Check GPU workload on battery after adding a second monitor

Your laptop may feel slower on battery after you connect a second monitor, especially during games, video, or graphics work. The extra display can increase the work the computer does, and some laptops also change power settings when unplugged.

Use the Graphics Test to compare a repeatable browser graphics workload in each setup. It reports shading performance and fill rate at 1080p, with a score out of 100. It does not show the GPU's live workload percentage, power draw, or temperature.

Compare the graphics test results

1. Open the Graphics Test on the laptop you want to check.
2. With the second monitor connected, unplug the charger and let the laptop settle for a minute. Run the test and note the score, whether the test stutters, and the current battery level.
3. Run the test two more times in the same setup. Record each result, since short benchmark scores can vary with background activity.
4. Disconnect the second monitor and repeat the runs on battery. Keep the same browser, power mode, and approximate battery level. If you have a result from before adding the monitor, compare that too.

Do not run a heavy app, video stream, or download during the comparison. Close extra browser tabs and pause background tasks that you can safely pause. If your battery level drops substantially between sets, recharge and repeat, because the laptop may change its power behavior at low charge.

What the result means

The score is similar with one or two monitors

The browser graphics workload performs about the same in both setups. That is reassuring, but it does not prove every game or creative app will perform identically. Those programs may use a different graphics workload, resolution, or GPU.

The score drops only with the second monitor connected

The display setup is associated with a performance change, but the score alone cannot identify the cause. The second screen can add work for the graphics system, particularly at a high resolution or refresh rate. The operating system may also select a different graphics processor or apply a different power limit.

The score drops on battery in both setups

The laptop is likely limiting performance while unplugged, or the result may be affected by battery saver, heat, or background activity. Compare the same one-monitor test while plugged in. A higher plugged-in score points toward a power or thermal difference, not necessarily a fault in the second monitor.

The runs vary widely or stutter

A changing score can come from background work, heat, or a browser that is busy. Repeat the test after closing unnecessary apps and letting the laptop cool. For a broader look at performance with an external display, see how to check performance with an external display.

How to fix a drop in performance

1. Use the same power mode for both comparisons. In Windows 11, open Settings › System › Power & battery › Power mode and use the same available mode for each test. On a Mac laptop, check System Settings › Battery and keep Low Power Mode in the same state for both runs. Do not compare one setup in a power-saving mode with another in a performance mode.
2. Check the display resolution and refresh rate. In Windows 11, open Settings › System › Display, select each screen, and review its resolution and refresh rate. On a Mac, open System Settings › Displays and check the options for the built-in and external displays. If you are trying to isolate the effect of adding a screen, keep its settings consistent between tests.
3. Check battery saver and charge level. In Windows 11, go to Settings › System › Power & battery and check Battery saver. On a Mac, review System Settings › Battery. Repeat at a similar charge level, since power behavior can change as the battery gets low.
4. Give the laptop room to cool. Set it on a hard, flat surface and keep the vents clear. Let it cool for several minutes before repeating the test. If the score falls in later runs, heat may be limiting performance even if the fan is running.
5. Remove unnecessary background work. Pause large downloads, video playback, and demanding apps, then close extra tabs. Run each comparison in the same browser and avoid switching windows while the test runs.
6. Reconnect the display and restart the laptop. Check that the display cable and adapter are firmly connected, then restart and repeat the comparison. If the change began after connecting through a dock or adapter, test a direct connection if your laptop supports one.

What this browser test can and cannot tell you

The Graphics Test provides a repeatable graphics workload, not a live readout of how hard your GPU is working in another app. A lower score shows that this browser test completed less work in that run. It cannot report exact GPU utilization, temperature, power draw, or which component caused the change.

For practical work, check the application where you notice the slowdown as well. A game may render at your external monitor's native resolution, which can demand more graphics work than the test's 1080p workload. A video editor may rely more on decoding or effects. For a comparison of GPU types, see how to compare integrated and dedicated graphics.

Use the test results as a before-and-after comparison on the same laptop, not as a direct rating against a different computer.