Tiny House, Tiny Living, The Tiny Life.

Choosing A Hot Water Heater For A Tiny House

Recently I have been spending a lot of time trying to figure out the best option for hot water heaters for my Tiny House, but I have been back and forth on which way to go.  So I realized, why don’t I see what my readers might know!

So far I have decided to focus on tankless hot water heaters.  Essentially these hot water heaters don’t hold water like traditional hot water heaters, they rapidly heat the water as it flows through their heat exchangers so you only heat the water you use.  The area I am having trouble with is to go with an electric unit or go with a propane unit.  I don’t like how much power the electric ones use (13 kw/h) if I one day go solar, but the gas units are a lot bigger (not so great in a tiny house) and need to be vented.  I also don’t know how quickly I would burn through a propane tank (I take 10-15 minute showers daily).

 

Your Turn!

Do you have a tankless hot water heater, how do you like it?

How do you plan to heat your water in your tiny house?

32 Comments
  1. Using electric is a massive amount of power. The value of electric on-demand water heating is in the fact that there is no idle heat lost from a hot water tank. In a tiny-house, I would expect that most people (certainly me) will not have that kind of power on demand. Using the 13KW model you mentioned, that translates to a 13KW generator (with nothing else loading it down) for anyone off grid. That’s a big generator! If you have an electric hookup that still translates to ~60 amps (again, not counting any other loads). Most RV hookups are 110V at 30A, which is a little over 3,300W. Around 1/4 of what you need to power it.

    So, in my opinion, unless you plan to have some serious power (and non-standard higher amperage power connections on your tiny-house, as wells available to plug into) then the electric one is not even an option in my mind.

    There is my $0.02 worth of thoughts. :-)

    -Michael

    • Very good points! I will be grid tied for the most part, I keep getting hung up on the size and the cost the 13 kw/h electric one I can get for $180 and is the size of a large text book. The Gas is around $1300, and is 24″ x 17″ x 10″ then you have to vent it.

  2. My family has been using the EccoTemp tankless propane water heater DAILY for over a year, and we LOVE IT! Very easy to use, sturdy, heats up water immediately, and has adjustable settings to make the water just right, no matter how warm you like it. And the best part, it’s very inexpensive! It takes us about 6 months to run through a small tank of propane, used exclusively for the shower, and that’s a family of 4!

    The only additional advice I have is to make sure that if your tankless is installed outside (which this model has to be), you use chicken wire or some other type of wiring to keep critters out of the heater. One morning a snake had slithered into the top of the heater, and I didn’t see it until he was cooked by the flames. Not a pleasant smell! But, in testament to the sturdiness of the product, even burning an entire snake inside it did not affect the function of the unit!

    • Jennifer,

      What climate are you in? When you say a small tank do you mean the 20lb tanks that most grills use?

      One thing that I read about the ones outside is you have to be careful about people stealing it for scrap metal.

      Ryan

    • I have been considering EccoTemp but I can’t find the specs on flow rates for the rise in temperatures.

  3. I have propane instant-on water heat here. With two people taking showers, each twice a week or so, it took almost a year to go through a tank. I use propane for the oven/stove too, but only once or twice a week for a few minutes at a time for that. Don’t cook much… :)

    Propane, definitely :)

    You could maybe get a smaller unit if you look around.

  4. Perfect! The hugh tanks you see in closets and garages in homes all over the USA are obsolete and have been for 30 years. We’ve had our instant water heater installed in the early 80′s. It runs off of propane. Unbelievable! the water is super hot immediately!so be careful. We all are used to turning the knob in the shower all the way to hot to allow the water to heat up. Big mistake here, with these powerful little heaters the water will be HOT immediately! I use less water today to shower and our bill is relatively nothing in comparison to what our neighbors pay. I plan to install solar soon. Not only is the small heaters ideal for tiny homes, if you live in a regular sized home, convert your prehistoric water heater and install a small unit like the one presented in the artical. You will save lots of $$$ and water too. If you have children they could be scolded immediately! if not supervised. Remember, there is no wasted water just a learning curve :)

