Which Tiny House Water Heater Should I Buy? Advice From A Full Time Tiny Houser

tiny house hot water heatersIf there is one thing I love about my tiny house, it’s the tiny house hot water heater I currently have. After living in my tiny house for over 7 years, I’ve actually gone through a few tiny house water heaters, but there has been one that stood out from the rest. I’ll get to that soon.

My Top 5 Tiny House Hot Water Heaters:

Precision Temp RV-550 Eco Temp
Eco Temp
Rinnai V53DeP Precision Temp RV-550 Eco Temp L5 Eco Temp L10 Rheem RTEX-11
My Ranking
Flow Rate 5.3 GPM 1.5 GPM 1.5 GPM 2.9 GPM 2.68 GPM
Energy Type Propane/Natural Gas Propane Propane Propane Propane
Why Consider Best performance and build quality Good option for 12-volt systems Great for outdoor showers Budget friendly with good functionality Super compact
Who Is It Best For General and off-grid water heating RVs Weekend cabins and seasonal outdoor showers Budget-minded tiny house folks Those on the grid
Price $550 $1,195 $129 $349 $275

tiny house hot water heater comparison

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Rinnai V53DeP

Rinnai V53DeP hot water heater

Rinnai V53DeP
Rinnai V53DeP
My Ranking
Flow Rate 5.3 GPM
Energy Type Propane or Natural Gas
Why Consider Best power and build quality
Who Is It Best For General and off-grid water heating
Price $550

I mentioned that of all the tiny house hot water heaters I’ve had over the years, there was one that stood out, and this was it. Rinnai has been in the tankless hot water scene for a very long time. Way before most of us even heard of this company, they were building hot water heaters.

I think it’s very telling that every time a plumber has come to my house (not to fix the water heater), they always say something to the effect of “that’s a great choice” or “Rinnai is the best for tankless”. After using my V53 for close to 5 years, I have to emphatically agree.

You can order these units in a propane version (denoted by the P at the end of the model number) or in a natural gas version (N model). This is a direct vent style that is made to mount outside your tiny house, which is very important. Venting is a huge pain in a tiny house because you need to use such large ducting. It’s much easier to just mount it on the outside.

These units have freeze protection and you can buy an optional dump valve if the power goes out. This is the best option for an off-the-grid hot water heater that I’ve found. Running on propane is easy. I just have normal 20 lb. propane tanks hooked up to it and can heat my water and cook on my stove (also propane) for about 2-3 months per tank.

At 5.3 gallons per minute (GPM) this will give you endless hot water even if you have a shower going and two sinks. These units come in at around $550 and it’s money well spent. These units are built to a very high standard, in my experience.

Precision Temp RV-550

Precision Temp RV-550 hot water heater

Precision Temp RV-550
Precision Temp RV-550
My Ranking
Flow Rate 1.5 GPM
Energy Type Propane
Why Consider Good option for 12 volt systems
Who Is It Best For RVs
Price $1,195

I put this one next because I know it’s a very popular water heat for tiny houses. However, I’ve had three of these now and each one of them was plagued with issues. At a price of $1,195, there is no excuse for it to not work well when it’s already twice the price of the next most expensive competitor.

I’ve detailed why I don’t recommend this company for tiny house hot water heaters in this post. The biggest issue I had was when I received my first unit, I noticed an odd rattle inside it. I decided to open it up, only to find the internal vent loose, so all the carbon monoxide created by the unit would have blown right into my house instead of venting outside. That could have killed me.

Now there are some reasons that people like these units. First off, it’s designed for RVs and campers, so it can handle lower flow rates than some of the competitors. At 1.5 GPM this will be able to run a low flow shower head or a sink, but not really both at once.

Another thing to know is that this unit doesn’t have the same BTUs as the other units. My Rinnai has a max BTU output of 120,000 BTUs, while the RV-550 only has 55,000 BTUs. What that means in practical terms is that in my mild winters in North Carolina, the best the RV-550 could do was make my water warm, but not hot.

To be fair, Precision Temp is very transparent about this, but I didn’t understand what 55k BTUs really meant practically even after reviewing their site and literature.

So to sum up, it’s twice the price, half the BTUs and, in my experience, workmanship on these units is not acceptable.

Eco Temp L5

Eco Temp L5 hot water heater

Eco Temp L5
Eco Temp L5
My Ranking
Flow Rate 1.5 GPM
Energy Type Propane
Why Consider Great for outdoor showers
Who Is It Best For Weekend cabins and seasonal outdoor showers
Price $129

This is another very popular tankless hot water heater that many people consider when thinking about building a tiny house. I actually recommend this to a lot of people… In very specific circumstances. I think if you use this hot water heater in the right case, you’ll love it. But if you try to do something it’s not really meant for, you’ll be disappointed.

