“Off” is not always off
Many devices with screens have several power states. A display that looks dark may be fully powered down, or it may be waiting for a signal, a remote command, a network message, or a touch. Each of those readiness features uses a little power. The amount is small compared with the display running at full brightness, but because it can continue for most hours of the year, it may add up.
The terms vary by product, but a rough ladder is common:
- Fully on. The picture is showing at normal brightness.
- Idle or dimmed. The screen is on but lowered in brightness, often after a period without input.
- Sleep or standby. The panel is off, but the electronics are partly awake so the device can respond quickly.
- Deep sleep or soft off. Almost everything is off, with only a small circuit watching for a wake-up event.
- Hard off. Unplugged or switched off at a physical switch, so the display draws nothing from the supply.
Quick-start features, network standby for casting or remote control, voice assistants, and scheduled updates tend to push a device toward the more awake states. Manufacturers describe their products’ modes in documentation, and regional rules often set limits on standby draw, which differ by place.
Why standby adds up
Consider a made-up example. Suppose a device in standby draws 1 watt around the clock. Over a day that is 24 watt-hours, and over a year of 365 days it is 8,760 watt-hours, or about 8.8 kilowatt-hours. That is small for one device. But a building with hundreds of screens would have hundreds of times that, and the figure keeps running whether anyone is using the equipment or not. The 1 watt value here is invented only to show the arithmetic; real standby levels vary widely and are often lower in newer designs.
Whether this matters depends on the setting. For a home with a few devices, standby is usually a minor part of total use. For organizations with many displays, such as offices, schools, or retail digital signage, scheduling screens to power down overnight can be a meaningful and easy change.
Always-on displays
Some devices, particularly phones, tablets, and wearables, offer an always-on mode: the screen shows a dim, limited image such as the time, date, and notifications even when the device is idle. Other uses include e-paper shelf labels, room signs, and low-power information panels.
How they keep the cost down
Several techniques make always-on operation practical:
- Showing very little. A mostly black image with a few bright elements lights only a small number of pixels. This works especially well on emissive screens where dark pixels draw almost nothing, as discussed in dark mode and power use.
- Lowering brightness. The always-on view is typically much dimmer than normal use.
- Reducing the refresh rate. If the content changes only once per minute, the panel does not need to update dozens of times per second. Some panels can drop to a very low rate when content is still, which reduces the work done by the display and its electronics.
- Using a separate low-power processor. The main processor can sleep while a small controller updates the display.
- Turning off when not useful. Sensors can detect that the device is face down, in a pocket, or in a dark room, and switch the display off. This overlaps with ambient light sensing.
- Using a reflective panel. E-paper displays need power mostly when the image changes, so they suit always-on content such as signs. See how e-paper displays hold an image without power.
What it costs
An always-on display uses more energy than a screen that is fully off, but how much more depends heavily on the panel type, brightness, content, and how often the image changes. For devices with batteries, the cost shows up as shorter time between charges. Manufacturers sometimes offer the feature as an option so users can choose. It is hard to give a single figure that would be true for all devices, and an exact number would not be meaningful without knowing the product.
There is also a wear consideration for emissive panels. Elements that stay lit for long periods can age faster than the rest, and designers often shift the position of the always-on image slightly or dim it to reduce this. Image retention on LCD and OLED screens describes the concern in more detail.
Standby in public and commercial displays
Large screens in public spaces may be left powered all day by default. Some have schedules, motion sensors, or network controls to turn them off or dim them. Doing so can save energy and reduce wear, but must be balanced against the need for screens to be ready when people arrive and the time they take to start up. Display decisions for digital signage and public space displays involve these trade-offs, and continuous operation covers the other end, where screens must run all the time.
Some professional displays also use standby to keep warm components stable or to allow remote management. Whether that is worthwhile depends on the application.
Practical steps
- Use sleep timers and auto-off settings that fit your use.
- For equipment you rarely use, consider a switched power strip or a physical switch, remembering that some devices may take longer to start or lose settings.
- Check the device’s own menu for options such as quick start, network standby, or always-on display, and consider whether you need them.
- In organizations, schedule displays to match opening hours where possible.
- Measure rather than guess. A plug-in power meter can show actual standby draw for a device, though safe use should follow the meter’s instructions.
Keeping perspective
Standby draw is usually small per device but persistent, while active use is larger but intermittent. Which one dominates depends on how many hours a screen is actually in use. The aim is not to eliminate every watt but to avoid waste that provides no benefit. For the larger picture, see our overview of display energy use and the cost of keeping screens running.