Living off grid doesn’t have to mean sacrificing modern-day creature comforts like hot water. However, deciding on the best off-grid water heater depends on:

  • Your personal needs
  • Energy source
  • Geographical location. 

We’ve reviewed the best in each category based on their purpose, energy source, and efficiency to provide detailed insights so you can make the best decision for you and your family. 

Top Pick

Rinnai V75iP Water Heater

The Rinnai V75iP is the best all-around off-grid water heater to meet the needs of your entire household. It features 7.5 GPM, 140-degree water temps, and 180k BTUs. 

Off-Grid Water Heater Reviews

Best Overall: Rinnai V75iP LP Indoor Tankless Water Heater


  • Type: Propane
  • Power: 120V
  • Gallons: Tankless
  • Location: Indoor
  • Weight: 47.4 lbs

The Rinnai V75iP 120V tankless water heater is a great whole-house, off-grid system that’s super energy efficient and provides maximum output. Rinnai touts that its tankless water heaters last twice as long as traditional tanks and use 40% less energy. Plus, their on-demand hot water means no waiting. 

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However, because this is an indoor unit, it does require ventilation. Choose between standard, horizontal, or concentric venting. You’ll need Rinnai’s own proprietary venting kit

The Rinnai V75iP pushes 7.5 gallons per minute and can run five faucets simultaneously. It reaches temperatures up to 140 degrees with a maximum output of 180,000 BTUs. The unit features a Wi-Fi control (purchased separately) and can be paired with an external pump to reduce wait time. 

Be advised, however, this unit is equipped with an electrical ignition and therefore requires a 120V plug. It is only suitable for homes that have access to off-grid electricity. 

Rinnai recommends you have the system installed professionally, but plenty of people have installed this system on their own. A word of warning: Many users report installation difficulties and a lack of technical support.


  • Easy to use
  • Precise temperature settings
  • Small and compact
  • Leak detection shutoffs
  • Isolation and pressure-relief valves 


  • Professional installation recommended
  • Proprietary vent system
  • Needs 120V electrical outlet

Best Outdoor: Rheem 8.4 GPM Outdoor LP Tankless Water Heater


  • Type: Propane
  • Power: 120V
  • Gallons: Tankless
  • Location: Outdoor
  • Weight: 54 lbs

The Rheem Outdoor Tankless provides continuous, nonstop water for three faucets at a time. This unit is an excellent option for homes with 2–3 bathrooms. It features a .26 gallons-per-minute, low-flow activation and can provide up to 8.4 gallons per minute throughout your home. 

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There’s a wired remote digital display for precise temperature settings up to 140 degrees with a maximum output of 157,000 BTUs. The Rheem Outdoor Tankless also features detailed diagnostics when service or maintenance is required. 

The Rheem LP Tankless allows for expansion—you can couple numerous units together with EZ link cables. Because this unit is mounted outside, no venting is necessary. 

Like the Rinnai, this unit requires a 120V outlet for its electrical ignition.

Professional installation is required unless you want to forfeit your warranty.


  • Super easy installation
  • Freeze protection to -30 degrees
  • Overheat protection
  • Ultra LoNox
  • Self-diagnostic system
  • Allows for expansion


  • Needs 120V outlet
  • Takes longer to heat water
  • Loss of warranty with self-install

Best for Small Spaces: Marey LP 2.64 GPM Tankless Water Heater


  • Type: Propane
  • Power: D batteries
  • Gallons: Tankless
  • Location: Indoor
  • Weight: 22 lbs

The Marey Liquid Propane Tankless Water Heater is a great option for smaller off-grid cabins that don’t have access to a power source. One of the best features of the Marey is that it uses zero electricity to operate. 

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Simply attach your inflow, outflow, and propane, and you’re all set. A minuscule amount of .66 gallons per minute ignites the pulse ignition via two D-cell batteries. 

The Marey Tankless features an oxygen-free copper heat exchanger for increased efficiency and twin solenoid valves for increased safety. It pushes 2.64 gallons per minute and has a max output of 68,240 BTUs.

There are three control knobs on the face of the unit to control flame height, water flow, and the number of burners. 

There is no direct temperature control with this unit. Instead, the water temperature is adjusted using these knob combinations. More burners, higher flame, and less water flow increase the water temperatures.

The Marey LP Tankless design functions with your current plumbing, so it can easily replace a traditional water heater. Because it is an indoor unit, a Z-vent is necessary for exhaust, which you can install through the wall or roof.


