What a live wallpaper actually costs your battery

Battery cost is not a property of an app; it is work multiplied by time. A wallpaper does very little work per frame but runs for the entire session, so the question that decides everything is *how many hours is it actually decoding?*

What draws power on a Mac

• •Display backlight — normally the single largest consumer. Brightness beats every software setting.
• •CPU — expensive per unit of work, especially sustained load on performance cores.
• •GPU — cheap for compositing, expensive for real-time rendering.
• •Media engine — extremely efficient for video decode. This is the path a good wallpaper uses.
• •Radios and disk — network and storage activity, unrelated to wallpaper except while downloading one.

Reading Energy Impact honestly

macOS reports Energy Impact in Activity Monitor — a relative score combining CPU time, wakeups, GPU use, and idle behaviour. It is not watts. Use it to compare apps on your own Mac, not to compare numbers between machines. Averaged over several minutes it is a good signal; a single snapshot is noise.

Why pause rules dominate

Suppose an efficiently decoded 4K loop costs a small fraction of a percent of CPU. Over eight unplugged hours that is still eight hours of *something*. Now add pause-on-battery: the wallpaper stops the moment you unplug and the cost goes to zero. Pause-in-full-screen removes the hours you spend in a full screen editor or a call. Display sleep removes the rest. Real-world battery impact is decided by these rules, not by shaving a megabit off the bitrate.

Measure it on your own Mac

1. Unplug and note the battery percentage and time.
2. Work normally for an hour with the wallpaper playing, then note the percentage again.
3. Repeat the same hour of work with the wallpaper paused.
4. Compare. If the difference is inside normal variance, the wallpaper is not your battery problem.
5. For a per-app view, check Energy Impact in Activity Monitor's Energy tab over a few minutes.

If you want the longest runtime

• •Turn on pause on battery — the single most effective setting.
• •Mirror one loop across displays instead of decoding several.
• •Prefer 24–30 fps loops encoded in a hardware-decoded codec.
• •Let Low Power Mode pause playback along with everything else.
• •Then lower your screen brightness, which will save more than all of the above combined.

MacWall ships these rules on by default; each one is documented in performance and battery.