UPDATED 2021
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 4 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 like to winter camp and chase powder. Having a little warm water for the dishes is REAL nice.
If we lived down South and weren’t interested in chasing snow, 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 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
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/petrol fired and has 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
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.
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.
Our affordable 12 volt van hot water system
We opted for a 12 volt system that heats while driving or on shore power. This avoided the complexity and cost of a coolant heated version.
You can run it off batteries sparingly but it does draw quite a bit of power. The version we built uses about 35 amps while the element is going. The element of course turns off once up to temperature.
We used a residential Reliance 6 gallon hot water heater. They now have a 2.5 gallon version that might be a good option but I’m not sure how it would do for an actual shower.
These are of course designed to run off 120v which we wanted to avoid so we swapped the heating element to a 12v 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***
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 is designed for.
Going with the 200 or 300 watt element would likely 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
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.
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.
Hey! Super cool setup, but I was wondering how exaxtly it’s linked so that it only works when you’re driving? I’m building a van and looking for hot water options, I already have an induction cooktop so I don’t want to ask any more from my battery. Do you have a drawing or anything that explains this better?
Thanks! I actually just have it wired through a relay and switch that I can turn on and off as needed. It doesn’t automatically turn on while driving although you could wire it that way. If you shoot me an email I’d be happy to shoot a few photos or video showing some more details. [email protected]
Really like your 12V hot water setup. You mention “The element of course turns off once up to temperature.”. Are you using the original thermostat on the hot water tank (so 12V goes to the thermostat vs. directly to the 12V element) or are you using some other thermostatic control that you can set to your preferred temp? Also are you using something like a Shurflo water pump to pressurize your hot water tank? Thanks!
The wiring is no different than if you were hooking the hot water heater up to 120. The only difference is the element has been swapped out to the 12v version. So you still connect your 12v power to the regular hot water heater wires which go first to the thermostat then to the element based on whatever water temp setting you set. And yes we are using a Shurflo water pump. We have several years with our hot water tank and have been full time in the van for a bit and it is working fantastic. We can even keep it on all day charging from our solar on a sunny day.
So if I understand correctly, the thermostat is also running off of 12v DC? It doesn’t require 120 AC?
That’s correct. The only power going to it is the 12V which is wired just like you would if you were installing it for 120v use.
August, I like the reassurance that you have installed an electric water heater with a 12 volt heating element. Regarding the thermostat on the water heater, I read that you did not replace the original one that came with the tank with one that could handle higher amperage. I may use a 600 watt element, and I would not use the original thermostat because that would be 50 amps, and I understand that the thermostats that come with water heaters are made for less amperage. If I used a 300 watt element, I would feel safer with using the original thermostat because it would be lower amperage. It would be 25 amps.
Also, how was the water heater wired with a switch on the wall in the kitchen? I’m assuming that the kitchen switch was connected to a relay, and wasn’t the thick copper wire that goes between the battery and the water heater element?
Jay, That sounds like a good plan with the thermostat. Like you mentioned I only pull about 25 amps so I am not worried about taxing the thermostat. But anything more would be concerning. The wall switch runs a 100 amp relay that is located right at the water heater.
What’s your reasoning for a 600 watt element? I find ours heats pretty quick.
I built a very similar system following your lead using the 2.5gal Rheem heater and 300W Missouri Wind and Solar element you suggested, but encountered this problem with amperage. The 300W element at 12V was drawing twice the amperage as the manufacturer DC element. The thermostat ECO switch failed and required replacement. I installed a 150W element and now it’s working great. Thanks for the great idea on a cheap and simple hot water system! To get a 150W element I just wired half of this double element: https://www.amazon.com/gp/product/B017VT68XA/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1
That’s good to know that was too much amperage for that smaller unit. The one I had was a 2000 watt heating element which pulled around 18 amps at 120v and now pulls 25amps at 12v. Glad you were able to find a solution.