  • No electricity required
  • Water-flow activation
  • Automatic shutoff
  • Overpressure protection


  • Not recommended for elevations >2000 feet
  • No direct temperature control
  • Only good for small spaces

Best Solar: Northern Lights SunRain 20 Tube Solar Vacuum Water Heater


  • Type: Solar
  • Gallons: 80
  • Location: Outdoor
  • Weight: 260 lbs

Northern Lights provides pre-engineered, DIY solar water-heating solutions. The SunRain solar system is a cost-effective strategy for heating water off grid and is best for those with a private well. The system can be mounted on pitched or flat roofs or on the ground. 

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This compact solar water heater is a pressurized system and requires up to 60 psi to push water through. As the vacuum tubes heat the water, it flows from the tank directly to potable water. The pressure from your well pump then pushes the cold water into the vacuum tubes to be reheated. 

The system features a built-in air-release valve and a temperature and pressure release valve that opens at 194 degrees F to prevent overheating. 

To maximize efficiency, SunRain uses Northern Lights’ proprietary “3-Hi” vacuum tubes for heat absorption and an added aluminum-copper layer for heat conduction. An additional solar water heater acts as an all-in-one pre-heat tank, combo electric tank, and dual heat exchanger tank with less than .8 degree temperature loss per hour. 

Additionally, it features a 4.5 kw 240V backup heating element. 

Northern Lights offers pre-packaged systems with RESOL controllers, pump stations, and remote access capabilities. 


  • Cost-effective
  • All-in-one system
  • Passive freeze protection
  • Maintenance free
  • No electricity required


  • Expensive start-up costs
  • Requires pressurized water
  • Dependent on sun

Best Wood Burning: Lehman’s Wood-Fired Water Heater


  • Type: Wood
  • Gallons: 15
  • Location: Indoor/outdoor
  • Weight: 235 lbs

Wood-burning water heaters are the most cost-effective solution if you have the wood to support them, but hovering around 70%, they’re also the least efficient. The trade-off is Lehman’s wood-burning hot water system allows you to be totally off grid, requiring only wood and labor.  

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There are no added costs for solar panels, battery banks, propane, or natural gas. If you don’t mind the labor, and you have the wood to burn, Lehman’s wood-burning hot water system provides you with total self-reliance.  

Its highly durable 3/16″ welded steel holds 15 gallons of water that completely surrounds a 2.4 cubic foot firebox that can hold up to 26″ logs. It features a 1″ female iron pipe tap (FIP) on the bottom for incoming water, and an outflow FIP on the back. It also features a draft-controlled door and needs a 6″ flue for installation. 

Bear in mind, however, that maintaining any wood-burning water heater poses its own challenges from starting the fire to maintaining the temperature. But if total freedom is what you seek, then you can’t go wrong with this wood-burning option.


  • Cost-effective
  • Extremely durable
  • Completely self-reliant


  • Less energy efficient
  • Labor intensive
  • Difficult to manage

Best Portable: GASLAND Outdoors 1.58GPM Portable LP Water Heater


  • Type: Propane
  • Power: D Batteries
  • Gallons: Tankless
  • Location: Outdoor
  • Weight: 15.27 lbs

The Gasland Outdoor Portable Water Heater is ideal for those who enjoy life on the go. They’re great for hunting cabins, overlanding, quick outdoor cleanups, and power outage backups.  

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Designed for 20-lb tanks, simply connect your propane bottle and your garden hose, and you have hot water. It has a pressurized electronic ignition powered by two D-cell batteries and must have a minimum of 3.6 psi to start. 

Once ignited, you can view the flame through the flame-viewing window. It also features an adjustable digital temperature display. 

It has many safety features, including anti-freezing, low flow, overheating, dry combustion, and high-water-pressure protections. The system comes complete with a gas regulator, showerhead, NPT (National Pipe Taper), and GHT (garden hose thread) adapters. 


  • Portable
  • Battery operated
  • 41,000 BTUs
  • Quick and convenient


  • Max temperature of 109°F
  • Must be drained after each use
  • Not suitable for high altitudes 
  • Not for everyday use

Best Emergency Use: 4Patriots Sun Kettle


  • Type: Solar
  • Gallons: 16.9 oz
  • Location: Outdoor
  • Weight: 2.65 lbs

If you’re just looking for something simple to use during an emergency, then the Solar Kettle Pro is your go-to option for power outages and natural disasters. Small enough to fit in your bug-out bag, it can bring just over one cup of water to 212 degrees in approximately 45 minutes. 

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Fully powered by the sun alone, it does not require batteries or electricity to function. Simply fill it with water, open the panels, and set it in the sun until it reaches your desired temperature. 

