20 lb vs 30 lb vs 40 lb Propane Tank- The Right One for RV

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Introduction

You might not see it often, but campers call the propane tank the ‘nerve center’ of an RV.

Apart from having one, choosing the right size comes as a tough decision to make. Would you go for a lightweight, easy to carry 20 lb tank? Or a heavier but longer lasting 30 lb/40 lb would be wiser?

We’ve taken this into concern and crafted out every single difference among 20 lb vs 30 lb vs 40 lb propane tanks right in this article. Starting from the size and capacity, we’ve talked about the lifespan and cost of them. Finally, we’ve recommended the right tank(s) for each kind of RVs.

Makes sense? Let’s dive in-

20 lb vs 30lb vs 40 lb Propane Tank: Head to Head Comparison

For those of you who’re in a rush, here is the gist of our whole comparison between 20 lb, 30 lb and 40 lb rv propane tanks-

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20 lb vs 30lb vs 40 lb Propane Tank: In-depth Comparison

Shape and Size

All of the 20 pounds, 30 pounds and 40 pounds propane tanks sport a cylindrical shape.

On the top part, you’ll have a collar with a carrying handle. Also, there is an OPD valve that prevents overflow.

On the bottom, there is a round base to stand it upright. But with tanks that can be put horizontally, there is a set of bracket feet across the round part.

However, as it’s about size(dimensions), there are a number of differences between these tanks.

Here is the list-

  • The Height- The height(distance from top to bottom surface) is 17”-19” for 20 lbs tanks, 23”-25” for 30 lbs tanks and 29”-31” for 40 lbs tanks.
  • The Diameter- As long as it’s a cylindrical shape, both width and breadth are referred to ‘diameter’. For all 20, 30 and 40 lbs tanks it’s 12”-14”.

Weight

The lighter your propane tank is, the easier it is to carry on your RV, right? Well, that’s not the end of the story. Bulkier tanks like 30 lbs or even 40 lbs tanks contain perks that you might want to go for.

As long as the weight of a propane tank is concerned, there are of two of them-

  1. Weight while empty(Tare Weight or T.W.)
  2. Weight while filled with propane.

Tare Weight

As you have seen, the empty cylinders of 20, 30 or 40 pounds capacity feature the same diameter. But the height varies a few inches, which we’ve discussed before.

Therefore, the tare weights of these are 5-6 pounds distant from each other. Here is the list-

  1. Tare Weight of 20 lbs propane tank: 16.6 pounds.
  2. Tare Weight of 30 lbs propane tank: 23.5 pounds.
  3. Tare Weight of 40 lbs propane tank: 29 pounds.

You can get this data also from the collar of the tank, where it’s printed as “T.W.: 16.6 lbs” or so.

Full Weight

Once filled up with propane, the weight of the tank raises to 180-200% of its Tare Weight. The density of propane is 493 kg/m3 or 30.8 lbs/ft3. That tells us that, 1 gallon of propane weighs 4.4 pounds.

Considering all these maths, propane weight & full weights of these tanks come to be-

Propane Weight

  • Propane weight of 20 lbs propane tank: 19.8 pounds
  • Propane weight of 30 lbs propane tank: 30.8 pounds
  • Propane weight of 40 lbs propane tank: 41.36 pounds

Full Weight

  • Full weight of 20 lbs propane tank: 36.4 pounds
  • Full weight of 30 lbs propane tank: 54.5 pounds
  • Full weight of 40 lbs propane tank: 70.36 pounds

Capacity and Lifespan

One of the most asked questions regarding propane tanks is- “How long does a 20/30/40 lb propane tank last in an rv?”. That brings to the calculation of capacity and lifespan inside the tanks.

The Capacity of a propane cylinder to contain propane is not fully utilized in any LP cylinder. Usually, 80% of the space is fulfilled and 20% of it is kept empty. For example, a tank that contains 7.5 gallons of propane, can actually contain 9.37 gallons.

This is so because due to the variation of temperature, propane volume can expand to some extent. This empty 20% is used to house the extra volume then. Otherwise, it might lead to an explosion.

About the question of lifespan, it’s not an answer of one word. You need to go know this information before you are able to calculate how long your tank would last for-

  1. The amount(lbs) or propane remaining in your tank.
  2. The BTU/hour demand of your gas appliance/burner.

Before we proceed, these two terms are needed to break down in further details.

Calculating The Inventory of Propane

This is rather simple. All you need to do is weigh your tank, and figure out the Tare Weight(T.W.) of it, which is printed on the tank neck.

Once you got those, subtract the tare weight from the total weight and you’ll get it right away. Make sure that you have this value in pounds(lbs).

Example-

  • Tare weight of a 20 lbs propane tank is 16.6 lbs.
  • Total weight of a 20 lbs propane tank is 26.4 lbs.
  • Propane weight is (26.4-16.6) 9.8 lbs.

Calculating ‘BTU/hour capacity’ of The Appliance

Let’s keep these two things on mind first-

  1. It takes 2 horsepower(H.P.) to generate 1000 watts of energy.
  2. 1 horsepower(H.P.) takes 10,000 BTU/hour.

Keeping them in mind, let’s find the BTU/hour for a 5000W generator that has a 10HP engine and which runs at a 50% load usually.

At 50% load, it would use half of its horsepower. Therefore, 5HP(10 x 50%) would be the available HP.

For each 2 HP, it would generate 1000 watts of energy. Therefore, 5HP would generate 2500 watts.

Each HP consumes 10,000 BTU/hour. So, 5HPx10,000 BTU= 50,000/hour

Once you get those values in hands, the steps are as simple as below-

Step 1: Get the weight(lbs) of propane remaining in the tank.

Step 2: Multiply the propane weight with 4.4 to get the volume(gallon).