I wanted to install this 4Gal Rheem “Minitank” (or any similar 4Gal tank – Bosch makes ones) and switch to a 12v DC heating element (which also means running the water temp thermostat off 12v) – is that the model you used? Could you explain again (sorry!) the problem you encountered and your solution?
Thank you
Hi Todd,
I only have experience with the model that I used but these slightly smaller models should work as well. The model I used was the 6gal Rheem. The first thing I would look into is what size heating element they use and can you find one that fits that’s a 12v version. My only concern with those smaller units is that they may use a really compact or short heating element that will not be available in a 12v version.
I was wondering if August (or others) could specify the answer RE: location of waterpump like a Shurflo or SeaFlo.
Does the setup go:
Water Tank -> Pump -> “Y” Splitter leading to Hot or Cold -> Cold to faucet mix valve, Hot to water heater -> Water heater output to faucet mixing valve?
(in other words, the 1 and only pump is “upstream” of the water heater and pushes water through?
Hi Steve,
Yes that sounds correct.
The pump can go right after the water tank. I installed a drain valve between water tank and pump to allow for winterizing. After the water pump I T’d off to several different circuits and put a ball valve before each one. The reason being was that for short trips where I knew I wouldn’t use shower or hot water heater I didn’t want water in those circuits to make winterizing easier.
The hot water heater just needs a single pressurized cold line going to it and then you can tee off the hot water line as much as you need based on your appliances.
Awesome little write up. Were in New Zealand, so we have 240v AC for on grid.. Am I correct in assuming the voltage going into the thermostat doesn’t matter, as its just a open / closed switch depending on temperature? We’d just need to get the 12v element and hook the 240v thermostat on the rheem cylinder up to the 12v battery and were good to go? We would obviously have a main / cut off switch for when not in use.
Yes that sounds right. The thermostat must just be a mechanical on/off based on the set temperature. For the main cut off switch I used a resettable breaker like this one. https://amsolar.com/rv-inverter-accessories/brkr-dc-brkr
Thanks for this post. This is a revelation to me that you can change an appliance that easily. Did you change the wire to connect the heater to a 12V plug? What size battery are you using? I have a 100Ah Lithium battery. It has a maximum charging current of 80A, so I assume this would work for a short period. I also assume that being a 200-400W heater it would take much more time to heat up. Do you have a sense of how long?
The 12v wiring going to the hot water heater will have to be sized correctly for how long the wire run is as well as the amperage/watts you end up going with. By “12V plug” if you mean a cigarette lighter plug this draws far too much current for that. This needs to be hard wired and fused. It will draw about 30 amps when running. I have the 400watt and it gets plenty warm for a shower in about an hour. I have 400Ah of Lithium as well as solar. With just 100Ah I would just heat the water heater while driving(if you have alternator charging) since it stays hot for quite a while.
Hi guys! love the set up, trying to replicate it for my van conversion but wondering what size cable you used to hook up the alternator? Thanks!
Hi, I would need to know a bit more about your electrical setup. I wouldn’t recommend going direct to alternator. Shoot me an email at [email protected] and we chat some more. Thanks
Hi August – do you have any concerns regarding bacteria/etc? Many bacteria thrive in temperatures between 20-45C, e.g. https://www.haspod.com/blog/health/legionella-water-temperature.
I’ve been doing the calculations for for my potential setup and seems unavoidable to have to use UV and/or chemical treatment to keep things safe – going to 65C is too energy intensive. How have you dealt with this issue?
I keep my thermostat pretty much maxed so it’s no different than a residential hot water heater. I’m not sure what the range is on my thermostat but I think the typical residential recommended water temp is around 120f or 48c. So yes if you are going well below that I would be concerned as well. I find that once these are heated up it takes relatively little energy to keep them hot.
Very nice write and water heating solution. Do you have any sort of controller or 12dc regulator between the alternator and tank or is it just a relay? I am also getting a Ford Transit with dual 250AMP alternators. Is your water heater connected at all to the house batteries or the van AGM batteries?
