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So you want to make the switch to a tankless water heater? But maybe you just don’t have space, or don’t want to perform the renovations needed to fit an indoor unit. Fear not, there are outdoor units for nearly every major tankless heater model on the market.
But what’s the difference? The main thing is that they are installed outside(of course), meaning their ventilation is outside. That means you can avoid the running of ventilation pipes through your roof, letting the gas naturally disperse itself into the air for propane models.
It also saves you space, since while these products are smaller, they still need a somewhat out of the way space to sit and do their work.
So what do we look for in an outdoor unit?
9 Best Outdoor Tankless Water Heaters of 2019
Another of the relatively rare mobile home certified units, this one is sort of like a stronger (but more expensive) version of the V53 from the last entry.
Unlike the V53 though, this one can actually handle the colder weather, and has a much high heat output at 150k BTUh and a higher flow of 6.6 GPM, though that will as usual dip the colder your groundwater is.
For those in a mobile home in colder weather, this is the unit. While the V53 edges it out in warm weather simply for being cheaper and nearly as effective, this is the one to beat for mobile homes (and none on this list beat it), and coming in just under $700 means it’s not too hard on the wallet.
The main downside is its size, a rather bulky 9” x 14” x 23” which could conflict with certain building codes.
Kicking us off is Takagi, a respected name in the business, if a bit less well known than Rheem and Rinnai.
This is a propane unit with a 6.6 GPM flow rating and a respectable 140k maximum BTUh. It operates at a slightly higher than average 82% efficiency for a propane model. Take note that this 6.6 GPM drops to between 2.5 and 3 GPM for colder weather, making it mostly useful for very small homes in colder climates, but good year round in warmer weather.
It’s about the average size for a unit like this, at 6.7” x 13.8” x 20.3”, meaning you can install it pretty much anywhere on the side of your house.
It lacks many of the special features other units have (though can be remote controlled, which is a near necessity with an outdoor unit), but that’s because this is a budget option: It will only set you back around $500, an excellent price for its admirable performance.
Jumping up to a heavier duty option, we have a Rheem. This one is rated for 9.5 GPM at a 35-degree rise…though it should be noted that this drops to 7.4 GPM at only 45 degrees, a rapid drop in heat (likely due to the natural gas power’s lower efficiency rating). As a result, this is not your whole home unit for extreme cold weather as its base GPM might imply.
While it says 9.5 GPM, even for those of us in warmer areas the 7.4 GPM is the more accurate figure, as 95+ degrees is what most of us want from a shower. There, though, it’s still enough to run a sink, shower, dishwasher, and washing machine with a bit of GPM to spare if you want to torque up the heat some more, making it a very solid whole home option for a place with 2-3 people living at once.
Coming in at about $1000 makes it falls right smack on what I’d be willing to pay for a unit with this kind of power, though I’ll reiterate that it becomes much less impressive in cold weather…I’d steer clear unless you live somewhere warm like I do, or just want a good heater for your summer home.
Rinnai rounds out our trifecta of well known, well-respected names in the business. Rinnai, in particular, is known for being high performance (many of their residential units double as commercial/business oriented units), high quality…and high price.
This unit is no exception, hitting 9.4 GPM at a 35-degree rise and 8 GPM at a 50-degree increase. While it also runs on natural gas, it burns much, much hotter than the last two on this list with a max BTUh of 199k. This makes it far more suitable for cold weather options since even at a 100-degree rise you can still get a respectable 4 GPM out of this beast.
It comes with a digital controller and operates at an 83% efficiency. Keep in mind that Rinnai units are generally going to be pretty bulky; this one comes in at 9.3” x 14” x 23”, so it’s going to jut out quite a bit from your wall.
Now the sticking point: The price. While close to $1400 might give some sticker shock, it’s what you can expect from Rinnai units. They eke out as much performance as they can, and charge accordingly.
