Learn About Off Grid Water Heater Systems

Written by Regina Cal
Published on December 21, 2019

Last Updated on May 16, 2022

Share this

Off-grid living is all about building systems. And one of those systems that we don't want to live without is hot water. 

We have become accustomed to having hot water at the turn of a faucet, but that nicety hasn't been around for long in our human history. Sure, you could live without a hot water system and boil water in a kettle, like our great-grandmothers. It's not a necessity to survive, after all. 

But who wants to live without hot water? 

I will not live without a hot water heater system, but I have learned to live with less hot water. 

As you will find out in your off-grid journey, anything requiring energy is expensive, time-consuming, and can break down. Energy is the most complicated piece of the off-grid puzzle, with heating and cooling usually being the biggest challenges. 

This article discusses the best, most energy-efficient methods for off-grid hot water heater systems. Some of them are expensive, and some of them you have to build yourself. Some could be a temporary measure while you work on installing an upgraded water heating system. 

If you are new to off-grid living and just getting started building your off-grid water system, check out my article How To Build an Off-Grid Water System.
best guide to off grid hot water heater systems

Off Grid Water Heater Energy Sources 

As noted above, heating and cooling systems require the most energy and are the most challenging systems when going off the grid. Living the off-grid lifestyle means trying to be independent of municipal utilities as much as possible. 

Every situation is different, so you have to decide what is right for you, what you can afford, and your resources.

The four primary sources of energy to consider for heating your water are:

  1. Propane

  2. Solar - read my article on solar hot water heaters

  3. Wood

  4. Electricity

Using wood to heat your water is the most primitive and cost-effective energy resource. However, it is very time-consuming, and wood may not be readily available on your property. 

Solar is also a cost-effective strategy for heating water, depending on how you plan to capture the solar. Some places do not have a lot of sun during the day, which could be problematic. 

Propane is typically the energy source used by many off-grid folks for water heating. But propane is not cheap, and the prices keep increasing as everything becomes more expensive. 

Electricity is not a good option for water heating as the appliances take up a TON of energy, which is a pretty big no-no when living off the grid. Although, I have come up with an electric method that may work for you if you have spare energy.

Let's go into each energy system and discover the best methods for heating hot water off the grid.

burning embers

1. Off-Grid Propane Hot Water Heater

Although propane "technically" is not off the grid because you have to rely on another entity to provide you with energy, it is a very effective method for heating your water, and many off-grid folks use it. That is what I use to heat my hot water! 

Propane water heaters are readily available and not all that expensive. Many rural communities have local, private propane distributors that will install a large propane tank on your property and come over to fill it, so you do not have to drag your tanks down to the shop for refilling. 

Propane is getting more expensive as the demand for gas increases, especially over the winter. However, you can offset this cost by learning to live with less hot water.

One easy way of using less hot water is to turn off your water intermittently in the shower. You can get a showerhead with a pause button and pause the water when you are soaping up. This is what I do, and I save a TON of water and propane!

pausing shower head to conserve hot water

Here is a highly rated and affordable pausing shower head - product link

Off-Grid Propane Tankless Water Heater

Tankless water heaters have become very popular due to their energy-saving design and on-demand hot water.

When you use a tankless heater, you have endless hot water. This is because the water heaters are compact compared to traditional tank heaters. 

Since tankless propane heaters are on-demand, you use less energy as the appliance only heats when necessary.

Tankless propane water heaters last almost twice as long as traditional water heaters do, and they usually come with a solid factory warranty for several years. 

Note that you will probably need professional installation unless you are familiar with gas appliance installations. 

How much propane does an indoor propane tankless water heater use?

There are several factors dictating how much propane your tank will use. The water heater heats up to 120 degrees. How many BTUs it takes to get to that temperature is mainly based on your climate. It is all about your groundwater temperature. 

groundwater temperature chart for USA

Let's use the Northern USA region as an example. It takes an average of 650 BTUs to heat one gallon of water through a tankless propane water heater at an average groundwater temperature of 42 degrees.

The average person in USA uses 12 gallons of hot water per day. 

Multiply your BTUs by gallons:

650 BTUs X 12 gallons = 7,800 BTUs per person per day

Next, we figure out how many BTUs are in one pound of propane - it is 21,548 BTUs. Divide your BTUs per gallon of propane by daily personal usage:

21,548 / 7,800 = Around 3 days of usage per person, per pound of propane. 

With these calculations, one pound of propane provides three days of hot water to the average person. 

