The fan noise is not a coincidence
If your laptop fan spins up shortly after opening Slack, that's Chromium — the browser engine bundled inside the app — doing background work. Chromium consumes CPU cycles; CPU cycles generate heat; heat triggers the fan; and the fan draws power from the battery.
A well-designed native application should idle at close to 0% CPU. Slack's official client typically runs at 1–5% even when you're not actively using it. That may sound small, but sustained over an eight-hour workday it adds up.
How much battery does Slack actually cost?
On a modern laptop, 2–5% sustained CPU usage translates to roughly 15–30 minutes of lost battery life per day — just from having Slack open. On older hardware or a battery that's already degraded, the impact grows proportionally.
Many people compensate by dimming their screen to stretch battery life, never realizing the real culprit is the chat application running in the background.
Why Slack uses CPU even when you're not in it
Slack keeps several processes running continuously, regardless of whether you're actively using it:
- Message polling: checking for new messages across every channel in every workspace
- Presence updates: continuously broadcasting your "active" or "away" status to Slack's servers
- Spell-check service: running passively in the background
- Crash telemetry: periodically collecting and transmitting diagnostic data
Each of these individually is small. Together, they prevent the CPU from reaching the low-power idle state that modern processors are designed to use when nothing important is happening.
Short-term fixes
- Quit Slack completely when you step away. Don't minimize to tray — quit it from the menu. This is the fastest and most effective thing you can do.
- Disable hardware acceleration (Preferences → Advanced). This eliminates the GPU process and reduces heat generation, often meaningfully.
- Reduce your workspaces. Each connected workspace adds background polling load. Sign out of ones you don't use actively.
- Use "Do Not Disturb" mode when you don't need notifications. It reduces some background activity.
The permanent fix
Slack drains your battery because of how it's built — it depends on a browser engine that wasn't designed for minimal background power consumption. The workarounds above help but don't fully solve it.
A native Slack client that genuinely idles at ~0% CPU doesn't have this problem. msga is built without Chromium. When you're not interacting with it, it uses effectively no CPU and allows your laptop's processor to drop to its lowest power state. Your fan stays quiet. Your battery lasts longer.