Tankless (On-Demand) Water Heaters

Tankless (On-Demand) Water Heaters

Let me say up front, I’m not an expert on RV water heaters. 99% of my experience is based on using our Truma AquaGo Comfort Plus system while living and travelling full time in our RV for the past 3 years. We mostly stay in parks with full hookups but do stay in parks without sewer several times a year. We rarely dry camp. How we camp definitely affects our attitudes toward tankless. The Truma AquaGo systems are arguably some of the best you can buy and the Comfort Plus model is the best of the best, but they are also some of the most expensive. For this post I’m talking mostly about hot water for fifth wheels and travel trailers. Large class A rigs may have other options (Oasis and Aqua Hot for instance) including those that run on Diesel or other fuels that are beyond the scope here.

Recently there have been a lot of questions on RVillage and Facebook about tankless water systems and whether someone should upgrade. Everyone has their opinion and there is both good information and bad that people share. To write this post, I’ve tried to capture a lot of the feedback other RVers have shared along with some information from the manufacturers and of course my own preferences and opinions. Hopefully, you will find this information helpful but I warn you – I’m biased based on how we use our RV and the heater we have. We love our Truma system!

One thing I’ve noticed in quick replies to questions asked online, at least I’m guilty of it but others are as well, is that we all assume everyone uses their RV the same way we do. Most questions are answered in a paragraph or two and the answers do not do justice to the questions asked. Worse, they could be misleading to someone who uses their RV differently than the person answering the question. For anyone looking into tankless, there is no right or wrong answer. Everything depends on how you use your RV, your preferences, and how much money you want to spend. Do your research and see what others who actually use them have to say about the models you are considering. Be careful about reviews on sites that sell products though as the reviews may or may not be fake. Also be careful on sites that compare the top 5, 10 or whatever number of products. They often don’t do any reviews but just repeat the manufacturer’s information. Often these sites steer you to particular units as “the best” but they may just be the ones that earn the “reviewer” the most money.

When looking at tankless water heaters both minimum and maximum flow rate is important. Manufacturers don’t always make that information easy to find but they should tell you if you contact them. Minimum matters because you need enough flow to keep the burner on. For example, an Oxygenics shower head uses about 1.8 gallons per minute (GPM). If you are using a hot/cold water mix or are turning the water flow down to reduce water usage, you could get below the flow needed to keep the burner lit. For maximum flow you probably need enough for your shower and probably another faucet. You might need more if you have an onboard clothes washer. Truma says their unit supplies about 2.4 GPM and we haven’t had any flow/temperature issues running our shower, clothes washer and a faucet at the same time. Lower minimum and higher maximum flows are better.

Tank type water heaters are typically 6-12 gallons in size. Based on the flow of the Oxygenics shower head, that only allows for the shower to be on 3-1/2 to 7 minutes before your hot water is exhausted. If someone or something else is also using hot water at the same time your shower time would be less. If you plan to dry camp then propane capability is a must for either type of heater. The best option for a tank type is one capable of running on both propane and electricity. Also look for Direct Spark Ignition (DSI) rather than ones that use a pilot light.

Finally, check for any notes about operating at high altitudes if that applies to your travels. Many units explicitly say they may have issues at higher elevations. The time to find that out is not when you’re camping in the mountains!

Many people are rightly concerned about the safety of propane. Be sure you have a working propane detector permanently mounted in your rig. I also suggest buying a portable hand held detector you can use to “sniff” around your tanks, regulators, and lines. Don’t just assume you will be able to smell or hear any leak. We recently found a bad pigtail going to one of our tanks by noticing unusual usage and then sniffing around the hoses with our portable detector. It’s also recommended to have your propane system regularly checked by a professional. If you do these things, you are unlikely to have an unexpected problem or fire due to propane.

Tankless vs Tank water heater guidelines

You might want a tankless water heater if…

  • You are a full-timer
  • Multiple people camp together in your trailer and everyone wants to take a shower in a short time frame
  • Your rig includes a dishwasher or clothes washer
  • You like taking long, hot showers
  • You typically stay in places with full hookups

You might want a tank type water heater if…

  • You want to minimize install cost. Cheaper tankless systems may approach the same price as a good tank type but you may be disappointed in cheaper units
  • You don’t use a lot of hot water – if you currently have a tank type and don’t run out of water you may not need to upgrade to tankless
  • You go camping infrequently
  • You are happy taking “navy” showers
  • You typically stay in places without full hookups (see Truma below for how they help in this situation)
  • You’re thinking of buying tankless to save money

Pros/Cons of Tankless Water Heaters


  • Unlimited hot water – dishwasher, clothes washer, long hot showers
  • No recovery time between uses
  • Can be turned on and left alone – provides an experience close to what you would have in a house with minimal manual effort
  • Some systems allow for an adjustable output temperature but that may force more manual control effort
  • These systems tend to be lighter
  • Even though their burners are larger, they use less propane than a tank type in propane mode because the burner is on much less – unless you use a lot of hot water continuously!


