Off Grid On-Demand Water Heaters


Having hot water while living off grid has never been easier.  Traditional hot water heaters are energy hogs.  Boiling water on the woodstove takes forever.  Luckily On-Demand Water Heaters are here to save the day!

The best off grid on demand water heater uses propane and a battery and connects easily into your existing plumbing.  Rinnai water heaters have been found to be one of the industryʻs best water heaters, reliably providing instant hot water over many years with little maintenance.

Before we run out and pick up a Rinnai On Demand Water Heater for our off grid homestead, itʻs important to note that not everyone will need the same water heater.  Depending on your needs, you may need a small water heater or a big one.  Or maybe on only one faucet?

Iʻve been off grid for a long time.  Iʻve gone through a couple of water heaters.  Here are my 3 favorites that have served me well throughout the different evolutions of my homestead.

My 3 Favorite Off Grid On-Demand Water Heaters

The Beginners On Demand Water Heater: Camplux 5LOpens in a new tab.

CampluxOpens in a new tab. designs their equipment for outdoor lifestyles, but this small water heater can also be used indoors. It’s a good option for individuals or small living accommodations, such as one-room cabins or RVs.

When I first started out, it was just me in my one room off grid home.  I got it while building because I was able to easily connect a hose to it and take a shower in 5 minutes.  My bathroom wasnʻt even built yet, but I still wanted to clean up after a long days work.

Great thing was, once the shower was built, I could install it for long term use.  Itʻs capacity was limited, best for 1-2 people, but it was a great cheap option for those early years.  They do have larger sizes, but I like other brands if Iʻm thinking about going bigger.

One cool feature is that while this heater runs on propane, the ignition is via battery power (2-D cell batteries), making this a simple, compact off-grid solution for hot water.

More features:

  • Safety sensor allows indoor installation
  • Safety Features: Oxygen Depletion Shut-off, Overheat protection, Flame Failure Device and more
  • Runs on Propane Gas
  • Ignites with 2 D cell batteries
  • Works with very low water pressure (3.0 PSI)
  • Is compatible with a 12-volt water pump
  • Only 10 lbs

Maximum BTUs: 28,000 per hour
Gallons Per Min: 1.32, other models have higher GPM

Best Budget On Demand Water Heater: EZ Tankless DeluxeOpens in a new tab.

This company offers a range of tankless water heaters and because they focus just on tankless, on-demand water heaters, they also provide great maintenance and customer service after purchase.

I purchased this model a few years back as my home began to expand.  It got the job done.  Hot water in less than a minute for as long as you needed it.

However, you will need to stagger baths/hot water usage. For example: while someone is showering with hot water, avoid washing the dishes until they are done.

I did have a love/hate relationship with it though.  It has a digital display and ignition, requiring 48 watts for every hour of run time and a plug outlet for it to work.  I normally shy away from things like that. But you donʻt have to worry about the pilot light catching something on fire, which happened to a water heater of mine once.

More Features:

  • Runs on Natural Gas & Propane
  • Self regulating, adjusted amount of heat to suit your needs, depending on if you are using the shower or a sink tap
  • Auto shut-off when water tap is not running
  • Safety measures without pilot light: uses a computer chip instead
  • Works with water pressure as low as 35 PSI
  • Indoor use, installation required
  • Unique feature: vent kit does not need a cover or condensation drain

Maximum BTUs: 82,000 per hour
Gallons Per Min: 4.4, other GPM models available

Best Off Grid On Demand Water Heater: Rinnai

RinnaiOpens in a new tab. is the best in the business and for good reason.  These on demand water heaters last for a long time, which is why Rinnai backs them with a 10 year warranty.

I have a small family now and 2 ladies in the house that need their hot water so we upgraded to Rinnai 5.3 GPM ModelOpens in a new tab..  It still needed to be plugged in but could be installed outside, eliminating the need for indoor exhaust pipes.

Best thing is you can take a shower and do the dishes at the same time without having anyone yell at you to turn off the water.  It was a great addition to the family.

This unit cost more than the others, but I expect it to be with us for a long time.

