What's your experience with tankless water heaters?

April 3, 2018 11:08 AM

My older house (mid 70s) is in need of a new water heating system. We're looking at either replacing the old hot water tank, or going with a new tankless, hot water on demand system. What have been your experience? Also rent or buy?

The vendor is pushing rentals hard, probably because they make more money that way. Looking at the payments, I'll pay the cost of the unit in rental fees in about 9 years. From my reading tankless heaters last about 16-20 years. Is that a reliable figure? I've had some bad experiences with consumer appliances (washers/dryers) and wonder if tankless is just as prone to failure.

Anyway, appreciate all the feedback.

posted by aeighty to Home & Garden (28 answers total)

We live in Minnesota and have owned a Bosch AquaStar for 16 years. It's great, but make sure you get a good installer. Our Home Depot scheduled installers left us with a few quirks it took a while to sort out. Ours has a user facing temp dial and an internal one and they set the internal one too low to keep up in winter. The other issue is that they lazily tried to reuse as much of the old location and pipes as they could which lead to some drainage issues because the exhaust wasn't adequately sloped.
posted by advicepig at 11:27 AM on April 3, 2018 [2 favorites]

Best answer: I have not bought one. But I have evaluated buying one. They may require a bigger gas line than your existing heater and they almost certainly require more venting (assuming you have gas).

I have a tank water heater buried in the middle of my house that's built out all around it so improving the venting is non-trivial. If yours os located somewhere not-dumb it may not be a big issue. Also consider where the unit will vent as this will drive the condensing vs non-condensing choice.
posted by GuyZero at 11:28 AM on April 3, 2018 [1 favorite]

My condo has a tankless system that is about 10 years old and I've been there for two years with no problems so far. I love it, although it does seem to me that it takes a little longer for the water to heat up. YMMV.
posted by Medieval Maven at 11:30 AM on April 3, 2018

Best answer: We "upgraded" to a tankless water heater at our old house. It takes about 3-5 seconds of the hot water running before the water heater turns on, and another 3-5 seconds for the water (in the pipe) to come up to temperature. What the means is previously, I could be in the kitchen first thing in the morning, turn on the hot water and in 10 seconds I'd have hot water. Then I could turn it off, do something, turn it on and it would be hot, and stay hot.

With the tankless heater, it would take about 15-20 seconds to first get hot water in the kitchen. But if you turned the hot water off and then back on, you'd get 5 seconds of hot water, followed by 5 seconds of cold water, and then a return to hot water. You get that blast of cold water every time you turn off the heater. How many times do you want warm water to wash your hands with in the kitchen? Yay, now you get to waste ten seconds you wouldn't need to or accept that cold grating blast of water that each time makes you hate that tankless heater a little bit more. Think of the "Flames out the side of my head" from Ms. White in Clue ...

For rooms further away from the heater, while it previously took 25 seconds to get hot water in the upstairs bathroom that turned to about 35. So you pretty much just gave up even turning on the hot water if you needed to wash your hands there.

I found the above behaviors the opposite of progress, and hated our tankless heater. I will send all 100 delegates to any meeting to make sure a tankless heater will never again exist in a home I reside in. I have never yet sent 100 delegates to anything before since we started trying the delegate system.

That said, Ms. nobeagle really liked the tankless water heater because she'd never have to worry about running out of hot water for really long showers. Especially as we had 5 people living at home at the time, I'll admit to a few showers that I hastened the end of as I felt the water temp starting to lower.

I'd rather invest in a larger tank.

In the question of renting vs. buying a water heater, unless you're planning to move in the next few years, buy.
posted by nobeagle at 11:33 AM on April 3, 2018 [2 favorites]

We've had one for about 18 months now and are pretty happy with it. On the plus side, once it kicks in you get unlimited hot water for as many showers, etc., as you need, and if you get a high enough flow model, you can have multiple showers at once, shower plus dishwasher, whatever. On the minus side, ours takes a long time to get going - maybe a minute - so I feel like we're always wasting water. If you get one, I would ask about options for recirculation (supposedly helps with the startup time) and also potentially a "starter button" in the bathroom that you can manually press before you turn the water on? I actually learned about that possibility from another AskMe post, I have no idea how well it works.