There’s much debate on whether or not the 4Patriots Sun Kettle actually heats water to boiling or not. Such a feat likely mandates the most perfect of days. 

However, in a pinch, it’s a great option for a quick bite to eat or a little warm water for bathing and hygiene. At the very least, it’s good for a hot cup of coffee. 


  • Needs only sun to heat
  • Heats to 212 degrees
  • Good for emergency use


  • Not for daily use
  • Extremely small capacity
  • Takes a long time to heat

Choosing the Right Off-Grid Water Heater

When choosing the right water heater for your off-grid location, there are several factors you should consider.

Water Usage

Likely the most important factor is the amount of water you need to heat on a daily basis. A full-time residence has much greater requirements than the occasional weekend getaway. 

The average person uses just over 13 gallons of hot water a day. Multiply this by the number of people in your household to get an idea of how much hot water your family needs on an average day. 

For water heaters that use tank storage, the higher the number, the larger the necessary capacity. For tankless water heaters, the higher the number, the more peak flow is required. 

Additionally, the amount of water used directly impacts the amount of propane, wood, or other heating source you’ll need. 

Indoors vs. Outdoors


Here’s what you need to know about indoor units:

  • Work best with new construction projects
  • Require venting
  • Less expensive than outdoor models
  • Better option for colder climates 

If you’re considering an indoor tankless water heater for your existing home, you should know they often require modifications for your current water and gas lines in addition to very specific venting requirements, not to mention condensation outlets. 


If you’re thinking about an outdoor tankless water heater, consider the following:

  • Frees up living space
  • Doesn’t require venting
  • Works best in warmer climates
  • More expensive than indoor models

For more detailed decision-making factors, here’s a nice summary video covering everything to consider when it comes to tankless water heaters.

The Right Size

To determine the correct size for your indoor/outdoor water heater, you must determine the peak hot water demand. This is a hypothetical number providing the maximum amount of water that you need at any given time.  

For example, if you were running all of your faucets, your dishwasher, and your washing machine at the same time, how much water would it require? You also need to contrast that information with your outdoor water temperatures and the necessary temperature rise required. 

If unsure, this article can help you calculate your temperature rise and peak hot water demand.

After you add it all up, your water heater should align with those numbers to meet the demands of your household. 

Calculating Costs

When selecting an off-grid water heater, additional costs play an important factor. Many people choosing an off-grid lifestyle select propane as their heating source, but with that comes an added expense. 

You need 650 BTUs to heat one gallon of water through tankless propane heaters. If the average person uses 13 gallons of hot water daily, you need roughly 8,450 BTUs for each person in your household. 

A 20-lb propane tank contains approximately 430,270 BTUs at 60 degrees. So your propane consumption might look something like this:

No. of People BTUs Required Total Usage Number of Days
1 8450×1 430,270÷8,450 50.9
2 8450×2 430,270÷16,900 25.45
3 8450×3 430,270÷25,350 16.9
4 8450×4 430,270÷33,800 12.72

It goes without saying the larger your family, the more propane you need and the faster you go through it. Likewise, the longevity of your propone significantly decreases if your outdoor water temperature falls below sixty degrees. It’s important to weigh the costs of propane and how it fits into your budget.  

While solar models are definitely more expensive at the outset, over time they may save you a tremendous amount of money. Plus, they make you a little more self-reliant.

Energy Types

Aside from traditional electricity, there are essentially three different types of off-grid energy sources, and each has its advantages and disadvantages. 


Although it’s an added expense, propane has great features for off-grid use:

  • Portable
  • Cheap
  • Easy to use 

However, if you have a larger family, the expense can add up. Propane also struggles to burn well during colder weather. 

You also have to retrieve it or have it delivered, which is an additional expense. Furthermore, it’s certainly not out of the realm of possibility to one day find it in short supply. 


While solar heating is absolutely free, the initial start-up costs are not. Getting a solar system up and running is quite expensive, but over the course of a lifetime can be substantially cheaper. Solar also has advantages for off-grid use:

  • Free hot water
  • Little to no maintenance
  • Possible tax credits

Unfortunately, solar is less efficient in colder climates. 


Finally, if you have the acreage and the wood to burn, then a wood-burning water heater offers many advantages:

  • Cost-effective 
  • Free fuel for heating
  • Completely off-grid

The downside is that wood-burning water heaters are less efficient, labor intensive, and require more maintenance.


Finding the best water heater is not always an easy task, but with a little forethought, you can match the best design to fit your personal needs. If you have access to 120V, the Rinnai V75iP is an outstanding option to provide all of your hot water needs.

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