More Features:

  • Safety features include temperature lock technology
  • Runs on Natural Gas
  • Able to use multiple taps at once
  • Run up to 3 large hot-water using appliances at the same time
  • Can be installed indoor or outdoor, suggested to be done by a professional

Maximum BTUs: 150,000 per hour
Gallons Per Min: 5.3, other GPM models available

Related: Off Grid Appliances: The Complete GuideOpens in a new tab.

5 Things Consider When Purchasing An On Demand Water Heater For Your Off Grid Home

  1. What Size Tankless Water Heater Do I Need For A Family Of 4? How Many GPM’s Should I Get?

    GPMs means “Gallons Per Minute” and refers to how quickly an on-demand heater can heat a given amount of gallons. 

Getting hot water quickly is not the only thing to consider here. You should calculate the maximum amount of water you need for your home, not just an average daily estimate. 

You also need to factor in showering and using the kitchen sink simultaneously. Don’t skimp around here, because you don’t want to have to micromanage your hot water usage. You want to be able to use your water heater without worry.

For a family of 4, aim for 4 GPM or higher. If you’re able to stagger showers and tap usage at the same time, then 4 GPM might suffice. 

On the other hand, if you think you’ll need hot water for the washing machine to do laundry, or other appliances, it is probably better to err on the comfortable side, so shoot for 6 GPM.

  1. What Does The BTU Rating Mean For On Demand Water Heaters?

    BTU is a calculation of the amount of heat needed to take a pound of water by a single degree. Basically, a higher amount of BTUs means a more powerful water heater.

As you can see with my favorite heaters, the Rinnai Tankless heater suggested for a bigger home has 150,000 BTUs, while the smallest guy (the Camplux 5L) has only 28,000.

Bigger heaters do not necessarily mean more hot water, because on-demand heaters supply constant hot water.

Instead, the BTU rating shows the power of the water heater, and if you have more water usage, you need a more powerful water heater, otherwise, you’ll overwork your heater and potentially damage it.

Another thing to keep in mind here is baths versus showers. If you or members of your household like taking hot baths, you should invest in a bigger heater.

  1. Do They Work When There Is No Power?

    Electric vs Non-electric

As you can see, some types of on-demand water heaters ignite with electricity. This can be an obstacle for off-grid homes, so pay close attention when finalizing your choice.

Propane heaters are more likely to be entirely off-grid solutions, especially if they work with a traditional pilot light.

Some newer models, like the EZ Tankless heater mentioned above, use a computer to control the temperature of the tankless system. This does require electricity, so you will need to have a power source or generator in order for it to function.

You can still be off-grid, you just need to plan for electricity via solar power or a generator for your water heater to work.

  1. How Long Do On Demand Water Heaters Take To Heat The Water?

    15 seconds, folks.

Some on-demand water heaters are called tankless systems or instant hot water solutions. I specifically avoid using the term ‘instant’ here because it is misleading. On-demand heaters are not an automatic (or ‘instant’) process.

Just as the name suggests, these water heaters heat ‘on-demand’ instead of keeping a reserve of hot water in a tank. In the long-term, heating water as-necessary results in a more energy-efficient, and lower cost system.

However, the lag time to get hot water with an on-demand system isn’t very long. An average of a 15-second wait is all that is needed to get the hot water running from your taps or showerhead. 


If you’re used to a traditional hot water tank, this can seem like a long wait. But after a few weeks of use, it is easy to adjust to the quick wait and soon you won’t think about those seconds at all!

  1. On Demand Water Heaters Perform Poorly With Low Pressure Systems

    A lot of on-demand water heaters will advertise their ability to function based on water pressure. This is really important, because lower water pressure means slower water, and that results in even more slowly heated water. 

Water heaters are not pumps, so too little water pressure could be an issue. Make sure you have sufficient water pressure for which type of on-demand heater you are interested in.

Some tankless water heaters advertise the estimated elevation for optimal function. While elevation might not matter to us here in Hawai’i, that’s not the only factor that determines water pressure. Know your home’s water pressure output before making a purchase.