This figure can vary greatly depending on your region, seasonal water usage variations, how many people you have in your household, how many appliances are using the hot water, and how much hot water each person uses. So take the time and calculate your hot water usage to determine if a propane tankless water heater is right for your off-grid lifestyle.

Indoor VS Outdoor Propane Tankless Water Heater

As you start to shop around for propane tankless water heaters, you will notice that there are indoor models and outdoor models. The main difference is that outdoor models do not have to be vented because they are installed outdoors. However, if you purchase an indoor model, you will need to vent the water heater properly, which means boring holes through walls.

Another factor when choosing between an indoor or outdoor water heater is condensation. Indoor water heaters not only need to be vented, but condensation has to drain out as well, which means another hole in the wall. 

indoor propane tankless water heater installation in a laundry room

Outdoor propane tankless water heaters do not require venting and can be cheaper than their indoor counterparts. 

However, outdoor water heaters require more propane to heat the water in colder climates, especially throughout the winter. It could freeze the unit and cause irreparable damage if it is freezing out. Not good!

Suppose you are building a new home and live in a cold climate, choosing an indoor tankless water heater that you install while building makes sense. If you add a tankless water heater to an existing build and live in a milder climate, then an outdoor heater makes good sense.

Indoor Propane Tankless Water Heater Product Recommendation

The Rinnai V65iP Propane Tankless Hot Water Heater provides a 6.5 GPM flow rate, accommodating a small to medium-sized home.

rinnai tankless hot water heater

Outdoor Propane Tankless Water Heater Product Recommendation

Rinnai also makes a comparable outdoor tankless water heater. The V65eP model also provides a 6.5 GPM flow rate and works great in warmer climates. 

rinnai outdoor tankless hot water heater

Special Note: 

You can get a portable outdoor propane tankless water heater for very small cabins and camping trips. The Camplux Pro water heater is usually under $200 and is a great hot water option for temporary use or in small, single-person installations.

camplux outdoor propane water heater

2. Off Grid Solar Water Heater

Watch my video on solar hot water heater systems! 

In Israel, a whopping 85% of citizens use a "dud shemesh", or sun boilers, which is a simple device that heats a panel full of water in the direct sunlight. Less than 1% of Americans use a solar water heater, despite all the green talk flying around.  (source). 

dud shemesh solar hot water heaters in israel

A bunch of dud shemeshes on top of apartment buildings in Israel

A solar collector circulates hot water through tubing that sits in the sun, and then sends the heated water into your pre-existing water heater, or to a special water heater built specifically for the system. 

These prebuilt solar collectors can be quite expensive and some require professional installation.

Some systems are easy to install and plug right into your hot water system. The nice thing about solar hot water heaters is that there are no moving parts that can break down, so the unit is virtually maintenance free. You can also get a clean energy rebate for your purchase (check with your local jurisdiction for energy rebates).

Learn even more about solar hot water heaters in my new article! 

Solar Water Heating Panels For Sale

Although there are not many models available in the USA, I have found a couple that are worth mentioning. 

The Sunbank makes a 40 gallon hot water heating panel system that has no moving parts, does not use glycol, and is insulated so the heated water stays hot all throughout the night. 

It is an easy installation for a handy person knowledgeable about basic plumbing techniques. The unit is a couple of thousand bucks, but is eligible for a 30% tax rebate, so check with your local jurisdiction for that hefty rebate. 

solar hot water heating panel Sunbank

The Heliatos hybrid hot water solar panel kit plugs directly into your existing hot water heater. Its a hybrid system, so you can still use your original water heater on cloudy days. This solar water heater is less than a thousand bucks and would work well with a small cabin. You can always add more solar hot water heating panels if your hot water needs demand so. 

solar water heating panels hybrid system

Off Grid Project: DIY Solar Hot Water Heater

Don't want to spend thousands on a manufactured solar heating panel system? Build one yourself for pennies!

The method is quite simple: 

  1. Find a used, broken traditional water heater. You can find one for free at landfills, building supply stores, and local appliance shops. They can't even give these things away!
  2.  Strip away all the bits and pieces until you are left with a bare tank.
  3.  Paint that tank completely black. 
  4. Place the tank in a wooden frame, lined with reflectix. Place a pane of glass on top, you can salvage one from an old window, or sliding glass door. 
  5.  Connect a hose into the tank and fill it with water. You can connect an output hose that gets pumped into your pre-existing hot water heater. 
  6.  Let that baby bake in the sun, and you will have piping hot water!
diy solar hot water heater

3. Off Grid Wood Fired Hot Water Heater

There are so many creative DIY methods of building a wood fired hot water heater, but the basics always stay the same. 