In theory it saves on energy costs, but I'm not sure that's been the case for us. Ours is a gas-heated model, and we are a household of 2 who only runs the dishwasher and laundry once a week, so maybe it's just a really small part of our gas usage, I don't know. Consumption certainly hasn't increased, though.

As for buy vs. rent, I see no reason at all to rent an appliance. I can't tell you exactly how long they last, but they have almost no moving parts, so there's really no reason they should die at anything like the rate of a washing machine.
posted by Joey Buttafoucault at 11:35 AM on April 3, 2018 [1 favorite]

I had one, though in Australia, not sure if US climate would effect them or how they work. I loved it & miss it terribly. I preferred how the water felt, I loved that it didn't rust out & explode at any point like my tank, I loved that I didn't have to replace it and strangely i thought the water just felt better. Also I never ran out of hot water, no matter how many people came to visit.
posted by wwax at 11:41 AM on April 3, 2018

I installed tankless in my previous house and now in my current house. After having a tank heater explode and flood my house, I will never go back to tank. Yes, it's a little annoying to have to wait for the hot water to get to the faucet but it never runs out and it is way more efficient with gas usage.
posted by joan_holloway at 11:44 AM on April 3, 2018 [1 favorite]

Best answer: As a few have mentioned, depending on where they are in the house, there can be a lag between the hot water heating...but depending on how your house is currently set up, the lag might be the same. Our conventional HWH is on the opposite end of the house from our kitchen, and it took for fucking ever for water to heat up in that sink. I've installed and used sink-specific heaters (tankless faucet heater? I don't know the right nomenclature) and they work GREAT, so if you do have this problem, they can help and they're pretty cheap.

This might not be a concern of yours, but we live in a pretty small house, and want to eventually go tankless because that's a solid 6 square feet of space we're missing out on, and our HWH is in a pretty inconvenient spot. Clearly YMMV on this.
posted by furnace.heart at 11:50 AM on April 3, 2018 [1 favorite]

We had an old one (it was in place when we moved in in 01) which we replaced I think around 2013. New one (Vaillant) has been working well since then with minimal maintenance. The new one in particular heats up very quickly - in the kitchen (near the boiler) it's pretty much instant. Having grown up with tank systems I much prefer the tankless boilers. Definitely buy rather than rent.
posted by crocomancer at 11:53 AM on April 3, 2018

Best answer: All the modern tankless heaters require electricity, even if they use gas to heat, so without backup power, you won't have any hot water in a power outage.

The better modern tank-type water heaters are pretty well insulated in my experience.

Rental seems like a bad deal. Possibly if it means included coverage beyond the warranty that would come with a purchase, but (in aggregate) they only offer this because somebody's making a profit with the scheme.
posted by mmagin at 12:02 PM on April 3, 2018

We like ours. Pro: the biggest pro is that we never run out of hot water, even when we have multiple guests. If that's a problem for you with a tank style heater, and you can deal with the venting requirements, tankless could work well for you. Also pro: ours is not really any slower to reach "hot" than the tank was. Con: it hasn't been any cheaper to operate than the tank was (our summer gas bill, with only cooking and hot water, has been consistent since we bought the house). Another con: they had to cut a lot of holes in the ceiling of our basement to run the higher capacity gas line it needed.

Ours could be installed directly on an exterior wall, so aside from the heart flutter watching them cut a big hole in the house we didn't have any venting issues. As GuyZero said, if you need it to be installed in a completely interior room, the venting requirement may make that impossible.
posted by fedward at 12:04 PM on April 3, 2018

Best answer: I don't have a tankless water heater, though my husband is a plumber. He doesn't want to install a tankless system in our house because of the slow-to-heat problem, and because they require yearly maintenance. We're on the verge of getting a new water heater ourselves and will be putting a tank. Another plumber friend uses their tankless water heater for their hydronic radiant heating system and loves it for that purpose, but they also have problems with the slow-to-heat issue for washing and cooking.
posted by little king trashmouth at 12:10 PM on April 3, 2018 [3 favorites]

