If you’ve read my guide to calculating how long your propane tanks will last, then you know estimating the answer involves math (yuck). And your forecasts will never be 100% accurate. If a 40-degree cold front blows in, you could burn through propane twice as fast as anticipated!
If you don’t want to whip out a calculator before every trip … there’s an easier way.
You would think that RV manufacturers would have automatic fuel gauges for your propane tanks. Kind of like you have a fuel gauge for your gasoline, right? Or at least something like an oil dipstick, which you can check occasionally?
Wrong. Most stock RVs don’t come with propane tank level sensors.
You gotta get your own. To whit, I have listed eight methods below. (Foreshadowing: Number 8 is my favorite!)
Table of Contents
RV Propane Things To Know
- Propane tanks are measured by volume, not weight.
- Portable “vertical” propane tanks are certified by DOT.
- Fixed “horizontal” tanks are certified by ASME.
- Generally, steel DOT propane tanks must be recertified every 12 years.
- Common sizes are 20, 30 (33), and 40-lb tanks
- The tank poundage (e.g. 20 lbs) is the nominal weight of the propane the tank can hold when full, although the actual amount might be less to allow for expansion and pressure relief. It’s all part of the RV propane safety system.
- Your RV propane system powers your furnace, water heater, stove, oven, and absorption refrigerator.
0. Go With Your Gut
Many RVers have been camping 40 years and never, ever thought about their propane tanks. If you are a summer-only camper, a single propane tank might last you an entire year!
But it only takes one experience waking up on a November night at 3:20 a.m. with the furnace out, shivering under your covers, cursing your partner (how could he forget to check the tanks?!), to change your way of thinking.
1. Auto-Changeover Regulator
Most RVs nowadays come with A) at least two propane bottles and B) an automatic changeover valve propane regulator. And that little device makes all the difference.
An auto-changeover regulator drains one propane tank dry and then automatically switches to the next. Most have a red/green indicator to show which tank is empty. You simply connect both tanks to the regulator, open the valves on each tank, and let the regulator work its magic!
When the regulator detects an empty primary tank, it will switch to the other cylinder and change the indicator to red. You can remove the empty cylinder without disrupting the flow of propane; the regulator has a built-in check valve.
Here’s an excellent forum description of how an automatic propane change-over regulator works.
You never know how much propane remains in your primary tank – but that’s OK. You simply know one tank is totally empty and needs refilling. So long as you keep an eye on your regulator, you’ll never run out of propane!
- Fairly inexpensive ($55-$95 for auto changeover propane regulator)
- Simple visual indicator
- Doesn’t show actual tank levels
- Requires manual monitoring
- Regulator often hidden underneath cover
- No good for RVs with only one tank
2. The Hot Water Hack
Here’s an oldie but a goodie, straight from Jeff Foxworthy’s You Might Be a Redneck If …
- This method requires a pot (about 4-6 cups) of hot water. Doesn’t have to boil (although boiling is usually alright). Lukewarm water won’t work.
- While running a propane appliance (that part is crucial!), pour a bucket of hot water over your propane tank.
- After the hot water has slightly cooled (usually just a few seconds), run your hand down the side of the propane tank. You should feel a definite temperature change somewhere on the wall. That’s the spot the liquid propane is turning into gas. That’s how full your propane tank is.
This method works because when liquid propane evaporates to a gas, it absorbs a LOT of heat. We engineers would call that the latent energy of an endothermic phase change – but yeah, no on else cares.
Sometimes, you can feel the temperature difference with a dry hand, but because water absorbs heat 25 times faster than air, it works much better!
By the way, a “full” propane tank isn’t really full. DOT propane tanks are generally filled about 80 percent by volume to allow for expansion. You aren’t being cheated; you’re being kept safe.
- Basically free
- Good party trick
- Time-consuming and annoying
- Wastes water (important when boondocking)
- Can be difficult to reach propane tanks underneath covers
- Can’t be used for propane bottles stored in compartments, like in 5th wheels
3. Magnetic Temperature Strip
These $8 strips work essentially the same way as the hot water trick: They detect the temperature differences on the tank sidewall.
Again, these strips have the same limitations as the hot water method: Must be manually monitored, only works while propane is running.
One isn’t long enough to cover your whole tank; you’ll need to purchase several if you want full-scale readings. Otherwise, stick it to the bottom of the tank and monitor it for when the LP gets low.
Watch for color shifts on the temperature-sensing crystals.
- Black, Dark Blue: COLD – Liquid Propane
- Green: MEDIUM – Transition Zone
- Red, Orange: WARM – No Propane
These are also known to blow off tanks exposed to the wind. Fair warning.
- Less work than hot water method
- All cons of the hot water method
- Only measures small section of tank
- Can’t read in the dark (or direct sunlight)
- Can blow or fall off
4. Pressure Gauge
Many RVers have purchased a $20 propane tank gauge at some point in their RVing career. Most, to be honest, move on.
These gauges are not, shall we say, renowned for their accuracy. These gauges simply measure the outlet pressure of the tank, and there are several big problems with this:
- The outlet pressure (somewhat) varies depending on the rate of propane flow. So these gauges only work well when propane is being used!
