A typical desktop computer uses 100 to 800 watts while running, depending on the processor, graphics card, and what you're doing with it. A laptop uses 20 to 100 watts. The actual cost to your electric bill depends on your local electricity rate, how many hours per day you run the machine, and whether you leave it on constantly or shut it down between uses.
Key Takeaways
- Desktop computers draw between 100 and 800 watts during active use, while laptops typically draw 20 to 100 watts.
- A desktop running 8 hours daily costs roughly $15 to $60 per year in electricity, assuming an average U.S. rate of 14 cents per kilowatt-hour.
- Leaving a computer on 24/7 instead of shutting it down between uses can triple or quadruple your annual electricity cost for that machine.
- Gaming and video editing draw significantly more power than web browsing or word processing on the same computer.
- You can measure your own computer's power draw with a plug-in watt meter, which costs $15 to $30 and gives you exact numbers for your specific machine.
Why Computer Power Use Varies So Much
The wattage your computer draws is not fixed—it changes based on what the processor and graphics card are doing at any moment. When you are browsing the web or writing a document, your CPU and GPU are not working hard, so they draw less power. When you are gaming, editing video, or running a heavy calculation, those components work at full speed and draw much more.
A high-end gaming desktop with a powerful graphics card might draw 500 to 800 watts during intense use, while an older office desktop might draw only 100 to 150 watts doing the same task. A laptop is designed to run on battery power, so manufacturers build them to be efficient—they typically draw 20 to 100 watts, even under load. The power supply itself also matters: a newer, efficient power supply wastes less energy as heat than an older one.
Typical Power Draw by Computer Type
| Computer Type | Typical Power Draw (Watts) | Common Use Case |
|---|---|---|
| Budget desktop (web, email, documents) | 80–150 | Office work, browsing |
| Mid-range desktop (general use) | 150–300 | Photo editing, streaming, multitasking |
| Gaming desktop (active gaming) | 400–800 | Video games, 3D rendering |
| Laptop (general use) | 20–100 | Web, documents, light editing |
| Server or workstation | 300–1000+ | Professional rendering, data processing |
These numbers represent active use—the moment you are actually working or gaming. When a computer is idle (sitting at the desktop doing nothing), it draws less. When it is in sleep mode, it draws almost nothing. The difference between active and idle can be 50 to 200 watts on a desktop, which matters if you leave the machine running all day.
How to Calculate Your Annual Electricity Cost
To estimate what your computer costs to run, you need three pieces of information: the power draw in watts, the number of hours per day you use it, and your local electricity rate per kilowatt-hour. Your electric bill shows your rate—in the United States, it averages around 14 cents per kilowatt-hour, but it ranges from 10 cents in Louisiana to 22 cents in Massachusetts.
Here is the formula: (watts ÷ 1000) × hours per day × 365 days × your rate in dollars per kilowatt-hour = annual cost. For example, a 200-watt desktop running 8 hours a day at 14 cents per kilowatt-hour costs (200 ÷ 1000) × 8 × 365 × 0.14 = about $82 per year. A 50-watt laptop running the same schedule costs about $20 per year.
If you leave a computer on 24 hours a day instead of shutting it down, multiply the cost by three. That same 200-watt desktop running constantly would cost about $250 per year instead of $82. This is why turning off your computer when you are not using it makes a real difference on your electric bill.
Measuring Your Own Computer's Power Draw
The numbers above are estimates. Your actual computer might use more or less depending on its age, components, and how hard you push it. The most accurate way to know is to measure it yourself with a plug-in watt meter, also called a power meter or kill-a-watt meter. These devices cost $15 to $30, plug into the wall outlet, and show you the exact watts your computer is drawing in real time.
Plug the meter into the outlet, plug your computer's power cable into the meter, and turn the computer on. The meter will display the wattage. Open different programs—a web browser, a game, a video editor—and watch how the number changes. Run it for a few hours and the meter will also show you kilowatt-hours used, which you can multiply by your electricity rate to see the actual cost. This takes the guesswork out of your calculation and shows you which activities drain the most power.
When Computers Use the Most Power
Your computer draws peak power during specific moments. The highest draw usually happens when the CPU and GPU are both working hard at the same time—during gaming, 3D rendering, or video encoding. Streaming video uses moderate power. Browsing the web and word processing use the least. If you want to lower your electricity bill, the biggest impact comes from shutting down the computer entirely when you are not using it, rather than leaving it on idle.
Sleep mode is a middle ground. A computer in sleep mode draws only 1 to 10 watts, which is nearly nothing. If you step away for an hour, sleep mode saves more power than leaving it running idle. If you step away for the whole day, turning it off completely saves the most. Modern computers wake from sleep almost when ready, so there is no real penalty to using sleep mode during the day.
Comparing Desktop and Laptop Costs
A laptop costs significantly less to run than a desktop because it draws less power and is designed for efficiency. A typical laptop running 8 hours a day costs $15 to $30 per year in electricity. A typical desktop running the same schedule costs $40 to $100 per year. Over five years, that is a difference of $125 to $350 just in electricity. However, desktops often last longer and are easier to upgrade, so the total cost of ownership involves more than just power draw.
If you are choosing between a desktop and a laptop primarily for electricity cost, the laptop wins. If you already own a desktop, the cost to run it is usually not the deciding factor in whether to keep it or replace it—the cost is modest compared to the price of the machine itself.
Frequently Asked Questions
Does leaving a computer on all night use a lot of electricity?
It depends on the computer and your rate, but leaving a 200-watt desktop on for 8 hours costs roughly 22 cents. Over a month, that is $6 to $7 if you do it every night. If you do it every single night for a year, it adds $80 to $100 to your electric bill. Turning it off instead saves that money.
How much does it cost to run a gaming PC?
A gaming desktop drawing 500 watts and running 4 hours a day costs roughly $100 to $120 per year at average U.S. electricity rates. If you game 8 hours a day, double that to $200 to $240 per year. The exact cost depends on your specific graphics card, processor, and local electricity rate.
Do monitors use a lot of electricity?
Modern LCD monitors draw 20 to 60 watts, depending on size and brightness. An older CRT monitor drew more. A monitor running 8 hours a day costs $5 to $15 per year. Turning off the monitor when you step away saves more power than putting the computer to sleep, since the monitor uses a separate circuit.
Is it cheaper to leave a computer on or turn it off and on repeatedly?
Turning it off is always cheaper. The power surge when a computer starts up is brief and uses negligible energy. The cost of leaving it running idle for even a few hours exceeds the cost of that startup surge many times over. Modern computers are designed to handle frequent on-off cycles without damage.
Can I reduce my computer's power draw?
Yes. Lower the screen brightness, close unnecessary programs, use sleep mode instead of leaving it idle, and shut it down when you are done for the day. Upgrading to a newer, more efficient computer also reduces power draw, but the savings take years to recoup the cost of the new machine.