I have a Navien combination boiler (both baseboard heating and hot water), now about eight years old. The only con has been that it takes a while for the hot water to reach the upstairs. Otherwise, endless hot water + can do laundry and/or the dishes at the same time as taking a shower = yay.
posted by thomas j wise at 12:31 PM on April 3, 2018

Please double check this but when I looked into them a few years ago I was under the impression that they were both more expensive than tank heaters, while having a shorter warranty. That was just a cursory search though.
posted by vignettist at 12:50 PM on April 3, 2018

Best answer: Our water heater died recently, and we did some research on tankless vs tank. I wasn't completely sold on the benefits of the tankless when you considered the cost and the extra maintenance, but we asked about it when our very highly trusted contractors came out. They basically said that someday the tankless heaters will be awesome, but it's still early and technology isn't really there yet. He's had to come back and replace half the ones he's installed with traditional tank heaters, and said he's talked to many other business in the area who have done the same. We went with a larger tank and it's been great.
posted by thejanna at 12:53 PM on April 3, 2018 [2 favorites]

Best answer: We installed a tankless water heater (a Takagi T-KJr) into an older house about 11 years ago and really like it. It is more energy efficient than the one it replaced. Yes, there is a lag to get hot water to the farthest taps, but it doesn't bother me; I just wash my hands in cold water. We have very hard water that is apparently bad for them; I hate water softeners so we've made do with a whole-house filter. It stopped working last year, and there are no repair technicians anywhere nearby (Midwest US). My partner called the company and they led him through the repair process and now it works like new again...for free. One other potential issue - our older model HE clothes washer doesn't pull enough hot water (it takes short draws, stopping after a few seconds) to really get the water hot. I wash laundry primarily in cold water anyway, so this hasn't ever bothered me. I'm giving you the potential downsides, but for us they aren't dealbreakers and I would definitely install one again.
posted by Empidonax at 12:56 PM on April 3, 2018 [2 favorites]

We have a tankless water heater on ONE sink in the house, the kitchen sink. It was about 8-9 years old when it died. In our research in replacing it, we realized that we had had a model which was WAY to powerful for one sink. Oh, the money we lost operating that thing for 8 years! We now have one that is sized for the job it is doing and our electricity bill amount has had a significant drop. So, my advice is, make sure you don't get one that is too big for the size of the job it will be doing, it's not cheap to operate. Also, don't expect it to be instantly hot, there is a time lag, as others are reporting. (In our case, we got one in the kitchen sink because our tank hot water heater was on the other side of the house, and it took ages to get hot water in the kitchen sink. The tankless gets us hot water sooner than that, because it's directly under the sink in the basement.)
posted by molasses at 1:33 PM on April 3, 2018

We have a tankless system and it works pretty well. Our unit is also a long way away from the bathroom we use the most often, so far off that it would take a minute or two to get hot water once we turned on the taps. We solved this by putting in an under-sink recirculating pump. You push a button and it pumps water from the hot pipe to the cold pipe, stopping when the water in the hot pipe is hot. At that point you can turn on the shower and be happy. The whole process takes a couple of minutes in our house, which is tolerable.
posted by It's Never Lurgi at 2:43 PM on April 3, 2018

"How many times do you want warm water to wash your hands with in the kitchen? Yay, now you get to waste ten seconds you wouldn't need to or accept that cold grating blast of water that each time makes you hate that tankless heater a little bit more."

What? I mean, at home I wash my hands with whatever water temperature comes out from the direction I randomly pushed the thing on. Never considered hot water to be a necessity for washing hands, certainly not if it's going to take 10 seconds of water watching to get to that point. Hot water is good for dishes and showers, but the water will be running anyway. You just make it sound as though room and cold temp water are some kind of acid that hands dare not touch.
posted by GoblinHoney at 2:55 PM on April 3, 2018 [1 favorite]

LOOOOOOOOOOOOOOOOOOOOOOOOOOOOVE IT.
posted by SinAesthetic at 3:42 PM on April 3, 2018

Best answer: This is a vanishingly unlikely series of events; nevertheless this all happened to a (real-life) friend of mine.