This hot water heater is designed for those who need hot water in more remote or austere conditions: your weekend rustic cabin, going camping, setting up a temporary shower or if you need hot water in some remote part of your property.

This unit is designed to be used seasonally with less-than-permeant usage.

What that means is if you have this as your main tiny house hot water heater, you’re going to be disappointed. It’s an attractive option at $129, but for everyday use, you’ll want something more robust.

What I use this for is my outdoor shower. I’ve used the L5 for years now as an outdoor shower and it’s amazing for that. I have a simple platform I stand on and I mount this unit on a single screw on a vertical post. I connect my garden hose and a 20 lb. propane tank and in literally 2 minutes I am taking a nice, hot shower.

For the price, this unit is a great buy. One downside I’ve found is that if there is any real wind, the unit’s flame will go out. You can do some shielding around it, but because this unit is a direct vent unit, you need to keep it outside — never bring it inside!

Eco Temp L10

Eco Temp L10 hot water heater

Eco Temp L10
Eco Temp L10
My Ranking
Flow Rate 2.9 GPM
Energy Type Propane
Why Consider Budget friendly with good features
Who Is It Best For Budget minded tiny house folks
Price $349

If you’ve considered the other Eco Temp model but want something that’s going to be more reliable for your house in everyday use, this is a great option. The L10 is designed to be used on a house for everyday use at 2.9 GPM, where the L5 is more for camping applications.
At $349, this strikes a very good balance of cost vs. value. I’ll be upfront and say that this company is a lower-tier manufacturer from China relative to Rinnai, but I’ve found they do a good job for the price. While you can see the products are no frills, they do a decent job with the important things.

The biggest difference between this one and the Rinnai is that the heat exchanger on this unit is made of less copper. You can see that this heat exchanger is silver in color from the different (cheaper) alloys used to make up the most important part of the unit. The Rinnai uses high-quality copper in it, which makes for a better product, but copper is much more expensive.

This one is also an outdoor mounted version, so venting is a breeze and it also runs on propane, which I find to be the easiest fuel source.

Rheem RTEX-11

Rheem RTEX-11 hot water heater

Rheem RTEX-11
Rheem RTEX-11
My Ranking
Flow Rate 2.68 GPM
Energy Type Propane
Why Consider Super compact
Who Is It Best For For those living on the grid
Price $275

The last option here is the Rheem RTEX-11, and this is one that I looked at seriously for my tiny house. The biggest benefit of this unit is that it’s so compact — only 8 inches wide x 13 inches tall x 4 inches thick. That’s about a tenth the size of all the others on this list.

The reason for that isthat Rheem units use electric to heat your water. This unit comes in 8, 11, and 13 kilowatt versions. The 8 KW version might be a little too small for your needs, while the 11 KW version would be perfect for tiny houses at a flow rate of 2.68 GPM. One benefit to electric models is that you don’t have to vent, so this unit can be tucked under your counters, back in a corner of your cabinets.

If I was able to be on the grid, this would be the unit I’d have gone with. A lot of the plumbers I talked with said Rinnai was their personal favorite, but Rheem was a close second. Being that I live off the grid, I have to heat my water with propane.

It is also hard to beat the price at $275. With this high quality of a unit in such a small housing, this is a great hot water heater option for your tiny house.

tiny house plumbing

Tiny House Water Heater Buying Guide

Tiny House Water Heater Buying Guide

Choosing a hot water heater for your tiny house is an important decision because it will impact your designs, utility connections and if you can go on or off grid. Hot water is also one of those hallmarks of civilization if you ask me, nothing is better than taking a long hot shower.

Here are some things to think about when choosing a tiny house water heater:

Tankless Vs. Traditional

Tankless Vs. Traditional hot water heaters

Let me make this simple: you want tankless. Traditional hot water heaters have large tanks that hold water and heat it constantly. Not only is this pretty inefficient because you’re heating water when you aren’t using it (which is most of the time), but these are also very heavy.
Water is about 8.2 lbs. per gallon and in a tiny house, every ounce matters. Having a traditional water heater means you need a much bigger trailer, and that adds up fast. Along with weight, traditional water heaters are also much larger, which isn’t ideal in such a small space. Tankless hot water heaters typically take up a lot less space, making it easy to mount in a corner under a cabinet or on the outside of your house entirely.

Tankless hot water hearts are also a huge step up over tanked hot water heaters because you can never run out of hot water. The price of traditional models isn’t that much cheaper either, so the cost versus benefit of tankless is a clear winner.

If you want to be off the grid, tankless running off of propane or natural gas is really the only practical method unless you use a wood stove, which is a real pain.

Indoor Vs. Outdoor Installations

hot water heater Indoor Vs. Outdoor Installations

This is another simple decision: outdoor installation is ideal. Indoor mounted hot water heaters require you to vent them with vent tubes. These tubes are pretty hefty and mean you have to cut a large hole in your wall to vent properly.

