Does OLED Black Actually Save Power?

I recently bought a new laptop (Lenovo Yoga 7 if anyone's wondering) with an OLED screen. I chose one with an OLED screen because OLED screens actually turn off black pixels and dim darkly colored ones. Since I use everything in dark theme, I figured this would grant me some extra battery life. But does it?

In order to verify my theory I ran the following script in a tiny little terminal window:

watch -n 1 "cat /sys/class/power_supply/BAT1/power_now | awk '{print \$1/1000000 \" W\"}'"

I stopped all unnecessary processes and closed all windows to reveal my wallpaper, which is pure black. The only other thing visible was the small terminal window to monitor the power draw and another mini terminal window to edit my Hyprland configuration. When the background was pure black, the power draw stabilized at aroudn 5.3 Watts. Then I changed the background to pure white, and the power draw went up to a bit over 5.4 Watts. So not really much difference.

However, when I ran those tests, my screen brightness was quite low, because I was inside. So I maximized my brightness and ran the tests again. Here are the results:

Pure black: 5.3 W
Pure white: 9.6 W

Wow! That's a significant difference!

So if your OLED screen is low brightness, dark or light doesn't make a big difference. But if you're outside and you need a bright screen, dark mode can help extend your battery life.