"Very low efficiency"?

Without context, that is meaningless. Efficiency is something very dependent on context. This is something you would know, if you knew anything about efficiency.

1 kg of hydrogen produced using sunlight, is 33KWhrs of heat energy removed from the energy of the sun landing on Earth, regardless of efficiency.

That is 33KWhr less heat energy applied to the thermal mass of the planet, right?

A single solar powered 2.4kW electrolyser does that every 24hrs.

Which part of that do you think is affected by efficiency?

I will tell you - none.