  • High purchase cost
  • You cannot heat the water in a tankless system using electricity (Oasis and Aqua Hot claim to be able to provide “low demand” hot water from 110v electricity but those are not really just a tankless water heater – they are more)
  • There may be a learning curve to learn how to effectively use it
  • Propane water heaters may not work as well as electric in low temperatures or high elevations
  • There could be a delay for hot water when turning on the water although this is typically 2-4 seconds. Truma has largely solved this (see below)
  • If you use a lot of hot water you could increase propane usage over a tank type because you can essentially get hot water forever until you run out of propane
  • They are rare enough in the field that getting a certified tech to repair them can be difficult
  • Even though you may use less propane, don’t assume you can save money in the long run. In our house we installed tankless and cut our gas usage in half but even with a self-install to save money, it was going to take about 5 years to break even on the investment

Pros/Cons of Tank Type Water Heaters


  • Low purchase cost
  • Most support operation with both propane and electricity


  • Uses more energy, particularly if left on, since it has to keep the tank hot
  • Hot water limited to tank size (can take about 30 minutes to heat back up when cold)
  • May need to be manually turned on/off to save energy particularly if using propane
  • May need more manual interaction if using both electric and propane simultaneously for quicker recovery
  • Can be damaged if powered up with no water in the tank
  • If propane only, propane water heaters may not work as well as electric in low temperatures or high elevations

Thoughts about specific brands

There are several popular brands of tankless water heaters on the market for RVs. I know most about Truma since that is what we own but I will also mention a bit about some of the other brands that frequently come up.


As mentioned before, Truma produces tankless water heaters that are arguably the best you can buy. The downsides of Truma is that they are among the most expensive and they are intended to be installed and maintained by a Truma certified technician. As such, it appears that parts would be difficult to obtain including a complete replacement unit although we did meet someone whose unit went bad and Truma did send a unit for him to replace himself. It may also be more difficult to find someone certified to service a Truma unit. We have not had an issue with ours in over 3 years as full-timers so we haven’t been able to see this for ourselves but lack of parts availability and difficulty finding a certified repair center could be a huge issue.

Now let’s look at why Truma are so good (and so expensive). First off, the units use a 60,000 BTU burner so they have sufficient heating power to use in cold weather and to produce enough hot water for multiple outlets to be open at the same time. The unit comes pre-set to deliver 120°F water at up to 2.4 GPM and the temperature is not user adjustable. The flow rate is plenty for a shower and something else at the same time. Even though the Truma does not have an adjustable temperature, we use it just like you would in a house – mixing hot and cold water at the faucet to get the temperature you want. The minimum flow rate to turn on the burner of 0.4 GPM ensures hot water even when flow is reduced to barely more than a trickle.

Except for the Truma Basic version which must be turned off and drained in freezing weather, Truma Comfort and Comfort Plus models when turned on and operating normally will automatically protect themselves in freezing temperatures by running the burner to keep the unit above freezing. For times when you don’t want to use propane to keep it from freezing or when travelling with propane turned off and temperatures are below freezing, they offer a 12 volt electric anti-freeze kit that can be self-installed. 

Some people have commented that propane can be Less efficient in certain conditions such as low temperatures and/or high elevations. We have been in temperatures down to -5°F, below freezing temperatures for days and elevations up to 9000’ and have not experienced any issues with these problems. I can’t say it didn’t use more propane or that it didn’t burn as efficiently at higher elevations but we always had plenty of hot water.

Unlike other water heaters, Truma’s products contain a temperature stabilizer. This is essentially a small .35 gallon water tank that gets pre-heated as the unit runs to minimize outlet temperature fluctuations due to pressure or flow changes that may cause the burner to temporarily shut off. We have found outlet temperatures to stay rock solid even in a variety of operating conditions. This may also help reduce the restart delays when taking “navy” showers if you still want to do that.

While the burner will start within 2-4 seconds after the minimum water flow is achieved by far the biggest disadvantage to tankless is that during that time water is being wasted while you allow the water to start heating. 4 seconds isn’t very long but when you’re boondocking that is a substantial amount of water being wasted. Imagine taking a “navy” shower, you turn on the water for a few seconds, rinse, then turn it off. Then soap up and repeat the process. During that time, you’ll either have hardly any hot water, or you’ll be wasting water. Neither of which you want to do when dry camping. The temperature stabilizer will help by delivering hot water without the huge drop in temperature when washing off the soap unlike other units.