Basically, you have a coil that is heated by burning wood. Cold water enters the coil, gets heated by the hot smoke of the burning wood, and is routed into a pre-existing hot water heater, a hot water storage tank, or a range boiler. 

A range boiler is an antiquated, yet highly effective, way of routing cold water into the heating coils of your wood burning stove and routing the hot water back into the tank for use. 

The cold water in the range boiler sits at the bottom of the tank, while the hot water rises to the top of the tank. Convection replaces the need for water pumps. 

Range boilers are not so easy to come by, so you can build one yourself with a discarded hot water heater. You can read this article about how to adapt an old hot water heater tank into a range boiler. 

diagram for a wood burning hot water heater

Basic diagram of how a range boiler works

Here is a real life example of the wood fired hot water heater using a homemade range boiler: 

diy wood burning hot water heater with range boiler

There are many other methods for making a DIY wood fired hot water heater. Let's go over some more simple designs for off grid hot water heater systems. 

diy wood fired water heating hot tub

This is a primitive coil water heating method for heating up water in a hot tub. It uses basic convection like a range boiler does. The cold water sinks to the bottom of the tub, routes through the coils, gets heated up, and circulates the hot water back into the tub. 

diy wood burning hot water heater made from salvage materials

This old guy got really creative and put a couple of metal barrels on top of a kiln to make off grid hot water. Instead of using coils, you can directly heat a tank of hot water for the same effect. 

copper tubing in a rocket stove for hot water

You can use a rocket stove to heat up water by placing the copper tubing in the chimney of the stove. 

As you can see, there are so many great ways to build a diy off grid wood burning hot water heater. The only downside is that you will have to stoke the fire first before you get any hot water. It takes a little bit of time to get the water to temp, so make sure to preemptively plan your hot showers. 

4. Off Grid Electric Hot Water Heater

Let's get down to the brass tacks. Electric water heaters are not off grid friendly. If you are already off grid, then you know how precious electricity is. It takes swaths of solar panels to run heating and cooling systems. Even a basic coffee maker takes 3 kilowatts a day to run!

Let's calculate how much energy traditional electric tank water heaters need:

Traditional Tank Water Heater Solar Power Calculation

According to energyusecalculator.com, a traditional tank water heater uses 4,000 watts per day and runs for about 3 hours per day. 

A 250-watt solar panel will provide 250 watts per hour when the sun is providing full direct sunlight for about 4 hours per day, equaling about 1000 watts per day output. 

We divide our water heater watts per day usage by how many watts the solar panel provides:

4,000 / 1,000 = 4 250-watt solar panels

That is a lot of solar panels just to power the water heater! This does not account for energy loss from converting the power into A/C, nor does it account for cloudy days. As you can see, a traditional hot water tank is just not all that feasible for the off grid lifestyle. 

Off Grid Electric Tankless Hot Water Heater

These types of hot water heaters are absolute power hogs! It wouldn't really make any sense to try and run one of these off an off-grid energy source whatsoever. 

I was looking at the manual for the Tempra Series tankless electric water heaters and the minimum watts required for their smallest water heater is 9,000 watts. Their largest one uses 36,000 watts!

Now, electric tankless water heaters do take less energy to run than their traditional counterparts because they do not have to run all the time to keep water stored in the tank hot. Rather, they have super powerful heating elements that essentially flash heat the water when you turn on the hot water tap.

This, in turn, creates a heavy load on your electrical system, requiring a substantial increase in amps and breakers. Most normal households on the electric grid require an upgrade to run these water heaters, let alone an off grid power setup.

Let us entertain the thought of using one of these bad boys on an off-grid situation. If I had a mid-size electric tankless water heater requiring 20 kilowatts, I would need 16 deep cycle marine batteries (at 12v 105amp) just to provide the power depth for the heating elements.

These just simply will not work for most off grid power situations. 

Point-Of-Use Mini Tank Electric Water Heater

Not all hope is lost if you are really wanting to use electricity to heat up your hot water. I have found these interesting little mini tank water heaters that install at their point-of-use. These could actually be a feasible solution.  

These mini tank water heaters range from holding 2.5 to 7 gallons of hot water and use 1400 watts for heating. These could be used for a small cabin, installing one for the kitchen and one for the bathroom.

Any more than two point-of-use heaters could add up to a heavy electrical load if you are not careful about when you are running the hot water.

I do think with some careful planning and for small off grid installations, these could work really well.