Compared this to an outdoor installation that you can vent right outside with no extra work involved. Mine mounted in about 5 minutes and the vent was already built into my unit, so I couldn’t screw it up if I tried.

Indoor units can be tricky to vent, requiring certain offsets and maximum vent lengths that are shorted by each elbow you put in the vent tube. The only time I’d opt for an indoor mounted unit is if I lived in a place that was prone to super cold temperatures.

Between the ease of installation and the fact that you aren’t taking up any indoor space, I’d suggest an outdoor mounted tankless hot water heater.

Energy Source: Propane Vs. Natural Gas Vs. Electric

Propane Vs. Natural Gas Vs. Electric

This really comes down to if you want to be off the grid or not. If you’re going to be off the grid or might be some day, propane or natural gas is the way to go.

If you’re going to be in one spot and have a gas delivery truck fill up a larger tank, natural gas is most likely the way to go. If you’re on the go or just getting your own gas, I’d suggest propane because it’s more readily available.

If you’re on the grid, the electric models from Rheem are really nice and super compact, plus there are no gas lines to mess with — a bonus in my book since running gas lines can be dangerous and always makes me nervous.

Off-Grid Hot Water Heating

Off-Grid Hot Water Heating

Much to my point above, if you’re going to be off the grid, a gas option is really your best bet. I crunched the numbers on what it would cost to add additional solar panels to my system to offset the need for propane and it was going to cost me an additional $15,000 just to have an electric hot water heater.

I like to keep in mind that my house is totally off the grid, running on solar power, so I’m already treading very lightly on the earth. If I use 80lbs of propane per year, I’m still much better than most out there.

Many people ask about heating their tiny house and their water with a wood stove, but my advice is to avoid this unless you already live with a wood stove that is your primary source of heat. Wood stoves are often romanticized by people when designing their tiny house. The reality is that you’ll be waking up to a pretty cold house each morning, hot water won’t be ready for at least an hour, and it doesn’t heat much water to begin with.

Go with a gas option for heating water off the grid — you’ll thank me later.

solar power for tiny houses

Hot Water Heater Venting

Hot Water Heater Venting

If you have a hot water heater that is installed inside your tiny house, you’ll need to vent it if it uses any form of combustion. Venting isn’t something to take lightly because there are so many ways to do it wrong and mistakes can lead to deadly results.

Vents are usually metal ducting that captures fumes and exhaust from your hot water heater and directs them outside. They may also have an air inlet to bring in fresh air for combustion.

Venting usually has a lot of technical parameters from the manufacturer around how far the vent tube can stretch, the type of ducting you use, offsets or clearances from combustibles materials, and other technical bits to make sure you do it right.

I prefer to have outdoor mounted hot water heaters because it avoids all the headaches and potential dangers. If you do decide to use a unit that requires venting, follow the manufacturers directions carefully.

Preventing Freezing

Preventing a hot water heater from freezing

Another area that you can go wrong with hot water heaters in a tiny house is having pipes freeze. Most units today have some sort of frost prevention mechanisms, usually a heating coil for outdoor mounted units. Indoor mounted units don’t really have to worry about this.

If you live in a very cold climate, indoor mounted options might make a lot of sense, even if it’s an indoor mount in an unheated enclosure that’s been insulated well. The best advice I’d say is to follow local wisdom on how to prevent freezing.

You want to try to minimize the PEX lines outside your heated space and, where possible, insulate and apply heating strip tape to them for frost prevention.

Your Turn!

  • What are your plans for your tiny house hot water heater?
  1. I’ve been living F/T in my THOW (in the Athens, GA, area) for almost four years. I’ve had a Marey hot-water-on-demand unit & have been VERY happy with it. I can’t recall all of the specifications for it, but I’ve never had a problem with showers or kitchen sink hot water. I’m on-grid but eventually would like to have solar panels installed, which would make me even happier.

  2. Our tiny house in Bozeman MT had a propane fired Precision RV 550 that froze, even with an incandescent light bulb as heat source in the chassis of WH. Bozeman gets real cold in winter. Local RV repair person told us that he does not suggest them in that cold climate (several dead ones in his yard). Now that we have a hole cut in the side of our house (for the inset water heater) and we do not want to have anything projecting on outside, any suggestions what propane heater to use that can take very cold temperatures?

  3. Every quiz I take points me to a van conversion (I’m thinking some sort of box truck). One of the things I like about them is the “stealth” option — i.e. living on city streets without drawing attention. Not sure what a hot water heater mounted on the outside of the truck would do for that. Also, could it be stolen?

    • Hey Amy,

      Yes that is a real possibility. They do sell ones that you can mount inside and vent it out. Might be more discreet and secure

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