Gina Johnson
There are various factors that determine the power consumption of a sleeping Mac. The type of Mac, the number of apps running, and the length of time it sleeps for all play a role in the amount of power used. For example, a MacBook Pro M2 Max with Power Nap and network wakeup disabled consumes between 1W to 3W of power when sleeping. On the other hand, a MacBook Air consumes about 0.17% of its battery's full capacity per hour of sleep. Additionally, the settings and usage habits of the user can also impact power consumption. For instance, a Mac with external drives connected may experience issues when the computer goes to sleep. Ultimately, the power usage of a sleeping Mac varies depending on its specific characteristics and usage.
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What You'll Learn
Power Nap mode
Power Nap is a feature that allows Mac computers to stay up to date and perform administrative tasks while sleeping. It was introduced by Apple in 2012 alongside some Mac models running OS X Mountain Lion. Power Nap is only available on Intel-based Mac computers with SSD storage. The latest M1/M2 Macs with Apple silicon chips do not have or need Power Nap due to their "always-on" processor technology.
When a Mac with Power Nap is sleeping, it will periodically activate to update information. The specific tasks performed during Power Nap depend on whether the Mac is running on battery power or is plugged into a power adapter. When using battery power, Power Nap will perform low-energy duties such as receiving new Mail messages, updating Contacts, Reminders, and Photo streams. When plugged into a power adapter, Power Nap can handle more energy-intensive tasks, such as launching Time Machine to perform backups, indexing files in Spotlight, updating the Help Center, and downloading software updates.
Users can customise Power Nap settings on their Mac by going to the Apple Menu, selecting System Preferences, and then choosing Battery or Energy Saver. Here, they can choose to enable or disable Power Nap while on battery power or while plugged into a power adapter. Power Nap is designed to work without significantly impacting the device's battery life.
Overall, Power Nap is a useful feature for Mac users who want to keep their computers up to date and performing administrative tasks while sleeping, without worrying about excessive power consumption.
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Manual sleep vs. shut down
The choice between manually putting your Mac to sleep and shutting it down depends on your schedule and device usage. If you're stepping away from your Mac for a short period, sleep mode is ideal as it saves power and allows you to resume work instantly. However, if you're done using your Mac for the day, shutting it down is recommended to save energy and allow your device to rest and reset overnight.
Manual Sleep Mode
When you manually put your Mac to sleep, it enters a low-power mode. The non-essential hardware, such as the display and hard drive, powers down, while other components like the CPU continue to function in a low-power state. This helps minimise energy consumption. Additionally, a sleeping Mac can perform maintenance tasks, ensuring faster performance when you return to using it.
Sleep mode is perfect for short periods when you're not using your Mac. It allows for a swift wake-up process, as the current state of your device is stored in the RAM. This means you can instantly resume your work without any delays. Sleep mode is also beneficial if you want to transport your laptop quickly, as it doesn't require the vigilance of shutting it down.
However, some users have reported issues with their Macs waking up by themselves after being put to sleep. Additionally, sleep mode may not be as effective in reducing power consumption on newer Macs, and shutting down may be preferable for longer periods of inactivity.
Shut Down
Shutting down your Mac completely powers off all components, ensuring no power is being consumed. This can save energy, especially if you're not going to use your laptop for a day or two. Shutting down also clears the computer's RAM, removing any corrupt or junk data, and allows the device's components to cool down.
Regularly shutting down your Mac can help prevent minor issues and is recommended if you won't be using your device for an extended period. It's also advisable to shut down your Mac before transporting it over long distances, as it reduces the risk of damage to delicate moving parts.
However, shutting down and starting up a computer can consume more energy due to increased disk access and processor power. Additionally, the process takes longer than waking a sleeping Mac, and you'll need to close and reopen all your applications.
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Power usage when asleep
Depending on your settings and usage habits, your Mac may be wasting power when asleep. In Sleep mode, your Mac can perform a number of activities, including updating Mail, Calendar, Notes, iMessage, and other apps. Additionally, Find My will broadcast your Mac’s location, and if your Mac is connected to a power adapter, it can download updates from the Mac App Store, and Time Machine backups will run. Some third-party software can also wake a sleeping Mac to run. Disabling this setting can save power.
If you enable Wake for network access or Power Nap, your Mac can also share certain resources, such as a shared printer, or music from the Music app. A user can also connect to your Mac over a network and mount shared volumes; initiating a connection wakes the Mac, even if the display of a laptop is closed.
