he quotes time and power.
multiply that and you get the energy of the 15 MWh he sized the battery at.
now how much does this 15 MWh battery weigh is a interesting question.
now the wording might not be perfect but it's quite clear.
on the other hand people saying this windmill prodcues 1 MW per year now that is stupid.
oh and Translation:
"reading comprehension: not so good"