Let’s come down a little bit and talk about EccoTemp. This company doesn’t get as much spotlight, but in my research, I’ve come to respect them. They offer a lot of very good low-end options. The performance might not be as blazingly high as the Rinnai units, but for someone with small homes or who’s on a budget? They work great.
This particular unit runs on propane and hits a respectable 6.8 GPM at a 35-degree rise, and 5 GPM at a 50-degree rise. It can output a max of 140k BTUh at an 80% efficiency. It takes up a small 15” x 5” x 24” space, making it good for places that need something a bit slimmer.
This makes it surprisingly good for small cold-weather homes, and great for larger warm weather homes and for the roughly $500 price tag, it’s hard to beat that kind of performance. Its main downfall comes with something we haven’t talked about yet (because few units have a significant issue with it): High altitudes. EccoTemp does not recommend using this at altitudes above 3000 feet, so unfortunately if you live in the mountains this unit isn’t for you. It also has a weirdly high minimum BTUh of 25k (the average is 19k) so that’s something to be aware of if you’re energy conscious.
Another low-end option, this time from Rinnai. the first thing you’ve got to know: This is a strictly warm weather option, it has no freeze protection to speak of and lacks the power to properly heat the fluid in colder climates even if it did (clocking in at a lower than average max of 120k BTUh).
What it is made for, however, is mobile homes. Specifically, I mean (though you can use it in a house as well). And for that specific niche, this thing rocks. It has a solid 5.4 GPM (even for a double wide you’re not going to have more than two bathrooms, so little need for more power) and is positively tiny (7.7” x 13.8” x 21”).
Definitely a narrow band option, but in the under $600 range, it’s the best you can really get for the demographic it’s going after.
Noritz has a very simple philosophy with their units: Power.
They don’t have style, they don’t have grace, but what they do have is raw heat for a high volume, and this unit is no exception. Clocking in at 199k BTUh and an immense 11.1 GPM, this is the unit for your heavy-duty needs, either for a very large home or commercial use.
It’s a condensing propane unit, meaning that not only does it output as much heat as any other top of the line model, it does so at a higher efficiency. Even accounting for cold weather, you’re looking at more raw liquid coming through your home scalding hot than anything else on the market.
This is the unit if you want to live in Alaska or something and run two uncomfortably hot showers, a sink, and a dishwasher at the same time just because you can.
The downside to this monstrous power is it also comes with a monstrous size…and a price to match. Weighing in at 9.4” x 18.3” x 24.4” it’s one of the biggest units out there, and the nearly $2000 price tag is what prevents it from being the best unit on this list. In terms of pure performance, it’s definitely the best product, but the price might rightfully make you pause unless you’re worried about extreme cold impacting the quality of your shower.
The iHeat is probably best model on the market…though admittedly that’s partially because it has very little competition.
“Electric” and “Outdoor” are two rare intersections in the market, though this one is a good one for what it is. Outdoor Point of Use models are also fairly rare, so this one makes it on the list for filling a niche that nobody else really thought to fill.
The iHeat is a more specialized unit, acting as a Point of Use intended for outdoor kitchens, parks, yachts, and so on in warm climates. For a Point of Use unit, it has an impressive 3.5 GPM and supports temperatures in a range between 80 and 140 degrees.
Its other main claim to fame is its size: A mere 11.5” x 9” x 4.5”, meaning it can be installed basically anywhere without issue. A niche product for sure, but one I feel serves an important space, and it’s hard to complain with a price of under $300.
The Takagi TK series are mainstays, and it’s easy to see why. They provide a lot of bang for your buck, this one, in particular, having a nice 8 GPM and 190k BTUh in a roughly $1100 package.
It has two main claims to fame in addition to those above average bas statistics.
The first is sophisticated freeze protection, with automatic temperature monitoring and adjustment, so you don’t have to micromanage your product during the winter. Given this is an outdoor unit, this saves you a lot of discomfort in the long term.
