campervan hot water heater

MY $300 DIY 12-VOLT CAMPERVAN HOT WATER HEATER

*UPDATED 2021* – NEW 12 VOLT WATER HEATER RELEASED THAT’S DEFINITELY WORTH A LOOK. PLUS, FIND OUT WHAT WE WILL BE USING IN OUR NEW EARTCRUISER CORE BUILD.

Deciding on whether to have a hot water system in your van can be a tough decision.  It can add significant cost and complexity.

I settled on a bit more of a DIY version that costs less and for the past 6 years has worked great.  Let’s have a look at the most popular hot water systems and why mine is a great option if you don’t have deep pockets.

DOES YOUR CAMPER VAN NEED HOT WATER?

I know you want it but do you really need it.  Obviously a very personal choice here.  

We opted to go with hot water because we are full-time and having a hot shower was a must. If we lived down South and didn’t chase snow for skiing, hot water might have not been such a priority.  But for us we absolutely love it!

CAMPERVAN HOT WATER HEATER OPTIONS

Let’s have a quick look and get familiar with the different ways you can live the good life with hot water in your van.

COOLANT HEAT EXCHANGE SYSTEMS

In my opinion, this is the top dog in a campervan hot water heater.  These work by having a water tank that is heated by coolant that circulates through it.

While driving the coolant from the engine heats it or you can heat it via a diesel/petrol fired coolant heater.

This system even allows you to preheat your engine block which is a great feature for the cold.

Isotherm campervan hot water heater


IsoTherm
 is just one option but a very reputable one that has a long following in the sailing and yachting circle.  Just the tank will run you about $750.

To heat via coolant lines you’ll need to tie into the engines coolant system which is no small task.  For us the cost was too great and a bit complex for the DIY’er.

DIESEL OR PETROL FIRED HOT WATER SYSTEMS

webasto dualtop hot water heater

The Webasto Dual Top is another great option and avoids the complexity of tying into your engine’s coolant system.  The Dual Top also provides forced air heating in addition to hot water.

These are diesel fired and have an internal 11 liter hot water tank.  These can even be mounted outside of the living area underneath your van.  They have built in freezing protection features as well.  Not cheap though at about $3,500.

PROPANE ON DEMAND HOT WATER SYSTEMS

on demand propane hot water


These are becoming a popular option for those that are using propane.  These on-demand hot water systems can be hooked up to a propane tank and work great for outdoor showers.

You’ll see people with these hanging on their back doors.  They are not designed to be used inside because they require ventilation.  They are however very affordable at around $200.

rv hot water heater

Here you have the traditional RV propane hot water heater.  These require a large hole cut in the side of your van and in my opinion are a pretty dated way of going about hot water.  There are far better options in my opinion.

Rixen Hydronic with S-3 Diesel or Gas Furnace Kit

The Rixen heating system which is found in numerous professional van and RV builds offers some unique features. The system works by heating a reservoir of radiator fluid which is then pumped to heat exchangers for hot water or heaters. In addition, the system can be built to to integrate with the engine heating system.

Rixen 12 volt heating system

That lets you get free heat while driving and allows you to preheat the engine in cold weather. While plugged in to shore power the system can also heat by way of the integrated 120v heating element.

Rixen Enterprises has built a custom control board which integrates with the gas furnace and the Comfort Hot hydronic reservoir. In addition to letting you “set and forget” your temperature it provides options for integrating gas fired, shore power, and electric for your heating. The thermostat also comes with two zones so you can customize settings for different zones of your camper. Great for keeping an eye on temperatures in your camper garage area.

The system is very modular letting you expand and add heating capacity as needed. While it is rather pricey at $4,500 it’s the clear winner for me in terms of function, being compact, and versatility with engine heat and expansion. This is the system we will be installing in our new Earthcruiser CORE chassis so stay tuned for an unboxing of the system and install.

OUR DIY BUDGET 12 VOLT VAN HOT WATER SYSTEM 

This is the system that we currently have in our camper van which was priced right and has worked great for us. But if I were to do it again I would have a good look at the 12v water heater mentioned below or go all in with the Rixen system mentioned above.

This DIY 12 volt hot water heater pulls about 35 amps while it’s on (depending on heating element size) and stays plenty warm throughout the night even when the unit is turned off. We primarily had it on while driving as it stayed plenty warm for hours once turned off.

diy hot water heater for van

We used a residential Reliance 6 gallon hot water heater.  They now have a 2.5 gallon version that might be a good option for folks.

These are of course designed to run off 120v which we wanted to avoid so we swapped the heating element to a 12v element.

diy 12 volt heating element


The 12 volt heating element that we ended up going with was the 400 watt from Missouri Wind and Solar.  READ THE UPDATE BELOW WITH OUR NEW RECOMMENDATION

The Missouri Wind element comes in 3 different wattages.

  • 200 watts drawing about 16 amps
  • 400 watts at 35 amps
  • 600 watts drawing about 50 amps(NOT recommended)

***UPDATE 2021***

12 volt heating element for campervan

While we have never had any problems using the 400 watt heating element that draws around 35 amps, some have reported that the their thermostat stopped working after a while.  This is likely due to the 35 amps of current which is more than what the thermostat on the 120v model is designed for.

Going with the 200 or 300 watt element should solve this issue.


HEATING ELEMENT SWAP

Swapping the element is easy and no different than any other hot water heater.  Here’s a video showing how if you’re not familiar with it.

12 VOLT WIRING DIAGRAM

DIY campervan water heater wiring diagram

PARTS LIST

HOW HAS OUR SYSTEM WORKED?

We’ve been running this setup for over 6 years and it has worked flawlessly.  Absolutely no issues.

