On demand hot water heater, the good, the bad and th- WHY IS THE WATER COLD!?

Jun 26 2017
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Now that its been a couple of years of living with an on demand hot water heater (also called a tankless hot water heater), I wanted to put in my two cents. When I renovated the house I really didn’t want anything to do with a regular hot water heater. A: they take up a ton of room and B: They run out! Seriously, it just seemed to me that common sense would say that heating the water ONLY when you need it would be a lot more economic then paying to keep a huge amount of water hot all of the time. Renovating the bathroom takes a lot of work and there are so many things that you can do to ensure that you keep the bathroom as the place that you want to be. From using the floors to walls guide for wet walls to stop the walls from becoming moldy, to ensuring that you have the right water temperature and pressure, you have a lot to consider. The fact you have the right heater is important, too. So, how’s that been working out for us? Well, there’s a lot that goes into that answer!

Living with a whole house on demand hot water heater, how much it costs to run, how easy it is to install and what its like to live with, with well water.

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First, I want to say that I have no regrets. I was the one that installed my on demand hot water heater and it wasn’t at all hard to do. If, for instance, your big old tank hot water heater dies suddenly and you decide to replace it with an on demand instead, you could literally get it done (by yourself) in a weekend with a little bit of basic electrical and plumbing knowledge. This is not a tutorial on how to install one of these bad boys but I will say that they take a TON of electrical power. You will wonder, as you’re installing it if you are, in fact, installing a bomb in your basement. Nothing else electrical in your home will come close to the ampage these things need to run. I spent over $600 on the enormous electrical wires alone and the huge breakers to run this thing and, during all of that and because of it, I did wonder if it was going to cost a fortune every time I wanted hot water.


Living with a whole house on demand hot water heater, how much it costs to run, how easy it is to install and what its like to live with, with well water.

My electrical bill is half of the national average right now and rarely gets much above $100 per month so, all in, I believe it was the right choice from a cost perspective. I would say I run hot water every day here, whether it is just washing my hands, taking a shower or bath, or using my dishwasher. I do have to mention though my on demand hot water heater cost us $800 brand new from Menards. So, all in, do I think I’m saving money compared to a tank hot water heater? A little, but I DO NOT believe it would be worth replacing a perfectly functioning tank hot water heater. (In other words: Don’t replace your tank with one of these until you need to.)

So, how does it work?

At my kitchen sink, my shower and sink on the main floor and my sinks/bathroom down in the basement, I have no problems and get hot water there without delay and without incident. (my water heater is directly beneath my kitchen in the basement.) However, if I mix the hot water (at any time at any of these locations) with more then a little cold water I run the risk of the hot water heater cutting off completely. Here’s the thing with these on demand water heaters: If you don’t run enough water through them they’ll either cut off or not kick on at ALL. I have a well here and a pressure tank so my water pressure isn’t even comparable to say the water pressure most people get in town on city water.

Living with a whole house on demand hot water heater, how much it costs to run, how easy it is to install and what its like to live with, with well water.

When I first took a shower in my master bathroom the water NEVER got hot. I tried the sink up there (on the second floor) and the water NEVER got hot. If I ran them both at the same time – then I would get hot water! In the end, every time I wanted hot water at my sink or in my shower, I had to run my tub faucet at a trickle to keep enough water running through the on demand hot water heater so it would keep heating the water. I lived with this for quite awhile until I couldn’t stand it anymore and unscrewed the filter from the sink faucet and: problem solved. Now I just have to be careful because every time I turn on my sink I get a torrential flood. The shower I took care of by replacing the shower head (I happened to have an extra one) and that immediately fixed my problem of hot water in my master bathroom. However, I have hard water (and no water softener) so, over time, the shower head will slowly get gummed up with calcium and needs to be taken off and thoroughly cleaned or it won’t let enough water through it to give me hot water to shower with and then I’m back to running the tub faucet when I shower. *sighs*

Living with a whole house on demand hot water heater, how much it costs to run, how easy it is to install and what its like to live with, with well water.

In the end, I can live with all of that because seriously, shower heads really should be cleaned every couple of months anyway. The big problem was that I couldn’t mix cold water EVER (not even a little bit!) or the on demand hot water heater would stop heating water in my master bathroom. So, after much adjusting, I found the perfect temperature. (Note here: by the time the water gets up to my second floor it is cooler then say, at my kitchen sink, so the water is still hot enough there that I feel comfortable washing dishes by hand.)

Living with a whole house on demand hot water heater, how much it costs to run, how easy it is to install and what its like to live with, with well water.

