Off Grid Water Heater: The Ultimate Guide [+5 Useful Methods]

Ultimate guide to an off grid water heater

When building an off grid lifestyle, there are comforts of modern day living that we just do not want to give up. On-demand hot water is one of the fundamentals that we have grown accustomed to; we feel it is a necessity for life as we know it.

Not too long ago in humanity’s history, hot water was a nicety that was only used for cooking and for the occasional bath. If you wanted a hot bath, you would have to boil water and pour it into a washbasin. I could only imagine how many kids were doused in a tub of cold water!

mom washing kids in old vintage tub
This is the way our great-grandparents washed up!

My appreciation for hot water began when I moved into a camper full-time. We were on a 6-gallon hot water heater which allowed for maybe 5 minutes of hot water. I had grown accustomed to 30 minute luxurious steamy showers where I could daydream and shave my legs at my leisure.

Now, I have to plan accordingly and shut off my hot water intermittently just to have enough to get through a shower.

This really got me thinking about how we can manage to have continuous hot water in an off grid scenario.

As you know me by now, I have spent hours of research building this very article to provide you with the best ways you can build an off grid water heater system so you can enjoy modern day living without being connected to a municipal water and heating source.

Let’s get into the good stuff!

The Methodology of an Off Grid Water Heater

The essence of being off grid is to be independent from municipal sources. Being free from monthly utility bills and providing your home with your own energy is the foundation of living the off grid lifestyle.

There are two commodities that you will need for your off grid water heater: energy for heat and water.

You can learn how to build an off grid water system in my comprehensive guide here.

When it comes to energy, there are three main sources you can harness to heat your water:

1. Energy from the sun

2. Gas in the form of propane

3. Burning wood

Using wood to heat your water is by far maximum off grid. Your system requires no moving parts (which means no breaking down) and you can harvest your fuel from your rural surroundings. This is also the most labor-intensive method as you will need to start your fire anytime you want hot water and you will need to collect your wood.

logs on a fire

Another option is to use the power of the sun with a solar power water heater. You can also use solar power to run a traditional or point-of-use water heater but its not ideal in terms of energy usage.

Propane is a happy medium energy source if you are living off grid, yet close enough to a town to purchase propane or have it delivered to you.

Technically, using propane is not quite off grid since you are relying on a municipal source of energy. That being said, since you are not hooked into the system and do not have to pay a monthly bill for energy, I still consider it off grid. Propane tankless water heaters are a popular choice for rural dwellers and off grid homesteaders.

Using a Traditional Tank Water Heater Off Grid

Traditional full-size residential tank storage water heaters are not the best choice for an off grid situation, and I will tell you why.

Traditional tank water heaters either use natural gas or electricity for heating. Natural gas water heaters are off the table since we are not going to rely on being connected to the gas company for energy.

Electric tank water heaters are an off grid option, but we need to factor in how much energy these units will need to run and if your solar panel setup will cover those needs.

Traditional Tank Water Heater Solar Power Calculation

According to energyusecalculator.com, the typical traditional tank water heater uses 4,000 watts per day and runs for about 3 hours per day. I think these numbers are a little high as technologies have made for better efficiency but it’s probably a pretty accurate figure for a family of four.

A 250-watt solar panel will provide 250 watts per hour when the sun is providing full direct sunlight. We can assume that this is about four hours on an average sunny day. Therefore, our 250-watt solar panel will get us about 1,000 watts per day, on a good day.

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

water heater watts per day / solar panel output watts per day = how many solar panels we need

For our example:

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

That sounds like a whole lot of solar panels just to power the water heater! This is not even considering if you need to draw power from your backup battery bank.

Now, you could settle for a small 6-gallon residential water heater which takes less energy requirements but having that small amount of hot water takes some getting used to.

6 gallon off grid water heater

A typical 6-gallon water heater takes 1650 watts. If we run that through our calculation:

1,650 / 1,000 = 1.65 250 watt solar panels (round up to 2 panels)

This seems more reasonable to me. You will still need to consider having another battery or two for solar energy storage.

