I think you're pretty much putting words in his mouth. He didn't say a single word about energy balance. He just said "burning water", which is badly formulated

I think you're pretty much putting words in his mouth. He didn't say a single word about energy balance. He just said "burning water", which is badly formulated and unclear, but does not exclude using an external energy source for the hydrolysis. That energy could come from solar panels as you mentioned, with the drawbacks you mentioned. But it looks to be a good enough method.