh per month (typical) | 45.0 kWh |
| kWh per year (typical) | 547.5 kWh |
| Low runtime scenario | 3 hours/day |
| High runtime scenario | 9 hours/day |
Connect usage to cost tools
Related appliance usage pages
Source & Method
Source: U.S. Energy Information Administration (EIA) Retail Sales of Electricity. Last dataset period: July 2026. Usage calculations use fixed appliance wattage and runtime assumptions so results stay comparable across pages.
Frequently asked questions
How many watts does a desktop computer use?
A desktop computer uses 150–400 W (about 250 W on average). Our usage and cost math uses 250 watts running 6 hours/day.
How many amps does a desktop computer draw?
On a 120 V circuit, 150–400 W works out to about 1.3–3.3 A; at the 250 W we use in the math that is 2.1 A.
How much electricity does a desktop computer use per month?
About 45.0 kWh a month at 6 hours/day. Lighter use (3 hours/day) comes to roughly 22.5 kWh and heavier use (9 hours/day) roughly 67.5 kWh.
How much does it cost to run a desktop computer?
About $8.24 a month at the U.S. average rate of 18.31 ¢/kWh — from roughly $5.72 in Louisiana to $21.60 in Hawaii at the same usage. The state cost-to-run pages price it at every state's rate.