Pretty sure GP understands that, their point being you can't just wave away 'per unit time' when talking about it relative to generation, it matters.

"30kW per day" makes no sense. It's like saying "100km/h per day". W is a unit of power, Wh is a unit of energy.

It's unintuitive because a guy named Watt decided "Joule per second" is Watt, so the intuitive units Joule and Joule per second got turned on their head to W times hour and Watt. This is opposite to usual intuition of distance and speed for example, km and km/h. If I redefined the km/h to a "tick", then a km would become "tick times hour".

If you want a "better than nothing" but imperfect analogy, Wh is how much water you have in a bottle, and W is how quickly you can get the water out.

"30kWh per day" isn't waving away anything.

30kW is a rate.

30kWh is a measure of energy, about 100MJ.

30kWh/day is a rate again, 100MJ/day.

It seems clunky, but it's a way energy usage in a house is typically measured.