The efficiency of hydrogen electrolysis seems low, but potentially not an issue if the absolute cost of wind/solar continues to drop - and it's a storage solution for smoothing renewable production too.
This is underappreciated.
Why are heat pumps not plausible? You can get them today.
https://piperepair.co.uk/2020/08/04/pipe-replacements-to-cut...
Aside from the cost (which might come down), heat pumps have some inherent disadvantages - reliance on insulation, and slow ramp up time. So no more opening the windows at night for fresh air, then getting the house back up to temperature in the morning.
Random note: I'm all for heat pumps & all for hydrogen. They just aren't for the same use cases. Heat pumps are good for heating+cooling of spaces. Hydrogen is good way to store electricity when care about energy-to-weight and/or need quick fuelling.
https://piperepair.co.uk/2020/08/04/pipe-replacements-to-cut...