Using an Electric Tankless Water Heater Off Grid

The long and the short of it is that a whole house electric tankless water heater just isn’t going to work in a traditional off grid installation.

Now I am no electrician but I can see that the electrical demand these water heaters require is not going to be compatible with typical solar power setups.

I was looking at the manual for the Tempra Series water heaters made by Stiebel Eltron 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.

electric tankless water heater insides

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 a solar power setup.

Let us entertain the thought of using one of these bad boys on an off grid solar power setup. 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 trigger the heating elements. I could only imagine how taxing that large of a draw would be on a battery backup system!

At this point, I am out of my professional scope to further analyze if an electric tankless water heater would work with a solar panel setup, but in my humble opinion, it just won’t – not easily, anyway.

Even the point-of-use tankless water heaters use too much electricity for the standard solar power system.

Do not fret! I have found some sensible solutions to your on-demand water heating needs.

Choosing an Off Grid On-Demand Water Heater

An on-demand (or tankless) water heater can be an ideal solution to your off grid water heating needs. Now we have already debunked whole house electric tankless water heaters as an option, which leaves us with two types:

Propane tankless water heater

Point-of-use mini tank water heater

Although tankless models are desirable because they do not use energy to heat a full tank of water warm 24/7, there is a common misconception that a tankless water heater will provide an unlimited amount of hot water. This is simply not the case.

You cannot run multiple hot water sources at the same time when on a tankless system. Since the water is heated as it passes through the heating elements, it can only provide so much.

It also does not provide an unlimited amount of hot water; the amount of hot water supplied varies by which model you choose. The less energy-intensive the model, the less hot water you will get.

Propane Tankless Water Heater

Even though using propane is not necessarily the most off grid friendly energy source, it makes sense in a lot of situations. Virtually every small town has a coop which provides propane, oftentimes you can have it delivered to your home. You can use it for other appliances too.

Propane wouldn’t work so well for very remote locations or if you are trying to achieve a complete autonomous off grid system.

outdoor propane tankless water heater

How much propane does a propane tankless water heater use?

This entirely depends on your usage. The water heater heats the water to 120 degrees; depending on your region depends on how many BTUs it will take to get to that temperature.

Since I am in Montana, I will use the Northern region as an example. It takes an average of 650 BTUs to heat one gallon of water through a tankless propane water heater.

The average person uses 12 gallons of hot water per day – I think this can be shaved way back with conscientious water usage.

So now, you times your BTUs by gallons:

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

Now, we figure in how many BTUs are in one gallon of propane which is 91,502 BTUs.

Divide your BTUs per gallon of propane by daily personal usage:

91,502 / 7,800 = 11 days of usage per person

So one gallon of propane will provide 11 days of hot water to the average person. That is pretty darn good!

Now, this figure can vary greatly depending on what region you live in, 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 really uses.

Indoor VS outdoor propane tankless water heater

As you start to shop around for these water heaters, you will notice that there are indoor models and outdoor models.

The main difference between the two is that outdoor models do not have to be vented since they are outdoors.

If you purchase an indoors 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.

However, if you choose the outdoor version, it will require more propane to heat the water in colder climates and through winter. If it is extremely cold out, it could freeze the unit and cause irreparable damage. Not good!

If you are building a new home and live in a cold climate, it makes sense to choose an indoor tankless water heater which you can build into the structure.

If you are adding a tankless water heater to an existing build and live in a milder climate, than an outdoor heater is the preferred choice.

Special note on Propane Tankless Water Heaters

You will need some form of electricity to the water heater in order to provide the spark for the ignition.

Some models you will have to wire in and other models run on batteries.

Just a note to save you a future headache!