While there are fewer options for low water pressure in on-demand water heaters, there are still some good choices, too. My favorite Camplux heaters work with the lowest water pressure on the market – the Camplux 5L needs only 3.0 PSI of water pressure.

  1. You Need Propane or Natural Gas Hook-Up

I like the idea of not having to be reliant on outside sources of energy to my off grid homestead, but sometimes it just makes sense. 

I have to go 3 miles down the road to fill up a 5 gallon propane tank that lasts me 1.5 months.

Sure, heating water with wood would be awesome, but who has the time?  Sometimes you have to take shortcuts where they make the most sense and this is one of them.

Maybe one day Iʻll spend the days needed to cut down trees, buck them up, split them, stack them to dry, then bring it into a woodstove wrapped with a copper waterline that can heat my water.  

Until it becomes necessary, I think Iʻll keep going down the road to fill up my 5 gallon tank.

Alternative Methods To Get On Demand Hot Water Off Grid

On-demand water heaters are one option for your off grid home, but there are other ways of getting hot water, too. 

Solar Hot Water Panels

Solar hot water panels and a solar hot water tank (usually mounted on a roof or other location) are required for this set-up. One drawback is that lack of sun can affect the quantity of hot water on a given day. Rainy seasons or very cloudy periods might result in warm-but-not-hot water.

Typically an on demand water heater is used as backup in these situations.

Related: Solar Hot Water Panels vs. The RainOpens in a new tab.

Biogas Hot Water Heaters

If you’ve got plenty of animals or a large amount of bio-waste on your homestead, then you might want to look at biogas alternatives. Using biogas energy to heat water is an ideal off-grid solution!

There are some massive biogas water heaters out there, but also (thankfully) some progressive smaller units that work great for showers, including outdoor showers. 

These small units work for a 1-2 person household, and don’t offer kitchen sink or other hot-water solutions beyond showers. One well-respected company making these heaters is a Chinese brand called Puxin.

Woodstove Method

If you have a woodstove, you can wrap the flu with a copper water pipe and heat water while warming your house.  This is a great win-win if you use a woodstove already to heat your home.

Pair it with a backup water heater for storage and you can enjoy hot water for hours after the fire is out.

The drawback with this method is that during the heat of summer, you may not want to use a woodstove to heat your water, because youʻll also be heating the house.

Once again, a back up on demand water heater is typically used for summer months in these situations.

Stovetop Method

This is a pretty obvious solution, but I love the simplicity of it.

  1. Get one or two big pots.
  2. Fill them with water.
  3. Heat them on the stove.

Works to wash a sinkful of dishes, prepare a bucket shower or a child’s bath.

It’s not the most fun long-term solution, but it can be a great backup if you pair it with another option, like if you regularly use a solar water heater and it’s a cloudy day. And, it is an easy way to remain off-grid without a big investment.

Compost-Heated Hot Water

This method runs pipes through compost heaps, taking advantage of the heat energy naturally created by compost piles. Pipes or hoses coil through a pile of compost and can connect to your home’s shower or outdoor or kitchen sink for an alternative source of hot water.

It’s not endless, though, and how long this option will last depends on the size of your compost pile as well as the length of pipes being heated by the compost. 

Typically, the set-up can last a few months. As your compost pile changes and shrinks, so will the availability and temperature of hot water. If you prefer this method, you will need to build a new compost pile (and coil your pipes or hoses through it) a couple of times each year.

I think this system is a great way of stacking functions.  It does not depend on propane or natural gas and does not require a big investment of money. 

But, the time and set-up of compost-heated water might be demanding.  It is also quite annoying dealing with all those water lines when youʻre trying to use your compost pile.

Really, there are so many options for off-grid hot water. From propane on-demand heaters to compost-heated water and everything in between, it is really easy to go off-grid and still enjoy hot showers on your homestead.

Sean Jennings

Sean has been living simply Off-Grid in Hawai'i for over 18 years. He lives debt free on Hawai'i Island with his family and over 40 chickens. When he's not tinkering around the homestead, he's off exploring the shorelines for fish & surf.

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