  5. I too would reccomend a gas unit. If you really want to go completely self reliant, You can still work with a methian bio-digester. In the mean time to be off grid with such a unit would require by my estimate at least 2K of solar power, which averages a $1/watt if you shop really well. In addition, I have never found an off grid inverter larger than 5KWatts, about 1/3 of what you would need. From a 12V battery bank, you’ll still be pulling 1080 Amps, which is a massive amount, requiring massive cables. There are a few grid tie inverters that can handle about that much, but I don’t believe they work without the grid connection, and they are still more than $6000 dollars.

    As has already been mentioned, there are no commonly available RV hookups which can take that much power. You’ll need something specially made. If you do have it, at least put it on a completely seperate cicuit from the rest of your home, preventing you being knock off due to no proper connector.

    • A more attractive option may be a tankless water heater designed for an RV. They are generally made to be mounted on the outside wall, and thus are self ventilating. They are generally smaller too, and cheaper too, around $600 or so.

  6. Hi:
    I have used gas demand or tankless hot water heaters since 1983.Initially a Paloma from Japan for a 14×14 cabin in NW Montana mountains. That LP model lasted for over 20 years until the hard water thinned the walls of the water circulation tubes surrounding the burner. The pin hole leaks salted in on their own but reappeared within two years requiring replacement of the tube unit.

    When I moved to S.California I installed a small NG[natural gas] Bosch Aqua Star tankless Model GWH 1000-P in the “enormous” 450 square foot house I now rent. It cost $300 in 2009. It is perfect for this house because the water lines have short runs so less heat loss from the pipes which are foam wrapped for insulation purposes.The climate is very benign with only rare temps below freezing.In Montana I chose a larger model to balance the cold water input with more BTU’s.

    Dimensions:22.8″H x 12.2″ W x 8.6″ deep; Weight 26#.
    Capacity:2.6GPM
    Min-Max Output:24000 to 58400BTU’s
    Vertical natural draft venting via 4″ pipe to 6′ height
    Indoor installation for this model. Other choices include Rennai,Paloma and larger Bosch models.
    I hope this information is useful for your project.
    Persevere,
    Don

    • Great in Don! What are the overall dimensions of the unit you have including the hook ups and the venting? I am trying to fit this under a counter top.

      • Ryan:
        These units should not be enclosed in a cabinet indoors. They need airflow to function properly. They require substantial air gaps from combustable surfaces along all but the back side surface. CO and CO2
        Do you have freezing temperatures for long periods where you will be building? As I understand it, most smaller tankless models are not designed for sustained freezing temperatures.But RV models like this:[http://www.rvshop.com/Tankless-Water-Heaters_c_1986.html] have a winterizing system. Also see: http://www.rvdoctor.com/2011/07/choosing-tankless-rv-water-heater.html

        One alternative is a wood stove with a waterjacket tank for water heating. Unfortunately it will not meet your 15 minute hot shower requirement! Or: http://www.dickinsonmarine.com/propane.php

        I have no experience with electric point of use heaters which are cheaper to buy but more expensive to operate via your electric bill. With your access to line power it might be worth an experimental test.
        I hope the rambling answer is useful.
        Don

        • I have been looking at RV doctor, the RV-500 might be my choice, I need to give them a call for some more specs on the unit. As for enclosing it in the cabinate, I would be sure to maintain clearances and the venting would go through the exterior wall.

  7. Really interesting question! I had no idea you needed so much electrical power to run a tankless water heater. I wasn’t planning to install propane, but now I’m rethinking…

    What about something like this? http://www.amazon.com/dp/B0030GHCT8/?tag=hyprod-20&hvadid=15467976219 It’s an indoor propane tankless water heater for only $429.00. It’s 4 x 17 x 8 inches, and 34 pounds, with a flow of 6.3 gallons per minute since it’s designed to work for the standard three bedroom, two bath house.

