Hello,

I will tell you this much. I made the mistake of buying two 40 cubic foot tanks. Its about $30 bucks to get refilled. For the 185 cubic foot (whatever the largest size is) that I bought is a little more than $40 to refill. So not difficult math to figure out. Thats almost 5 times more gas for 1/4 more in cost. With gas, as long as you close the main valve its not going anywhere. I went through those 40 cubic footers fast. So I ended up craigslisting the two 40 cubic foot tanks and got some of my money back. Your basicly paying for the energy it takes to bottle it up. Your gonna waist a lot of money with a smaller tank. One piece of good advice? Air/gas has sales every so often on tanks. I think payed $200 for the largest tank filled. I have welded for atleast 6 hours on it so far without it getting low. Though I know its getting close because of that pressure curve. Hope this helps