Once the water heats up it stays relatively hot for a good 16 hours.  At least warm enough to do some dishes.  When we take showers we try to do that after it’s been on for a while.

We typically don’t stay parked for days at a time without driving to trailheads and such so we never have a problem warming it up.  And when on shore power you of course are golden.

We use it a lot in winter and is easy to drain to prevent freezing.  We just ran a drain pipe through the floor.

IMPORTANT THINGS TO CONSIDER WITH THIS DIY HOT WATER SYSTEM

In our Ford Transit we have a heavy duty alternator so I’m confident we have enough spare amps to run the hot water heater as well as charge our battery bank while driving.

It’s important to know what your alternator is putting out because this could be a big drain and cause premature alternator failure.

It’s also important to never turn on the heating element without water in the tank. It will ruin the element.

We have an illuminated switch for the heater above the sink but I was afraid we might accidentally turn it on without realizing it.  So I installed a second inline switch that kills power to the whole system that I turn off whenever I drain the tank.

This assures that even if someone turns the switch above the sink on there will be no power going to the hot water heater.

NEW – 12 Volt Water Heater for Vans and Campers by EX-UP

This is looking like a really good option but I have yet to hear from anyone that’s used it. I do however trust Andreas who runs the company that is importing them. It’s the first unit like this that’s truly designed for a 12v system and doesn’t cost a fortune.

12 volt water heater

Here are some details from the Expedition Upfitter.

Our 12V-6 Liter water boiler is designed to fit in motor homes, vehicles, boats (sail and power) with a standard 12 volt hook up and adjustable thermostatic control from approx. 30 ° C to 75 °C .  It’s equipped with overheating protection, anti-backflow (water), and electricity leakage protection as well as a safety valve set to avoid overpressure.

The tank holds 6 liters or 1.6 gallons of hot water and when mixed with cold water you increase the amount of warm water 2 to 3 times. There is an ultra-thick foam layer to keep the tank well-insulated inside its steel cover. The tank is enamel coated and uses advanced anti-corrosion technology making this a great water boiler for your adventures.

The 12V Water Heater is hand and pressure pump capable. Purchase a pump that works at less than 4 Bar or 68PSI.

Adjustable Thermostat: 30°-75°C (86°-165°F)
Size: 45x 27x 27cm (18×10.625×10.625”)
Weight: 2.8kg (6.3lbs)- Empty
Power Consumption: 12 Volt -200 W (17A)
Heating Time: 30-45 mins depending on cold water temperature (55°C / 131°F)
Over pressure safety: 4 Bar
Water Capacity: 6L (1.6G)

FINAL THOUGHTS

Like i mentioned earlier, we’ve been running this system for 6 years now without a single hiccup.  It works great on shore power, battery(sparingly), and of course while driving.  

Because the tank is round it does make it a little awkward and not very space efficient.  I really like the IsoTemps mentioned above because they offer a square version. 

But for a hot water system that works great and can be done for well under $300 I’m very happy with it.

I hope you found this article useful and please don’t hesitate to ask questions.

Don’t forget to follow our adventures on Instagram @outsidenomad and be sure to share this on your favorite social media so you can reference it again later.

14 thoughts on “MY $300 DIY 12-VOLT CAMPERVAN HOT WATER HEATER”

  1. I’m planning to install a 12v heating element in a plastic water tank. I want to keep the element from bouncing and loosening or touching the bottom of the tank. What would you put between the element and the tank to keep the element stable?

    1. I’m not sure I understand. How big of a tank? When you say “between the element and the tank” where exactly do you mean? My initial gut feeling on this one is that it’s a really bad idea. Are you planning for a blow off system if it becomes over pressured?

  2. Can this same method be used for the Bosch 3000t and The Camplux ME25 models? It looks like they also have an anode but I prefer those because they are cheaper and BETTER insulated. Thanks for the great post and info.

    1. Kris,
      I really can’t say for sure but here is what I would check. First make sure they have replaceable heating elements that are the industry standard threading. Then make sure that the 12-volt heating elements will fit and are not too long. I would also recommend going with a lower wattage heating element since I don’t know how many watts the existing thermostat of the water heater can handle.

  3. This was a really helpful post, and has me inspired to try the same with a Stebel 4gal water heater I just purchased. Where I’m hung-up, however, is how the 12v element is controlled by the 120v thermostat…I can’t imagine the 12v element is just connected directly to the battery without the use of a thermostat…is it? Are you able to swap the 12v element in and connect 12 volts directly to the tank and have it work properly? Any clarification here would be greatly appreciated!

    1. I used the 120v thermostat that came with the tank. I just simply swapped the heating element out for a 12v and then wired it up just like you would for 120v. The thermostat is really just a switch that opens and closes based on the water temp. Instead of it switching 120v power it will just switch the 12v power.

      1. So If I understand, it is as simple as swapping the element, cutting the 120v plug and attache it to the 12v circuit. No electronic to modify or anything… Pretty plug and play if that is the case. Thank you

  4. I am upfitting a van and like the idea of a small electric water heater. I will have lots of solar (420W), a big lithium battery (430Ah) and a DC-DC converter just in case. What concerns me is the heating time for a 10L heater with a 300W element. At home we use a standard Bosch 2.5 Gal 1,440W heater and it takes about 20 minutes to get to full temp (140F). If the heating element is only 300W, wouldn’t it take almost 2 hours to reach the same temp? I am considering the Duoetto 10L which is very similar to the one you mentioned but larger capacity. It also has a 300W element.

    1. It will take a while to heat. I don’t know how to calculate the time but there probably is a formula for that. 2 hours sounds a little long to me but I can’t say for sure. I typically would turn it on while driving since I didn’t have a ton of battery. So for us that time didn’t really matter.

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