Watt-Hours are quite possibly the stupidest measurement of energy. „Oh let’s take a unit of joules per second and multiply it by a bunch of seconds. What do you think we get?“ Apparently not fucking joules.
And then applying SI prefixes to them? Absolutely perverse.
Joules, as is the international Standard. 1 W•h = 3.6 kJ. One of the issues with watt-hours is that they’re so unconventional a unit that people think they’re a rate of change (Watts over time - W/h) which would be a measure of the fluctuation in wattage or colloquially an acceleration of energy. You so often see people doing crazy broken math with them as a result.