Point-Of-Use Mini Tank Water Heater

These little electric water heaters are installed at the point-of-use, usually under a sink, and delivers hot water on-demand to the fixture. This makes for way less energy use than a whole house electric tankless water heater.

mini tank water heater

Although it has a tank and is not technically “tankless” it is a small tank and takes way less power than a traditional single-source water heater.

These water heaters range from holding 2.5 to 7 gallons of hot water and use 1400 watts. Not a bad cost of energy compared to other water heaters.

The downside is that you will need to install one under each fixture you plan to use hot water. This 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.

The main concern I have when using these for your off grid home is that you will have to install multiple units which will still add up to a lot of kilowatts. You would have to be very conscientious about which hot water heater is running to avoid overloading your system!

Solar Hot Water Heater

Solar hot water heaters are a completely separate unit from a solar power system.

The system has a heating element that is called a solar collector. In direct active systems, the water passes through the solar collectors and then sends it to the water storage tank.

In indirect active systems, the solar collectors heat up a fluid that warms the water in the tank indirectly. Indirect systems are for installations in cold climates.

solar hot water heater collector

A solar hot water heater can be an excellent choice for an off grid water system, so long as you have a steady supply of sunlight.

These systems require a special (expensive) solar hot water heater which uses a 220 volt heat exchange module within them to keep the water hot.

220 volts adds up to 2,200 watts meaning you will still need solar power to keep that storage tank operational. Not an ideal situation for an off grid home.

Also, if you have several cloudy days in a row and deplete your water storage tank, you will be plum out of hot water. Prepare to boil water in a pot!

Solar powered tankless water heater

So far, I have only found one model of solar hot water tankless heater made by Solcrafte. Technically, it’s not tankless as the hot water is actually stored in the solar collector, but since you do not have to store water in a tank in the home, I will let that slide.

solar tankless water heater

Solcrafte does not list any prices for these solar tankless water heaters, which means they are probably very expensive! Over time, I am sure that tankless solar water heaters will become more prolific and cost less.

Overall, a solar hot water heater could very well work for an off grid installation so long as you live in a sunny climate and have an energy source to run the solar storage water tank.

Wood Burning Water Heater

If you are wanting an autonomous water heating system that does not rely on technology, moving parts, and municipal fuel, then a wood burning water heater is the only way to go.

This is an excellent choice for off grid cabins that are very remote and has a lot of timber available for fuel.

Be prepared to do some wood cutting if you go with this type of water heating system!

From what I have found, there are no premade wood burning water heaters for sale. Alas, they are very simple to make with a little bit of engineering and elbow grease. That’s how we roll when we are off grid – we make shit!

DIY Wood Burning Hot Water Heater

The concept is very simple to build your own wood burning water heater.

You will need:

hot water heater coil for wood stove

Hot water heating coil

wood stove

Wood burning stove

range boiler tank

Range boiler tank

copper tubing

Copper tubing

Step one: affix the water heating coil to the firebox of the wood stove.

connecting water heater coil to back of wood stove firebox

Step two: attach the range boiler heater to the hot water coils.

hooking up range boiler tank to wood stove water heater

Plumb in cold water to the range boiler tank. The cold water sinks to the bottom and outputs to the water heater coil. The hot water inputs into the tank and rises to the top. The thermosiphon effect is good for up to ten feet. If you need the hot water to travel farther, you can use a hot water recirculating pump.

You could also wrap a hot water heating coil around the pipe of a wood stove for the same results.

wrapping water heater coil around wood stove pipe

You can also make a rocket stove water heater by simply placing a coil into the stove.

water heater coil in rocket stove

I hope you have enjoyed my informative article on off grid water heaters! If you use any of these for a solution, drop me a comment and let me know how things go!

Regina, owner of Maximum off Grid

Hi, I am Regina, the creator of Maximum Off Grid.

My goal is to teach you how to become more self-sufficient, no matter how small the change.

Please feel free to reach out to me with any questions or comments.

Have a great day!

Regina Ferrari


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  • 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!

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