The amount of power used in Sleep mode varies. One source suggests that a MacBook Air consumes about 0.17% of its full battery capacity per hour. Another source states that a MacBook Pro consumes between 1W to 3W when sleeping, with Power Nap and network wakeup disabled. A third source suggests that a 2019 Retina 5k 27-inch Mac running Monterey draws 134W when asleep, which is a surprisingly high amount of power.
To save power, some users recommend shutting down your Mac instead of putting it to sleep, especially for overnight or long absences. This is because a Mac uses about .25 watts of power when it’s turned off but still plugged into an outlet, and the power used during the shutdown and startup processes may be less than the power used during Sleep mode over the same period. However, shutting down your Mac every night may not result in any power savings over sleep, depending on how many apps have to quit and reload. Additionally, modern Macs are usually ready for action within a few seconds of waking up, so the convenience of Sleep mode may outweigh the potential power savings of shutting down.
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Security concerns
When it comes to the security of a sleeping Mac, your level of concern should depend on the environment you're in. For example, at home or in the office, you may feel more at ease than when travelling and staying in a hotel room or passing through security checkpoints. Here are some security concerns and precautions to consider:
Physical Access by Attackers: If your Mac falls into the wrong hands, a skilled attacker who gains physical access to your sleeping device may be able to exfiltrate data or cover their tracks by eliminating any evidence of their intrusion. To mitigate this risk, it's advisable to keep your Mac within your sight and possession whenever possible, especially when travelling. However, be cautious at border crossings, as some countries may require you to surrender your device for inspections, potentially compromising your data privacy.
Network Vulnerabilities: Enabling "Wake for Network Access" on your Mac can introduce security risks. If your Mac is discovered on a network, an attacker could potentially exploit vulnerabilities, especially if you're not using the latest macOS version or have outdated software installed. Additionally, certain services like Screen Sharing, File Sharing, or Remote Login can provide remote access to malicious actors who have obtained your password through other means. To check if these services are enabled, navigate to System Settings > General > Sharing on macOS Ventura and later, or System Preferences > Sharing on older macOS versions.
Malware and Remote Awakening: Malware installed on your Mac could potentially awaken it from sleep mode, providing an opportunity for attackers to access your data. Additionally, if an attacker has targeted you specifically and gained your password, they may be able to remotely connect to your Mac if certain services are enabled.
Data Privacy in Less Trusted Environments: When in less trusted environments, such as hotel rooms or public spaces, it's advisable to shut down your Mac completely when not in use. This precaution reduces the risk of unauthorised access and potential data breaches, such as the "evil maid" scenario, where someone could attempt to access sensitive information on your device without your knowledge.
While sleeping Macs do offer some power-saving benefits, it's important to balance these considerations with the potential security implications outlined above. Staying vigilant and adopting appropriate security measures can help safeguard your data and privacy.
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How to put your Mac to sleep
When you're not using your Mac, you can save energy by putting it to sleep. When asleep, your Mac is turned on but consumes much less power. It takes less time to wake your Mac from sleep than it does to start it up after being turned off.
- On a Mac laptop, close the display.
- If you have the option on your keyboard, press Option-Command-Media Eject key.
- If your Mac has a Touch Bar, you can add the Sleep button to the Control Strip. First, go to the Apple menu, then System Settings, and click on Keyboard in the sidebar. Then, click on Touch Bar Settings, followed by Customize Control Strip, and finally, drag the Sleep button onto the Touch Bar.
- Press a key on the keyboard or click the mouse or trackpad. On a Mac laptop, simply open the display.
For security, you can set an option to require a password after waking your Mac. You can also set your Mac to wake for network access, allowing users to access shared services.
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Frequently asked questions
Yes, a sleeping Mac does use a small amount of power.
It depends on the model. A MacBook Air consumes 0.17% of its battery's full capacity per hour. A MacBook Pro consumes between 1W and 3W. A 2019 Retina 5K 27-inch iMac draws 134W when asleep.
You can put your Mac to sleep by choosing Sleep from the Apple menu, pressing the Power button for 1.5 seconds, or pressing Control-Shift-Eject (or Power, if your keyboard has that key).
When sleeping, a Mac can perform various tasks such as updating apps, broadcasting its location, and downloading updates and backups. These tasks require a small amount of power.
Shutting down your Mac can save a small amount of power, especially if you won't be using it for several days. However, the power savings may be negligible compared to sleep mode, and you'll need to factor in the power required for shutting down and starting up.
