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 desktop 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 — and it's a core reason why Slack is so slow on the desktop compared to lighter, native apps.
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 Slack battery drain grows proportionally.
Many people compensate by dimming their screen to stretch battery life, never realising the real culprit is the chat application quietly running in the background.
Why Slack drains your battery even when you're not using it
Does Slack drain your battery even when you're idle? Yes — because it keeps several processes running continuously, regardless of whether you're actively in the app:
- 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 is individually 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. This is also a key reason why Slack feels so slow on the desktop — the Electron shell never truly steps out of the way, which is especially noticeable if you're wondering why Slack is so slow on Mac.
Short-term fixes for Slack battery drain
- Quit Slack completely when you step away. Don't minimise 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 for a slow, battery-hungry Slack
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 the problem, and they don't address why Slack is so slow to start or so heavy when running alongside other apps.
A native Slack client that genuinely idles at near 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.