We don’t have a propane tank in our van, so we heat our water using the electrical system. It’s a choice that works for us because we have a large battery and solar system. Here’s a description of our system and the other options you might consider.
We plumbed our van with a cold and hot water tank. The hot water tank is an Isotemp slim square unit. It has a tempering thermostat so the water in the tank can be heated much hotter than would be comfortable to use, then it’s mixed with cold water as it comes out so that it is at the right temperature. That way, the 4 gallon tank can provide many more gallons of hot water.
The water stays hot in the tank for a long time – we’ve used it two days later and been surprised at how warm it was.
The tank has a 750W 120V immersion heater element inside it. It also has a separate heat exchanger “coil” that allows hot water from another source like your engine coolant to run through the tank and heat the water in the tank. More on that later.
The 4 gallon tank takes about an hour to heat up to the point where its thermostat turns off. Our unit actually draws 860W from the 12 Volt system (there are inefficiencies with the inverter converting to 120V), so it’s consuming around 71 Amp-hours from our battery each time it heats up from cold.
That’s about 1/10 of our battery capacity, so we’re OK heating a tank of water every day if we want to. Our solar panels are capable of replenishing that energy most of the time. Obviously, we also try and plan ahead and heat up the tank while we’re plugged in to shore power at home before we leave on a trip.
Isotemp do make other tank sizes, and their cylindrical tanks are cheaper. We just didn’t have the space to put anything other than the rectangular one. It fits next to the 3-person bench seat.
If we don’t want to heat a whole tank, we have two other options. We have a travel kettle. Boiling water in that takes 860W for 5 minutes. That’s obviously much less water, but it’s enough to wash dishes or clean up. We also sometimes heat a little water in the pan we’ve used for cooking. Again, that’s really handy for doing the dishes.
We also have a portable solar shower. Actually, it’s just a big black bag that hangs up in the sun. We use the 10 liter MSR Dromedary bag with a shower attachment. It’s sturdier than most of the plastic solar showers you can buy. In the summer this heats water up enough to feel good when you’re cleaning off after a bike ride.
One thing we will do when we have the time is figure out how to use the hot water tank as a diversion load for our solar panels. When the battery is fully charged, the solar controller switches off. All of that sunlight is “going to waste” at that point. Using our Victron equipment, it’s possible to set up a system that switches on the water heater when the battery reaches a certain state of charge. That would continue to use all the available solar energy and heat our water “for free”!
Other options we considered
On-demand hot water
If you have a smaller battery, it might not be able to sustain a 70 Amp draw for an hour. That would limit an electric hot water tank to only being used on shore power. You might be able to get away with using an on-demand electric hot water heater instead.
We chose to go all-electric rather than installing a propane tank. Obviously, vans with propane systems installed can make use of propane boilers either to heat a water tank or for on-demand water. There are a lot of advantages to this approach. The only real downside (other than having to install and plumb a propane tank) is that most permanently installed propane heaters require a large-ish hole in the side of the van to vent.
If you just want hot water for a shower, take a look at the Zodi system. It uses the 1lb green propane tanks to heat water that is pumped out of the storage case or a bucket.
We don’t have one, but we’ve used one. It really helps to dump the shower head into the supply bucket while you are soaping up. That heats the intake water up and saves water that otherwise would go to waste.
Engine coolant system heating
We mentioned that our hot water tank can be plumbed to run a hose from the engine coolant system through a coil inside the heater. That’s a great way to get hot water if you’re driving every day. If you are camping in the same spot for several days though, you won’t have that source of heat to warm your water. It’s a good secondary heat source, but it’s not the right primary heat source for many people.
Diesel hydronic heater
We have a diesel-fired hot air heater (the Espar Airtronic D2) to warm the van up. You can also buy similar heaters that heat water rather than air. This water can then be stored in a tank or can be circulated through radiators in the van to warm the interior.
We chose not to use this system because it takes longer to get the van interior up to temperature than the D2 does, but it is still a viable option. The hydronic diesel heater can be used in combination with the engine coolant system too, so that either source heats the vehicle interior and the hot water.
Saving the best ’till last (?!), there’s no reason why you shouldn’t just heat water on a small camp stove to use for all your washing needs. In combination with a cheap 12 volt shower head, you can even use this water for showers.