The short answer: turn it off when you step away for more than an hour
Modern monitors use very little power when idle, so leaving one on overnight or for a few hours costs almost nothing. But turning it off when you know you will not use it for an hour or more saves electricity and extends the monitor's lifespan slightly. The real benefit is not the power bill — it is that you avoid unnecessary wear on the backlight, which is the part that fails first.
If your monitor has an automatic sleep mode, you can set it to power down after 15 or 30 minutes of no activity, which handles this decision for you. Most people find this the easiest approach because you do not have to remember to switch anything off manually.
Key Takeaways
- Turning off a monitor saves almost no money on your electricity bill, but it does reduce wear on the backlight, which typically lasts 30,000 to 60,000 hours before dimming noticeably.
- Sleep mode is the simplest option — set your monitor to power down after 15 to 30 minutes of inactivity, and it will do the work without you thinking about it.
- Turning a monitor on and off repeatedly throughout the day does not harm it; modern displays are designed to handle frequent switching.
- If you step away for less than an hour, leaving the monitor on makes no practical difference to cost or lifespan.
How monitor backlights wear out over time
Every monitor has a backlight — usually an LED panel or array of LEDs behind the screen — that produces the light you see. This backlight has a rated lifespan, typically between 30,000 and 60,000 hours. After that many hours of use, the backlight does not fail suddenly; instead, it gradually becomes dimmer, usually losing about half its brightness by the end of its rated life.
Turning the monitor off when you are not using it straightforward reduces the total hours the backlight runs. If you use your monitor eight hours a day and turn it off during breaks, you might add a year or two to the time before you notice dimming. If you leave it on 24 hours a day, you will reach that dimming point faster. The difference is real but modest — not something that will force you to replace the monitor next year instead of in five years.
The backlight is also the most expensive part to replace if it fails, so extending its life has some value. But most people replace their monitors for other reasons — a better resolution becomes available, they want a larger screen, or they upgrade their whole setup — before the backlight actually dims enough to bother them.
Sleep mode versus powering off completely
Sleep mode is when your monitor stays plugged in and powered on, but the screen goes dark and the backlight turns off after a set time of no activity. The monitor is still drawing a tiny amount of power — usually less than one watt — to watch for keyboard or mouse movement. When you move the mouse or press a key, the monitor wakes up in a second or two.
Powering off completely means pressing the power button or unplugging the monitor. The monitor draws almost no power and the backlight is completely off. The tradeoff is that it takes a few seconds longer to turn back on, and you have to remember to do it manually.
For most people, sleep mode is the better choice. You can set it in your operating system — Windows, Mac, or Linux all have display power settings — and then forget about it. Your monitor will handle the timing automatically. If you want to power off completely, you can still do that, but sleep mode removes the need to think about it.
The cost of leaving your monitor on all the time
A typical monitor uses between 20 and 60 watts when the screen is on, depending on the size and brightness. If you leave a 40-watt monitor on 24 hours a day for a year, that is about 350 kilowatt-hours of electricity. At an average US rate of 12 cents per kilowatt-hour, that costs roughly $42 per year.
If you turn the monitor off for eight hours a day — say, overnight — you cut that cost to about $28 per year. The savings are real but small. If you use sleep mode instead, which draws about one watt when idle, the cost difference is even smaller. The main reason to turn off your monitor is not the money; it is the wear on the backlight.
If you are concerned about power use for environmental reasons, turning off the monitor is a reasonable step. But it will not dramatically lower your electricity bill. The bigger power draws in most homes come from heating, cooling, and water heating.
Turning the monitor on and off frequently does not damage it
You might worry that switching a monitor on and off many times a day will wear it out faster. This is not how modern monitors work. The components that fail — the backlight, the power supply, the capacitors — are not damaged by being switched on and off. They are damaged by running continuously for thousands of hours.
Turning your monitor off and on ten times a day will not shorten its life. The only wear that matters is the total number of hours the backlight runs. So if you want to turn your monitor off every time you step away for 20 minutes, you can do that without worry. The monitor is designed to handle it.
The one exception is very old CRT monitors — the heavy, boxy kind from the 1990s and early 2000s — which could be stressed by frequent power cycling. But those are rarely in use anymore, and the same logic applies: the backlight (or in that case, the electron gun) wears out from running time, not from being switched on and off.
How to set up automatic sleep mode on your computer
On Windows: Open Settings, go to System, then Display. Scroll down to "Screen timeout" and set it to 15 or 30 minutes. You can set different timeouts for when you are plugged in versus on battery. The monitor will go dark after that time of no keyboard or mouse activity.
On Mac: Open System Settings, go to General, then click Lock Screen. Set "Turn display off after" to your preferred time — 15 or 30 minutes is typical. You can also set a separate timeout for when the Mac is sleeping.
On Linux: The method depends on your desktop environment. In GNOME, open Settings, go to Power, and set "Screen Blank" to your preferred time. In KDE, go to System Settings, then Power Management, and set the display timeout there.
Once you set this up, you do not have to think about it again. Your monitor will power down automatically whenever you step away, and it will wake up the moment you touch the keyboard or mouse.
When you might want to leave your monitor on
There are a few situations where leaving your monitor on makes sense. If you are actively using your computer — working, watching video, or gaming — turning it off between short breaks is unnecessary. Sleep mode will handle it for you anyway.
If you are running a long process that you are monitoring — a file transfer, a video render, or a software installation — you might want to keep the monitor on so you can see progress without moving the mouse. In this case, you can temporarily disable sleep mode, or just let the monitor go dark and move the mouse when you need to check on things.
If your monitor is very old and the backlight is already dim, turning it off will not help much. The backlight is already near the end of its life, and the small amount of additional wear from leaving it on for a few more months will not matter. At that point, the monitor is due for replacement anyway.
Frequently Asked Questions
Does turning my monitor off save money on my electric bill?
Yes, but the amount is small. Leaving a typical monitor on 24 hours a day costs roughly $40 to $50 per year in electricity. Turning it off for eight hours a day saves about $15 per year. Sleep mode saves almost as much as turning it off completely, with the advantage that you do not have to remember to do it manually.
Will my monitor last longer if I turn it off every night?
Yes, slightly. The backlight wears out based on total running hours, so turning it off overnight reduces wear. You might add a year or two to the monitor's useful life. But most people replace their monitors for other reasons before the backlight dims enough to notice.
Is it bad to leave my monitor on all the time?
It is not dangerous or harmful to the monitor itself, but it does accelerate wear on the backlight. The monitor will still work fine; it will just become noticeably dimmer sooner. For most uses, this is not a practical concern unless you plan to keep the same monitor for many years.
Can I damage my monitor by turning it on and off frequently?
No. Modern monitors are designed to handle frequent power cycling. The only wear that matters is the total number of hours the backlight runs, not how many times you switch it on and off. You can safely turn your monitor off and on as many times as you want throughout the day.
What is the difference between sleep mode and turning the monitor off?
Sleep mode keeps the monitor powered on but turns off the backlight after a set time of inactivity. It draws about one watt and wakes up when ready when you move the mouse. Turning it off completely draws almost no power but takes a few seconds to power back on and requires you to remember to do it manually.