Bosch Electric Mini-Tank Water Heater

This is a 4 gallon point-of-use water heater that comes in under $200. This uses 1440 watts, which is a manageable electric load. 

bosch mini tank water heater


There are several ways to attain hot water while living off grid that are functional, practical, and energy efficient. Modern techniques give you the option to have on-demand hot water without having to harvest timber or boil water. You will have to spend some $ for the convenience, but I think it's worth it! 

If you have any questions or comments, please feel free to leave them below. 

Thank you for visiting Maximum Off Grid! I have poured hundreds of hours into building this website as a database of off grid living techniques. I hope you have found value in this article. 

You may also like

Does a Solar Water Heater Work In the Winter?The answer is technically yes. However, it depends on the

Does a Solar Water Heater Work In the Winter?

Are you thinking about getting a solar hot water system, but are unsure if it's worth it? Do

Solar Water Heater Advantages and Disadvantages

Watch the Video Version of this Article! The concept of the solar hot water heater is not well known

Get the 101 on Solar Hot Water Heaters

Regina is a solo homesteader in the mountains of Southeast Arizona. She specializes in off-grid system design, alternative building materials, and off-grid water system planning.

  • Hello Regina! Very nice blog. I also use an off-grid water heater at my home and it’s an ideal option for hot water. Thank you for letting us know about some other water heating solutions. I will surely try these too. Keep sharing, keep blogging!

  • Hi! I ben thinking about skiping the boilertank. And go with stove+coppercoil to a radiator instead. Will there be any problems this way?

    • Using a radiator is a creative idea, it pretty much works in the same way as a boilertank. I think it would be ok, however I am not a radiator expert.

      Give it a try and let me know how it goes!

  • Thanks for this blog. I’m looking at building a cabin in the Pacific NW that is totally off grid. You’ve given me a lot of information for me to be able to make better decisions with the planning.

    • Aww thanks! I am so glad I could help you out with all this information I have created. Good luck with your off grid journey!

  • Hello Regina! Very helpful blog! I am a student and for my project we need to come up with a sustainable off the grid house. Which of the water heaters do you recommend. Do you have any tips that might help us?

    • Hi there and thank you! I would recommend to go with the woodstove/coil method. This way you can heat your home, make hot water, and you can also cook on a wood burning stove. Three off grid systems in one!

  • Hello Regina:

    Thank you for the information, it’s straight forward and educational….well done 🙂
    I remember seeing the wood burning hot water tank set up as a kid at my grandparents farm in Quebec. I have recently bought a property on a lake in northern Ontario and I’m starting to look at my options for heating/lighting. I would love to somehow design/build a system that takes all these options and works together I.e solar panels with batteries for electricity, propane, solar hot water and wood burning heating for personal hot water AND in-floor heating of garage and house. I know that’s a lot of things I’ve thrown at you but would appreciate your feedback if you have the time.



    • Hi there and thank you for the compliments! Going off grid is a journey, it takes a whole lot of time and system building and things don’t ever seem to work quite right, lol. I suggest starting with your biggest priorities, electricity and heating. Ontario is very chilly! So you will want some redundancies for your heating. Have propane, wood burning, and electricity for heat source. Do you get much sun up there? How about wind? Wind power is actually great. I would look into that too. I have a podcast episode that covers a DIY solar water heater: https://theoffgridoutpost.com/podcast/going-off-grid/podcast-do-it-yourself-solar-hot-water-heater-for-pennies/. Keep me updated on your journey!

  • Your article is fabulous in everyway, thank you. I’m thinking about building an off grid home, So the details you provided in your article are invaluable to me. Thanks again.

  • Great job. Information given concise manor. The facts in a way anyone can understand. Learned several things for this article. Thanks

  • Hi! My brother made a coil to go in his wood stove and his insurance company came around for verification purpose and they condemmed the hook up. Although it was realy well made and that he used it for years before.

    • That’s terrible! It really makes me mad that these tyrannical controlled corporations dictate what we can and cannot do with our own property!!! Makes me sick!

  • Hello Regina, we have a totally off grid cabin in the Kentucky mountains and our water heater is propane. I have a 1000 gal propane tank that’s been at least 3 yrs so far. Our refridge/freezer and stove are propane as well. We have a 4.5 Kw solar system with batteries. Your article gave me a great idea – use my wood burning stove with copper pipe to pex piping under floor heating system. With a 12 volt hot mash brewing pump that would keep the chill out of my floors!! Thank you for a great brain stimulation!!

    • Ah, I am so glad that my article brought you some good inspiration! We also use propane for our water heating needs and it works just fine. It is probably the most convenient water heating method. Let me know how your floor heating system turns out!

  • {"email":"Email address invalid","url":"Website address invalid","required":"Required field missing"}