Sorry for the late reply…The only thing I have between the starter battery and the house battery is a battery isolator from BlueSea. That disconnects them while the engine is not running so you don’t kill your starting battery. I do not have any DC to DC regulator. Depending on your battery setup that might be a good idea. I can see up to 100amps coming from the alternator to my 300aH lithium which is okay for lithium. That however would be too much for a single 100ah battery.
I know the article is from nearly a year ago, just found it after coming through the Texas ice Storm(s) of 2021. Will be modifying my stuff to prevent future issues. I am also an RV and Electronics tech by trade.
I have some reservations about using DC current through an AC thermostat. If it were me, I would have used a relay / solenoid controlled by a snapdisk in place of WH thermostat.
I have used electric water heaters in mobile setups, and commissioned several for customers. When shore power was available, there was option of running water heater at 240vac, 120vac (reduced heating) using a 240vac tstat. When boondocking / traveling down the road, AC power was created using an inexpensive dedicated inverter. Modified Wine Wave.
Inverter kept close to batteries, minimizes DC cabling. All repair / consumable parts were off shelf available. Element was a 240vac 1000watt. 4Amp @ 240vac current draw, resistance was around 60 ohms. At 120vac, only about 2 amps of current, 250 watts. 250watts through inverter with 90% eff was about 22Amps, depending on actual battery voltage.
Thanks for the feedback and it looks like you’ve built some nice setups. I didn’t have any concern about running DC through the AC thermostat because the thermostat is just a simple contact relay that opens or closes based on a mechanical temperature sensor.
This is a great idea and I’m gonna have to do something similar on my build. Curious about your wiring after the conversion. Did you remove the AC plug and rewire with your own cables. Do you have a wiring diagram to share? What size fuse did you use?
Thank you,
Ron
I’m really sorry for the late reply. Mine didn’t actually come with a plug as it was designed to be hard wired. But I just simply hooked it up like it was being connected to 120v except it was just 12v. I used a 12v 40 amp breaker so that I could kill power to it when it’s not in use or empty.
Hi. This is a great post – thanks. I’m about to start my water system, and I’m doing something similar. I have a heat exchanger system by Bobil Vans, which takes heat from the diesel heater, but also have a 300W element. I was wondering how you power your element using shore power (240V here in the UK): do you simply keep the connection to the battery, but keep the battery topped up with a charger? Or do you have some other way of getting 12V from your mains hookup? Also (if I’m allowed another question!) someone else asked about whether your hot water tank is pressurized. I am intending to do the same, with a Shurflo pump, but was concerned that cold water will mix with hot, as soon as I start drawing any hot water out of the top of the tank. Am I missing something? Thanks again – great system.
Hi Jack sorry for the late reply, I have a 12 volt 40 amp lithium battery charger that is connected to shore power. So that powers everything when on shore. Even my 120v is powered by the inverter that is running off batteries that are being charged by the 40 amp charger.
Yes the hot water tank is pressurized so cool water will be added as you pull hot from it. I don’t have any issues with that probably because I don’t use it a lot. My wife and I can both take a quick efficient shower no problem. If i’m not worried about battery level I usually throw on the element when taking a shower but it honestly isn’t necessary. For a smaller tank like a 2.5 gallon that might not be the case. Our next build will have a smaller tank.
Thanks for the writeup! This seems more efficient than the bosch 120 heater and sounds like it holds heat longer. I would imagine the 2.5 galloon version would heat up much sooner. Do you notice that this radiates a lot of heat into the van? I would want this primarily for the kitchen sink but am wondering if this would have the unintended affect of having a “heater” on in the summer. It sounds well insulated so maybe not.
I don’t notice any heat coming from it, the shell feels just a touch warmer than the room temp. I usually turn the thermostat down during the summer anyways.