Why a device that is off still uses power
Many gadgets are never fully off. When you press the power button on a television, a games console or a printer, you often put it into standby rather than turning it off. In standby, parts of the device stay powered so it can respond to a remote control, keep a clock running, hold a network connection, receive software updates or start up quickly.
Even devices that look completely dead can draw a small amount of power. A common reason is the power supply. Chargers and adapters convert mains electricity to a lower voltage, and some draw a little current even when nothing is connected. These small, constant draws are often called phantom loads or vampire loads.
Regulations in many places limit how much power new products can draw in standby, so newer devices are often better than older ones. Even so, it is common for a home to have a lot of devices with some residual draw.
Why small numbers matter
Standby power is usually measured in watts, and it is easy to dismiss a few watts as trivial. The catch is time. A device left in standby draws power for the whole day, every day.
A simple worked example shows how this adds up. Suppose a device uses 10 watts in standby all the time:
- 10 watts for 24 hours is 240 watt-hours, or 0.24 kilowatt-hours, per day.
- Over a year of 365 days, that is 0.24 × 365 = 87.6 kilowatt-hours.
Multiplying that by your electricity price gives a rough yearly cost, and the figure is not huge for one device. Many households have several, though, and some devices draw more than others. The picture depends on the devices you have, so measuring beats guessing. Overall, standby is part of home energy use, but it is rarely the largest part. Heating, hot water and cooking often matter more.
How to find the devices worth acting on
Use a plug-in power meter. Inexpensive plug-in meters show the watts drawn by whatever is connected. Check your television, set-top box, console, printer, computer and its accessories. Some libraries and community groups lend these, which can save you buying one.
Do a night-time check. Switch off everything you can, then look at your energy meter readings when nothing seems to be running. If the meter keeps moving or the display shows a notable draw, something is still using power. Turning off sets of devices one at a time can narrow it down. Remember that fridges, freezers, routers and alarms may account for part of the base load.
Look for clues. Warm chargers, glowing lights, displays and standby LEDs often indicate a draw. A warm power brick is a hint of waste, although not proof of high consumption.
Check settings. Many devices have a quick start or instant-on mode which keeps them in a higher power state. Switching to an energy-saving mode, if you can live with a slightly longer start-up, often reduces the draw without any unplugging.
What is worth switching off
Not everything benefits equally. As a general guide:
- Often worth switching off: entertainment systems, games consoles set to instant-on, printers, spare monitors, desktop computer accessories and old devices with large power supplies. A power strip with a switch makes it easy to turn off a group in one go.
- Often not worth bothering with: devices that use very little, are awkward to reach or lose useful settings each time they are disconnected.
- Best left on: fridges and freezers, medical equipment, security or fire alarms, and anything where interruption could cause problems or lose data. If in doubt, check the manual rather than assuming.
- Think twice: your broadband router is often left on for convenience and for connected devices, and heating controls may need continuous power to keep schedules. Switching these off could cause more bother than benefit.
Automation and its trade-offs
Smart plugs and timers can switch devices off automatically, which helps if you tend to forget. They do use some power themselves, though, so they make most sense for devices with a clear standby draw, not for ones that use little. The same applies to many smart home devices, where the convenience and the energy cost of the control equipment should be weighed against the savings. A basic switched power strip does the job at no running cost.
Safety matters here. Do not overload sockets, avoid chaining extension leads together, and do not cover warm chargers or adapters. Follow the manufacturer’s instructions for heating appliances, and do not use a timer to start one unattended unless it is designed for that.
The wider picture
Cutting standby power is a good low-effort habit, but it should not distract from bigger items. It is also worth remembering that the carbon cost of each kilowatt-hour depends on the electricity grid where you live and the time of day, so the impact varies. Pair this with heating, hot water and appliance habits for a more complete picture, and replace old devices only when it makes sense, since discarded electronics add to electronic waste.