How Many Gallons Are in a 30-lb RV Propane Tank?

A 30-lb RV propane tank is the beating heart of many fifth wheels, along with the occasional travel trailer. And that’s great if that were all there was to it. However, people throw around the terms “gallons” and “pounds” quite a bit. So how many gallons are in a 30-lb propane tank? Many websites claim the answer is 7.1 gallons but the answer is really 5.7 gallons. But why is that and what does that mean to you?

If you’re the proud new owner of an RV that’s rocking some 30-lb propane tanks, you may be curious as to what that means in gallons. It’s a good idea to keep up with both gallons and pounds because of their interchangeable use when describing them.

This article is for the 30-lb RV propane tank owners that want to know more about how their propane tanks function, especially in terms of longevity and application. We’ll walk you through the ins and outs of the propane world and show you how to convert pounds to gallons, vice versa, and much more.

How Many Gallons Are in a 30-lb Propane Tank?

On average, 7.13 gallons of propane will completely fill a 30-lb RV propane tank. However, propane expands while sitting inside the tank, so there has to be room to allow it to do so.

To allow for that expansion, propane companies only fill them up to around 80% capacity. Otherwise, it’s a serious safety issue. That means the 30-lb tank you just filled up is only filled to 80% or 24 lbs and that means you are getting 5.712 gallons of propane instead of 7.13 gallons.

Here’s The Math

1 gallon of propane weighs 4.2 lbs
1 lb of propane= 0.238 gallons
80% of 30 lbs= 24 lbs
Therefore: 24 lbs x 0.238 gallons = 5.712 gallons (or rounded up to 5.7 gallons)

How Much Does a 30-lb Propane Tank Weigh?

An empty 30-lb propane tank weighs about 25 lbs. And the propane itself weighs about 24 lbs when the tank is filled to 80% capacity. So the combined weight of the empty tank plus the propane filled to 80% capacity is about 49 lbs.

Depending on the type of 30-lb tank, that number may fluctuate a little. The empty tank weight varies by manufacturer and the type or gauge of steel they use in the construction of the propane tanks.

How Many BTUs are in a 30-lb Propane Tank?

The BTU capacity of one gallon of propane is 91,500 BTUs. The BTU is to a propane tank what amperage is to a battery. It’s the power behind the curtain. BTUs stands for British Thermal Unit, and it’s a measurement of power or, in this case, the heating content of the tank.

What it does mean is if you ran your RV propane tank at max capacity, you would burn roughly 91,500 BTUs an hour (number of BTUs in a gallon) and run out of propane in about 5.7 hours. Since you almost never need to burn through your propane that fast, a 30-lb propane tank will last for some time.

That’s why it’s a good idea to check the BTUs on any devices you’ll be using throughout the year. It will give you a solid estimate of how many propane tanks you might want to bring along, assuming you have the storage capacity.

How Long Will a 30-lb Propane Tank Last in the Winter or Summer?

It’s hard to say how long a 30-lb propane tank will last in the winter or summer because it really depends on what you use it for and for how long. Some full-timers get two weeks out of a tank, and some can burn through a 30-lb tank in a single week.

Many RVs have two 30-lb tanks with an automatic switchover when one of them runs empty. If you’re on shore power, you may not need it all that much. It also depends on where you’re located. If you head down to the Miami, Florida, area in the winter, you won’t need to use your RV’s propane furnace too much.

Minnesota in the summer is a fine idea if you want to cool off without running the A/C constantly. In general, you should only have to fill your tanks a couple of times at most during the summer. In the winter, maybe an extra trip to fill the tanks is necessary from time to time.

Solar panels, types of appliances, size of RVs, shore power or no shore power, your personal comforts, and, more importantly, you and your significant other’s personal comforts, all make a difference.

Which Travel Trailers Use 30-lb Propane Tanks?

Mostly fifth wheels and large travel trailers use 30-lb propane tanks. That’s not to say you couldn’t mount one on a front rack for a teardrop, but that’s an aftermarket upgrade. Small towables and travel trailers sometimes come with one or two 20-lb RV propane tanks.

Class A motorhomes typically have larger propane tanks that manufacturers build into the rig. However, Class B and C motorhomes often come with removable 20 or 30-lb propane tanks, but it just depends on the model/manufacturer. Plus, you’re always free to make modifications, so long as it’s safe and legal.