Step 3: Multiply the volume with 92,000 BTU(as 1 gallon of propane contains 92,000 BTU capacity).

Step 4: Get the BTU/hour demand of your gas appliances or burner.

Step 5: Divide the BTU capacity of the propane(step 3) by the BTU/hour demand of the appliances.

Step 6: That’s the number of hours that the furnace will run for(theoretically) with the propane.

Let’s do a few examples-

How Long Does A 30 lb Propane Tank Last in An RV with A Generator?

For instance, let’s say the generator is 5000W, 10HP and it’s working under 50% load. If so, then-

  1. Propane weight in the tank is (54.5 lbs – 23.5 lbs) 30.8 lbs.
  2. The volume of the propane is (30.8 / 4.4) 7 gallon.
  3. Total BTU capacity of the propane is (7 * 92,000) 644,000 BTU.
  4. The BTU consumption of the generator is 50,000/hour.
  5. The runtime of the generator is (6,44,000 / 50,000)12.88 hours.

So, a 10HP, 5000W generator working on 50% load can run for 12.88 hours with a full 30lbs propane tank.

Under the same circumstance, here’s a quick chart of what all 3 sizes of tanks would last for how many hours-

Table: Runtime of propane tanks for a typical RV generator

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In case you would like to calculate the BTU/hr consumptions of other RV appliances, here is a quick chart-

  • RV Grills: 8,000-10,000 BTU/hour.
  • RV Refrigerator: 1500-1800 BTU/hour
  • RV Furnace: 20,000-30,000 BTU/hour
  • RV Air Conditioner: 5,000-12,000 BTU/hour

In case you need the exact data of BTU consumption, check out the product body or the user’s manual of your appliance. Once you know this exactly, calculating your propane tank lifetime becomes quite easy through this method.

Recertification

Recertification or requalification is a kind of inspection of propane tanks. After a certain time period, each of the tanks needs this. And this process costs a few bucks for 20 lbs, 30 lbs, 40 lbs and any other sizes of tanks.

Now, which one costs how much?

Before answering the question, let’s clarify the recertification period. For all of 20, 30 and 40 pounds of tanks, the recertification period is 12 years straight. And this expiration date is usually printed on the tank collar.

Let’s get to the cost now.

  • Cost to Recertify 20 lb Propane Tank: $10-25
  • Cost to Recertify 30 lb Propane Tank: $25-35
  • Cost to Recertify 40 lb Propane Tank: $35-45

That being said, this price completely depends on your location. For example, in Central Florida, recertifying a 30 lbs tank costs $15. The same thing costs about $30 in some other states within the US.

However, if you find the cost of recertifying almost close to the price of a new one, we’d always recommend getting a new one. Period.

Price

Although, many of the campers won’t bother the price of a propane tank if it can serve them for quite a while. But for those who’re RVing full time, cost does matter.

That being said, the price range for these tanks vary within a range for each of the sizes. 20 lbs DOT vertical tanks costs from $30 to $60. The OPD sibling of these usually cost about $110-$150.

Moving forward to the 30 lbs tanks, you’d find a price range of $40 to $70. The horizontal 30 lbs ASME tanks come with a price of about $250.

Lastly, it’s the bulkier 40 lbs tanks that cost about $100 to $130. There are some vertical-horizontal models that cost about $200.

There is just the empty cylinder price. You need to fill it up with propane once bought.

For these diverse price ranges, we’ve found out the best tanks to buy for your RV. Here is the recommendations-

Best 20 lbs Propane Tanks for RV

Best 30 lbs Propane Tanks for RV

Best 40 lbs Propane Tanks for RV

If you decide to grab accessories that enhance the safety and convenience of these tanks, here’s a list of them with price-

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Which Propane Tank Would Fit Your RV?

We’re glad that you’ve made it till this point of the article. And you’re not going to regret it. Now, here goes the propane tank size recommendations for different kinds of RVs-

Propane Tank Size for RVs depends on what kind of vehicle you’re in, and your camping needs. We’re trying to take a skeptical approach based on types of vehicle-

Propane Size for Small Class C Motorhome/Truck Camper

Small Class C motorhome or small truck camper owners prefer to go with a few (2 or 4) 20 lbs tanks. Two are for use, and the other two are as a backup.

Same goes for other small RVs like Class B camper vans, mounted truck campers, etc.

As they are light in weight, you can easily carry them along for an exchange or refill. Unlike the heavier tanks, you don’t have to stop the entire RV whenever you’re running out of fuel.

No hard feelings to go with one or two 30 lbs tanks in a small RV. But in those motorhomes, space is the ultimate premium.

Our recommendation: Four 20 lbs propane tanks.

Propane Size for Fifth Wheel Camper/Pop-up Trailers

Pop-up trailers or fifth wheel camper owners prefer to have two 30 lbs propane tanks whenever they go camping. Because they have that space to house them, and fuel consumption is way higher than smaller RVs.

Sometimes, to meet excess usage of energy, you need to put a series of 30 lbs tanks together. Specially trailers with utility quarter, medium-sized class C motorhomes etc would be in this list.

Our Recommendation: Two 30 lbs propane tanks.

Propane Size for Class A Motorhome

There are a number of variations within Class A motorhomes. For Non-pro conversion RVs, we’d go for 2-3 of 40 lbs tanks or 4 30 lbs tanks.

But for class A conventional or professional conversion RV’s you might not be able to meet ends with DOT propane tanks.

Because, such Class A motorhomes come up with quite some space to house a vertical, ASME tank. So, instead of portable DOT tanks, 80-100 lb built-in ASME propane tanks are quite common to such RVs.

Our Recommendation: Two-three 40 lbs propane tanks or one 80-100 ASME tank.

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