My friend, I'll call him Bill because that's his name, was in the middle of retiring from CT to NC and had homes in both places. He was in NC three winters ago while CT experienced a cold snap, which caused a pipe to burst. The burst pipe was downstream of his tankless water heater, which interpreted the leak as demand and filled the house with hot water until the propane tank ran out. That's when the heat shut off and all the pipes in the house froze ("even the little tiny ones under the sinks!"), filling the house with ice.

Then it all thawed.

His neighbors noticed water running out from under all the doors and called him in NC. The house probably should have been demolished, but instead he gutted it to the studs and rebuilt it.

That all said, I have a Takagi propane tankless heater in my house. It works fine, though it takes a while for hot water to get to the master bathroom (the farthest point under the same roof.) I reckon the same would be true of a traditional water heater.
posted by workerant at 3:46 PM on April 3, 2018 [1 favorite]

Best answer: If 'tankless' is the same thing as a boiler in Europe (cursory image searches seeming to indicate as much), in my experience of having used both the latter is far superior. The hot water doesn't 'run out' as it's heated on-demand, and switches from hot to cold much more quickly, resulting in much less water waste.
posted by myotahapea at 3:51 PM on April 3, 2018

We got a tankless heater 6-7 years ago and are happy with it. At the time we didn't think we'd be living in the house for that much longer so got a rental. Next time I will purchase the unit outright.
posted by any portmanteau in a storm at 4:23 PM on April 3, 2018

What furnace heart said. There exist tankless electric water heaters for individual points of use if it's that much of an issue. If you like to just have a trickle of warm water, though, you'll probably want to go with the style that has a small tank on it since all tankless heaters require a minimum flow rate to kick on, lest they overheat.

Either way you'll save energy relative to keeping 40+ gallons of water hot 24x7. Don't think I'd rent one though
posted by wierdo at 3:15 AM on April 4, 2018

Best answer: We replaced our tankless heater with a stainless-steel tank because the water where we live is heavily mineralized, and the mineral deposits that were building up inside the heating coil gradually reduced our hot water output to a lukewarm trickle.
posted by brianogilvie at 2:34 PM on April 4, 2018 [1 favorite]

We built our house in 2002 and installed two tankless propane water heaters: a Takagi TK-1 in the side of the house where the laundry, big showers and bathtub are; and a smaller one (Bosch Aquastar) with a standing pilot for kitchen use. They have been brilliant. The standing pilot is in case of power cuts, when we rig a temporary shower to the kitchen tap and enjoy hot showers plus hot water for washing dishes and the like.

They have required a little maintenance, about every five years. DIY is pretty easy with them. I have never needed a service call - 16 years of no-hassle water heating and if I want it a half-hour shower is right there.
posted by jet_silver at 8:21 PM on April 4, 2018

Lots of solid advice here. When I built my home I went with a hybrid heat-pump tank water heater. The modern standards make these very energy efficient. I personally wanted a home that was completely electric b/c I think modern sustainability means fully electrifying all parts of the modern economy. Also, when I read about tankless heaters, I was told that the electric tankless heaters were not very efficient.

But again, I believe that hybrid heat pump water heaters may be the most efficient and have lots of benefits, and I believe government efficiency standards are pushing almost all tank water heaters to this format.
posted by bove at 12:42 PM on April 5, 2018

I installed an ELECTRIC tankless water heater in our 1 bathroom house. It works amazing. Instant and endless hot water to the shower and kitchen. It did require we have 200 Amp service, which we were lucky to already have. I also had to have an electrician do the wiring, and it took up a 3 20 amp breakers in our breaker box.

It also is only as big as about 2-3 phone books? So the closet space was reclaimed as extra storage. Of course the shorter the water lines and proximity to sinks makes a difference. Our kitchen sink is about 25 feet under the house from the heater and it still only takes about 10-15 seconds to heat up. This is also with PEX water lines, as opposed to copper or galvanized, so it is able to warm up quickly.
posted by Sprocket at 8:51 PM on April 5, 2018