The other is it doesn’t require any additional venting, unlike most units (indoor or out). It has its own built-in power venting, meaning installation is, if not precisely easy, very simple and much easier than competitors. This would be the best product on the list if there weren’t one other Takagi even better…
Outdoor Tankless Water Heater Buying guide
Keep in mind that they are a bit more expensive than their tank counterparts, and can be a lot more. The low end we’re looking at here is around $500, with the high end at well over $1000.
This isn’t including expert installation, which I do recommend. While some of the risks of installing a natural gas heater are avoided with an outdoor unit, it’s always best to have somebody who knows what they’re doing fiddle with anything involving plumbing or electricity.
Gallons Per Minute
Abbreviated to GPM, this is how much liquid flow your unit can handle at a given temperature. We’re mostly going to be looking at whole house units today, ones that can serve as your only unit. To that end, some numbers to keep in mind:
-A shower uses between 2 and 2.5 GPM. By regulations in place since the 90’s in the US, 2.5 is maxed for a faucet or sink can output by law.
–A faucet, counterintuitively, usually uses just a bit more GPM than a shower (since it has a more open flow). A bit less for kitchen or bathroom sinks, but more for a tub. Expect between 2.1 and 2.5.
-A dishwasher runs at about 1 GPM, and your washing machine barely hits .25 GPM.
-Most GPM estimates on a unit will be assuming it is raising the fluid temperature somewhere between 30 and 45 degrees, so keep in mind that you’ll have to be more conservative if you live somewhere the groundwater is colder. 5 GPM with a 45-degree rise may be only 2.5 GPM with a 90-degree rise, as an example.
If you crank the heat up to the point a hater can’t handle the flow, you’re going to get cold bursts, and that’s never fun.
British Thermal Units
Knowing the BTUh (the amount of BTUs it outputs per hour) output of your product will let you determine if it gets hot enough to handle your needs if you live somewhere cold.
That means sometimes you might need to do a little quick and dirty math, so here’s your reference:
-1 BTU is enough to raise 1 lb of water 1 degree.
-A single gallon is 8.3 lbs (so 8.3 BTUs = 1 gallon raised 1 degree)
-Groundwater temperature varies by location, the lowest being about 30 degrees in the US.
-To get a comfortable shower, most people prefer it be at least 90 degrees (though that’s a bare minimum; I set mine to 115 degrees). So if you live in a place where it is 30 degrees, you want a unit that can raise that temperature by 60 degrees at least with a decent flow.
There are two main types of tankless heaters: Propane (or natural gas) and Electric.
Both have their pros and cons, but in general Electric units are the most efficient (having a 99% heat transfer efficiency) while natural gas units are less so ( around 80% though condensing units are nearly as efficient as electric).
The main swap comes around when you factor in cold weather; Most Electric units lose 2/3 of their efficiency in cold weather, while propane units stay just as effective in all weathers.
It’s also worth noting that in the short term propane is slightly cheaper than electricity, though the cost of propane is rising faster than the cost of electricity every year.
Looking at the warranty will also reveal how much coverage you get. You may find that your warranty only covers parts one time and that any repairs needed in the future must come out of your pocket. It may cover the cost of any new parts but not include the installation of those parts too.
As with anything, these units take up space. While they take up way less space than tanks, you should always keep in mind two main things:
-The building codes where you live. This particularly applies to apartments and mobile homes, which may have strict practical and legal limits for how big or heavy something you can install can be. You’ll run into it with air conditioning as well.
-Total space available. The measurements I’m giving here are only the measurements of the unit itself, remember that you need proper clearance on all sides (the more the better) to avoid something overheating or catching fire. This applies doubly if you’re putting something in an outdoor shed or storage space; you can’t install the unit too close to the walls or ceiling for safety reasons.
On a lesser note, consider shipping costs where free shipping isn’t available. Even if you’re already buying an $800 unit you may be swayed to a similar unit just because it’s smaller and lighter, and this costs less to ship.