OK, the capacity of propane side.
Using 36.4 CF to 1 gal of liquid propane (from Google)
And using ghost307s 5141 SCF of natural gas (gas is gas??)

A 1000 gal propane storage tank (hopefully allowed by local laws)
36,400 CF of propane gas
7 hours of runtime +/-

The above is based on the sources mentioned.


John