- The outlet pressure varies depending on the ambient temperature. So the pressure changes if it’s a hot day or a cold day!
- The outlet pressure of a tank, all other things being equal, is mostly constant regardless of its fill level. The pressure only begins to really plummet when the tank is darn near close to empty.
So these gauges, despite their appearance, aren’t really incremental gauges. They’re empty/not-empty indicators. Once the needle falls to yellow, head for the propane store!
If you see one with a simple “Full-Low-Empty” gauge, you know it’s junk.
If you want a simple pressure gauge, get the Camco version. It has a dial indicator with levels divided by temperature (aka Cool Day, Cold Day, Hot Day).
- Effortless to install
- Works with any DOT propane tank
- Easy to read
- Not very accurate
- One gauge required for each tank
- Can’t read in the dark
5. Weigh The Tank
Weighing the tank is one of the most accurate methods.
You can weigh a tank many different ways, though.
- You can give it the ol’ bicep test: Disconnect the tank from its bracket, lift the thing, shake it around, and mutter, “Hmmm … doesn’t feel quite empty.”
- Or you loosen the tank from its bracket and lift it with a fish scale or grill gauge crane scale. Do a little math on your smartphone calculator (subtract tare weight from measured weight), and you’ll know exactly how much propane you have left.
- Or, best of all, you can use a dedicated propane scale.
Several companies, like Flame King, make halo propane scales for 20-lb, 30-lb, and 40-lb DOT portable propane tanks. You need one scale per tank. Each scale – usually shaped like a halo – is mounted underneath your tank.
These scales are wireless and battery-powered. Most connect to your smartphone through a Bluetooth connection. You’ll need to download the company’s app to monitor your tank LP levels. I don’t know of any RV tank halo scales that have a digital readout directly on the halo (it would be almost impossible to read, wouldn’t it)?
I like the idea of a weight scale, but they can present their own problems. They just aren’t compatible with many RVs.
They need a flat surface to sit on.
They might not be compatible with tank bottom spacers or stabilizers.
- Remote monitoring
- Incremental gauge readings
- Need a smartphone
- Must tare different tanks (steel vs aluminum, for example)
- Not compatible with many RV designs
6. Translucent Tank
This is some next-level stuff. You can buy a composite fiberglass propane tank with semi-translucent walls. Viking and Ragasco are major manufacturers.
These tanks are … controversial, to say, the least.
Some say they’re safer because they don’t explode at high temperatures; they just melt. Some prefer them because they’re about 40% lighter than a steel tank.
Others hate ‘em. They break easily. They don’t fit the same equipment as regular propane or aluminum tanks. They cost a $100, minimum. They can’t be swapped out. They have shorter interval inspection periods.
- Resistant to corrosion
- Easy visual inspection
- Dimensions may not match steel cylinders
- Must be recertified more often
7. Infrared Thermometer/Camera
If you’re a techno-overachiever, then I have the solution for you: Buy a thermal imaging camera. Turn on your stove. Point the camera at your propane. See how much propane is left.
(It’s also $500, minimum).
The poor man’s version is a simple infrared thermometer, like you use for taking a child’s temperature. Point the thermometer at the tank to find the thermal transition zone.
I can’t, in good faith, recommend this method. I have a fragile ego, and if anyone caught me “taking the temperature” of my propane tank, I would be so embarrassed, I would shrivel up on the spot.
- Keeps your hands clean
- No remote monitoring
- Definition of overkill
7. Ultrasonic RV Propane Tank Sensors
This solution, my dear friend, is the best way to measure your propane tank levels. What you need is a battery-powered, magnet-mounted, ultrasonic propane tank sensor.
Popular manufacturers include Mopeka, Lippert, and AP Products.
These round sensors fit in the palm of your hand.
- Stick ‘em to the bottom of your propane tanks (use some double-sided tape if you dont’ trust the magnets).
- Download the manufacturer’s app.
- Connect the sensors to your smartphone or tablet via Bluetooth.
- Then you can monitor the actual amount of remaining propane anytime you want! You’ll normally need to be within about 50 feet of the sensor for it to transmit.
RV tank propane sensor is the only solution that ticks off everything we need: accurate results, incremental readings, and remote monitoring.
The AP Products Tank Monitoring system comes with its own wireless monitor, which you can install almost anywhere inside your RV! Here’s an excellent write-up I found online guiding you how to install the AP Products system.
Other systems, like the Lippert Smart Propane Tank Sensor, require a smartphone. If you’re annoyed by that fact … well, then you probably aren’t reading this paragraph. You stopped after the Hot Water Hack (which has worked well for 20 years, so why fix what ain’t broken?)
P.S. You may need a tank halo spacer or spacer feet depending on how your propane tank is mounted and which system you purchase.
- For the AP Products system, if you have a 40, 30 or 20-lb DOT propane tank, spacers are usually required. These spacers prevent the tank from crushing the wee sensor underneath!
- With the Lippert sensor, no halo spacer is required. The ultra-thin sensor won’t get squished.
Pro Tip: You can increase the interval reading time of the sensors to extend sensor battery life!
- Accurate results!
- Incremental readings
- Remote monitoring
- Instant results
- Keeps your hands clean
- Not free
- (Might) require smartphone