Keep in mind, the propane tanks you pick up and lug around are most likely DOT tanks that come in 20, 30, and 40-pound variations. The ones built into Class A motorhomes are ASME propane tanks (American Society of Mechanical Engineers).

You’ll sometimes find ASME 30-lb tanks built into Class Bs, while 80 and 100-lb ASME tanks are typically built into Class As. You won’t see 30-lb tanks (of the ASME variety) built into fifth wheels and travel trailers.

How Big is a 30-lb Propane Tank Compared to a 20-lb Tank?

A 30-lb propane tank is about 6” taller and equal in diameter to a 20-lb propane tank. It makes the 30-lb variety easier to identify immediately, simply because of that stretched look that the 20-lb lacks.

In terms of duration, there’s little doubt the 30-lb tanks will last longer than the 20-lb. If it doesn’t, something is suspiciously awry. While you get up to 20 hours of usage out of the 20-lb, the 30-lb should give you at least 22 hours of continuous usage, probably more.

Speaking of size, the size of your wallet may not like the $20 extra that it costs to fill up a 30-lb over a 20-lb. It may not be so bad, depending on where you are, but it can cost between $2 and $6 more per gallon.

Are 20 and 30-lb Propane Tanks Interchangeable On RVs?

20 and 30-lb propane tanks are certainly interchangeable on the front hitch of an RV. The diameter on both is the same, and the bottom base has the same diameter. The only difference is that the 30-lb tank is 6” taller than a 20-lb tank. However, there are some things worth considering before you make that kind of upgrade.

If you have them installed on the front hitch, you’ll add roughly 50 lbs to the weight, assuming you make the switch from two 20s to two 30s. The second thing you need to consider is the difficulty of refilling your 30-lb tanks.

You can get a 20-lb propane tank exchanged for full ones at many different places. With the 30-lb tanks, there are some exchange places out there, but it’s easier to get them refilled at a place that fills them up directly.

You should also consider the different weights in terms of offloading and loading them. The 25-lb tare weight isn’t that big of a deal, but 55-lbs of awkward propane weight is different.

Where Can I Refill a 30-lb RV Propane Tank?

You can refill a 30-lb RV propane tank at a local Tractor Supply, RV parks that offer propane services, some gas stations, hardware stores, U-Hauls, RV dealers, Costco, and local gas companies. With that being said, don’t take it for granted that any of the above will have a 30-lb propane filling service available at all times.

It’s always a good idea to call ahead and make sure. Most hardware and home improvement stores, some feed and seeds, and most Tractor Supply stores will do it. But that doesn’t mean they all will. Gas stations are even more iffy.

If you’re in Tennessee, Florida, or Mississippi, Grill Gas Express will send people out to refill your 30-lb propane tanks on the spot. It’s a huge convenience, and Grill Gas Express is focused on RVers when offering this service. Here’s to hoping it continues to grow and expand to other states.

Can I Exchange an Empty 30-lb Propane Tank for a Full One?

Yes, you can! You can find propane exchanges at some Walmarts, Home Depots, Lowes and even some grocery stores.

Home Depot and Lowes are best known for exchanging 30-lb tanks. However, like refills, you should always call ahead and make sure before you head in that direction. You might be surprised at how many local businesses will do it, assuming they themselves purchase propane.

Final Thoughts on 30-lb RV Propane Tanks

That’s a lot of information just for 30-lb propane tanks, but, as we mentioned before, these tanks are the beating hearts in our RVs. If you’re new to RVing, whether it’s full-time or part-time, it’s best to know the ins and outs of your propane.

When it comes to 30-lb propane tanks, they’re the most commonly used when you account for all RV types, from travel trailers and fifth wheels to motorhomes of all types. While 20-lb propane tanks are common as well, it’s best to get used to the advantages of a 30-lb tank and know its capabilities inside and out.

About the Author:

Thomas Godwin is a full-time freelance writer with a BFA in Creative Writing, a U.S. Marine, and an avid outdoorsman.

When he’s not writing, he’s raising chickens and Appleyard ducks. Thomas also constructs teardrop campers (attempting to anyway) and kayaks the Blackwater River with his wife, two daughters, and his Dobermans.

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