An even better solution to that problem is the Truma Comfort Plus (CP) model. This model allows creation of a continuous loop between all faucets and returning to the Truma CP. In “Comfort” mode, the hot water is circulated through the loop via a small pump in the water heater even when all the faucets are closed. The net result is near instant hot water to the faucets in the loop. When we are in a situation where we need to conserve water or reduce gray water we use this mode and we can take “navy” showers using less water than would be used even with a tank type heater because we don’t have to wait for hot water to flush the cold water out of the pipes before initially rinsing off. WARNING! While handy, comfort mode uses a lot more propane than the Eco mode that does not continuously pump water through the loop. We use it while taking a shower and then put it back to Eco mode afterwards.

The downside of the CP model is that Truma says it can only be OEM installed since it requires a hot water loop to be plumbed when the rig is built. Aftermarket, it would be difficult if not impossible to add the loop. So this model is only for new units being built for the most part.

One comment that frequently comes up on blogs is that tankless systems use more propane because their burners are larger. For example, tankless typically have 40,000 to 60,000 BTU burners while tank type heaters have 10,000 to 12,000 BTU burners. Looking only at the BTUs is misleading because you also have to look at the duty cycle of the burner. A tankless system might run the burner a dozen times a day for short periods of time whereas a tank type, if left on, will cycle the burner on and off throughout the day to keep the water in the tank hot. Of course, you could turn the tank type system on and off manually but with tankless it’s all automatic. How annoying is it to go to take a shower only to realize you never turned on the heater? Now you’re waiting up to 30 minutes for the water to get hot!


Over the years, I have consistently heard of problems with Girard maintaining a constant temperature. Some problems may occur when limiting water flow to conserve water as it needs more than twice the flow as Truma to keep the heater on (0.9 GPM according to their Troubleshooting Guide). Others say you must be sure no one else opens a faucet when you are taking a shower. Other problems occur if the park’s water pressure varies. There are also many reports of it never reaching the set temperature. I could not find a flow rate for their GSWH-2 model online but it appears to be less than 2 GPM. The burner on this unit is 42,000 BTUs which is 1/3 less than Truma and could be a contributing factor to a lot of the problems. These problems may contribute to more water use which could be a major issue if dry camping. To work around these issues, many people set a comfortable temperature for their shower and then use only hot water (no cold mixing) to keep flow up. They also make sure nothing or no one else uses hot water during a shower.

Some newer reviews are more positive than older ones which may indicate that Girard is making improvements. Still, most reviewers talk about it being finicky, talking a learning curve to figure out most efficient use, and subject to variations due to water flow (too much or too little), water pressure, and low outside temperatures. Support from Girard also seems to be a bit hit or miss as well with people saying it took numerous times sending emails or leaving voice messages before they got a reply. Then Girard wanted them to do a bunch of tests before telling them there wasn’t anything wrong with the heater. Others reported good customer service however and many of those were more recent so maybe that is improving as well.

In comparing to Truma, Girard is much less expensive by about 1/2 (<$600 retail) and for DIY types it is available for self-install although they do not recommend you do that. Parts are also readily available. The manual also states that it can provide anti-freeze protection as long as it is operating and has propane but it does not offer any protection while travelling so it must be drained if freezing temperatures are expected. Unlike Truma, it does not have a temperature stabilization tank so there may be a larger dip in temperatures if the burner is stopped during a shower and then restarted. Girard also does not offer a model with plumbing loop capability to provide instant hot water like Truma does.


I have seen other people’s reviews of Suburban and Dometic tankless and reviews have been somewhat positive, particularly for the Suburban model. Reports say it will handle multiple faucets at once with little or no change in temperature. The temperature can be adjusted via an optional remote control. Some set the temperature they want and only use hot water (no cold-water blending). It has multiple burner settings and up to a 60,000 BTU burner. For Dometic, there seemed to be a larger learning curve and it might be necessary to only run one thing at a time. Interestingly the Dometic review I found might have been on a discontinued model. I even see some Dometic “Tankless” models advertised online but in looking at the Dometic site, I don’t see one. The model I saw online wasn’t tankless even though it was claimed to be – again do your research,

Some VERY inexpensive (<$500) units are made by CampLux, Marey, Eccotemp, Excel and others. Some have flow rates too low for even a single shower while others seem to have very high flow rates. Most of these don’t seem to be designed specifically for RV use and most are not in the typical footprint of an RV water heater. I’ve seen great reviews for most of these online but I personally would stay away. I’ve learned when something sounds to good to be true, it usually is.


For us, even though tankless systems are at best break even in cost over a LONG period of time, we prefer our Truma over tank type costing 1/4 as much due to the ability to turn it on and forget it no matter what our situation is whether in full hookups or dry camping. We take showers as long as we want and never have to worry about running out of hot water even if we’re washing clothes and doing dishes all at the same time. It’s much more like the experience of being in a sticks and bricks. Just because we’re in a campground doesn’t mean we have to give up too many comforts – especially since our RV is now our house. That’s just us, your goals and wishes may be different,

I hope that this information is helpful if your are buying a new rig or replacing the water heater in one you already own. There is no right or wrong decision, decide what’s important to you and go with it after doing your research to make sure it will be what you want and expect.

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