Why the watt is the most important spec in battery-powered devices

> You can convert mAh to Wh, but only if you know the device’s voltage, which is another spec that’s often obscured.

If talking about Lithium battery, you need to multiple your Ah value by 3.3V and you can get your Wh. If talking about things like the chip's TDP - there are some problems of finding any metrics on a brand new laptop because the vendors try to do their chips as obfuscated as possible.