    • Cheryl,

      Thanks for pointing that one out! You do have to watch out with the GPM flow rate as it is effected by the amount of temperature rise needed. This one can do 6.3gpm at 35 degree rise and 2.6 gpm at 70 degree rise; all of which would exceed my needs, so it has made the list!

      Ryan

  8. I’m assuming that the propane ones heat a tank of water when you turn them on?

    So they could wind up like a wood chip heater (http://en.wikipedia.org/wiki/Chip_heater) as an alternate source of energy if you don’t want to do a propane one.

    Are the electric ones more like an instantaneous hot water system? Where the water passes from a storage tank (or mains supply) over a heating element directly into the hot pipes/shower? Because we’ve had issues with low water pressure not actually working well with those – there wasn’t enough water pressure to actually create a hot enough shower.

  9. We are in the early stages of planning our tiny house that will end up in Northern Minnesota. Are there any concerns with externally mounting a self-venting propane unit in a climate where temperatures routinely go well below zero?

    • The two things that I can think of is the aesthetic impact and then also less than honest people looking for scrap metal to sell for quick cash.

  10. I think you must have a pressurized system for the unit to work.

  11. I am also in the process of designing and also looking at water heaters, if you are still looking for a reasonable 120v water heater that only uses 25 amps this may be the one, I have found a few good reviews!
    http://www.amazon.com/Stiebel-Eltron-DHC-3-1-Electric/dp/B001AHQ9C0
    Be aware you have to have very low water flow for this one to work for you, I hope that helps your search.

  12. Safety mean
    s no gas… Here in Europe there are small 3.3 kW 220V instant waterheaters which give about 3 liters per minute 45 °Celsius water. The unit is damn small, easy to install and cheap too (around 120 dollars up).

    By the way, marine-showering costs less water, less power and is ecofriendly too, no need for spoiling drinking water for 15 minutes per showersession!

  13. I happy to have stumbled-upon this site. So far, I’ve read some great pointers into the vast world of small dwelling/RV water heaters. We are searching for the best off-grid compact water heater for our caravan home.
    The original water heater was rusted and old when we bought our place, so the space is empty and wouldn’t be too hard to fill. Prior to reading this article, I was shopping for an electric Point Of Use Water heater. But after reading the advice of folks who have been there and done that, I am rethinking…and researching propane models.
    But I was wondering… Does anyone know if there is a combination electric/propane model? That, to me, would be great as long it was still compact.

    Blessings!

    Penny

  14. Ryan or any other wanderer,
    Which did you ultimately go with? I’m leaning toward a gas heater but how much more intimidating is this the install for someone with no experience? Also, for off grid do people usually install some type of 300 gallon drum with rain water run off capabilities? We will be traveling about every 3 months and would like the ability to stop at rest areas but still be able to shower, etc. any good websites youc. Any suggest for off the grid living solutions?
    Thanks

    • I ended up with the RV-500 by precision temp

      • Hi Ryan! Read all your postings here with great interest… Myself and my family were all set on purchasing a Rinnai Tankless system but were disuaded by our plumber, stating, we would draw so much fuel that the smaller tanks just can’t handle it without causing freezing issues. What part of the country do you live in? Can you do a review on your RV500? Cheers!

  15. I think there is some miss understanding around the electric version from Rheem. The unit uses 13 kW which is to say 1300 watts, or roughly 10.5 amps, at 120v. If you ran it on 220 that would drop to 5 amps.

    All the best.

  16. I am afraid of anything with propane. What are the final thoughts on the best electric off grid using solar energy.
    Thanks

  17. Also, I like changing from cool water to warm /hot water. How does that work when in the shower. Also, do not take longer than about 5 minutes in the shower.
    Thanks

  18. interesting read, to people not used to propane or natural gas check all connections with soapy water bubbles means leak. and equip your home with a carbon monoxide detector if you burn any fuels. cheap insurance that you wake up in the morning

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