I once bought a refillable Propane kit and fitted to my motorhome, or as the US call it RV. to provide the cooking and heating. Once fitted it was checked by a qualified gas engineer and given a safety certificate. To fill, I would pull into a `gas` station that sold propane for vehicles, and just fill it up. There was a device in the tank to stop filling above the maximum allowed. The system had a contents gauge. If I had a need for propane now, I think I would consider buying another kit and have it so arranged I could pick it up when empty and take it too the nearest `gas` station to refill. At the time when I bought the system, I worked out the cost, and after filling the tank 4 times, it would be in profit over buying refilled cylinders from agents.