Instruction: Answer the given question by extracting information from the supporting document.

Input:
Question: What size tank do I need with this heater? How long will a 20 pound tank last?
Document: In my area it costs $17 to refill a 20 pound tank, so the cost to heat wit the LP system is a little lower than running my old heater on highway diesel, which burned as clean as K1 and does cost much less than k1.I gave it 4 stars rather than 5 because there are 3 improvements that would make it better in my opinion. The biggest would be to use a different outer coating on the LP hose.
I bought this product to unfreeze people's RV water pipes under their travel trailers, 5th wheels and motor homes. It sits low to the ground and has a long hose so that you can move it around, without having to move the tank!I charge $20 for my propane and time and it took a max of about 30 minutes to unfreeze everyone I helped.
I bought this heater and hooked it up to 30lb tank. I've only used it twice this winter, but it worked fine, heating my open frame 2-story garage to a relatively comfortable level while only on the low setting. that 30 degree rise in temp took about an hour to attain. I was able to work without freezing. My garage is NOT insulated and the outside temp was about 15 degrees before I started the heater. The garage inside temp was about 20 degrees prior to firing up the heater.
Couldn't be happier with this heater it heaters up the room or where ever you may need it I use it at work in my garage and it's amazing how warm it gets when it's negative out side for the price I recommend this 100% satisfied with my buy works great
I would have given this four stars but you have to hold the ignition button dowwn for a long time to start the heater. The high and low output is nice to have allowing you tailor the heat output.
this heater works great bought this size wanted enough heat this heater pumps out so much heat I have to keep turning it off when in was zero out.to bad it did not have a lower setting than it does.
Of course in cold weather is the only time I use it.My 2nd complaint is the 10 inch long power cord, which is mounted at the very bottom and is also very stiff when cold. It is a pain for an old man with a bad back to reach and plug in.3rd, and probably least of my complaints is the angle of the heater.
You have to lower it a little before tightening to make it stay. What is more of a problem for me, since I work on old machinery is if I need the heat closer to the floor I have to put a board under the rear to get the heat low enough to make it useable.None of these problems are big enough to make me regret buying it though, I still like the heater
Works great - starts easy. Best of all it has no obnoxious smell like my old kerosene heater had.I just use it to take the chill off in my shop in the mornings for about 20 minutes. Once I get working I shut it off. I've only been using it for a couple weeks so I don't know about its durability. Otherwise would have given 5 stars.
Have been using it now for several months and it still works great. Heats up quickly however if you crank it up it does go through a 20lb propane tank in about half the expected usage time. On low it's good for about 12 hours. Nice heater...very little emissions if any at all.
Answer: 40 lb tank works much better as the 20 lb tank can freeze up if you run it continuously.