99.9% purity, 500ml/min, 4 atmosphere. [1].
At 4 atmospheres, can fill a 1000 gallon propane tank - in 4 days. At 1 atmosphere - one day!
$3500 of generators (same as above but at $700/unit) gets us 1.5 kWhr of usable storage with a generator. That is the same cost as a 20kW new battery bank - which can last 10 years in off-grid apps. We are a factor of 13x higher capital cost than batteries at this stage - which can be solved only by reducing cost of hydrogen generation equipment.
Ideal conditions - 40kWhr to generate 1 kg of hydrogen - [2]
Look at basic capital cost from last link:

For sensemaking - $1-5k capital costs per kW electrolyzer. A 1 kW electrolyzer -

Hydrogen Gas Generator

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