None of this would be a problem if A: you live in town and have great water pressure and/or B: You have a water softener. Our special little mix of low pressure well water and no water softener is causing us these annoying issues that most folks just wouldn’t have. Do I regret our on demand hot water heater now that I’m living with these issues? No, because in the end, it is not that big of a deal. However, I did get a real laugh when I did a google search for on demand hot water heater problems and the first one that came up was, “Shower not getting hot water.” So, I’m not the only one that ran into this situation and I have to believe that any “low flow” shower heads or faucets would literally never get hot water – so that’s something you have to keep in mind if you consider going on demand.

Living with a whole house on demand hot water heater, how much it costs to run, how easy it is to install and what its like to live with, with well water.

Now I purchased the biggest on demand hot water heater that they make so it would take care of my whole house and if I could go back I think I would have installed a small on demand hot water heater on every floor instead. It would have cost more (so much more electrical wire to run…) but smaller on demand water heaters require less water run through them to kick on. So then I wouldn’t have ANY of these issues at all and if you look at the manufacturer websites for these things, that really is what they recommend. So, if you’re considering going on demand I would recommend you purchase a small one for every floor or one for each kitchen and bath.

Hope that helps if you’re considering making the switch!

Living with a whole house on demand hot water heater, how much it costs to run, how easy it is to install and what its like to live with, with well water.


  1. Jenny Young
    June 27, 2017 at 3:49 am

    By ‘on demand’ do you mean the same thing as a tankless hot water heater? We’re considering switching to a tankless heater at our house. We use well water, have not water softener & have low water pressure. After reading this I’m wondering if we should reconsider.

    • June 27, 2017 at 3:13 pm

      Hi Jenny! Yup it is the same thing as a Tankless Hot Water Heater 🙂 Well, you might really benefit from just calling the manufacturer and letting them know your situation (which sounds exactly like ours!) they probably will have some pretty good advice. I think if we had two small tankless water heaters we would be a LOT better off!

  2. June 27, 2017 at 11:48 am

    Oh my gosh…..So glad you wrote this post. My husband has been wanting to make the switch for a long time now. We don’t know anyone who has one so of course we were only hearing the good. This gives us some pros and cons to discuss before actually going through with it. I really like your site!

    • June 27, 2017 at 3:14 pm

      Hey Kathleen! That’s exactly why I wrote this post because I couldn’t find any actual real world experience using them when I decided to take the plunge for us. I think it does save us money compared to a tank water heater but there are definitely some cons we’re dealing with… lol

  3. June 27, 2017 at 8:11 pm

    Thank you so much for sharing this. I’ve been looking into a tankless water heater for a few years because they seem so much more efficient. I’m really glad to know about the water pressure issue because we live in California and have lo-flow everything.

    • June 28, 2017 at 1:09 pm

      Hey Rebecca, your low flo situation is definitely something to keep in mind if you decide to go tankless. Regardless of our issues though I would still recommend them, thanks for coming by!

  4. June 28, 2017 at 1:02 am

    We are about to start renovating our RV and we are talking about putting one in. Our goal is all electric in our RV and my brother in law put a tankless hot water heater in his.

    • June 28, 2017 at 1:12 pm

      Oh Sheena, a little tankless water heater would be perfect in that situation!

  5. Lace Faerie
    June 28, 2017 at 6:59 am

    We have a tankless hot water heater and we have had the same problems. We have a 1000 sq ft ranch house and it takes so long to get the hot water to the bathroom sink in the middle of the house, I rarely use the hot water for a quick wash of my hands. Or, I start the water running before using the toilet to ensure a warm wash. I also hate that I have to keep the water running with force to keep the water hot when working in the sink. It feels very wasteful of water. That being said, having three teens and always being the one the hot water ran out on, I love the endless hot water. And that’s how I put it to people who ask me how I like the tankless. I tell them it’s endless hot water, not instant hot water.

    • June 28, 2017 at 1:14 pm

      Hey Lace, you summed it up perfectly! Despite the issue and, I totally agree, wasting water waiting for the hot water! I would still recommend them because the hot water is truly endless!

  6. June 28, 2017 at 7:28 am

    These are very common in the UK, we call the combi boilers as they do the combination of the central heating and the hot water generally.
    We had one in our first 2 houses but now we have a water tank. Water pressure is your main problem isn’t it, get that right and they work great.
    In both cases our boiler was up in the bathroom upstairs and that did mean we rarely had a problem with the taps not being open enough so luckily we were able to mix hot and cold (my husband likes his showers WAY hotter than I do) . Although in house 2 we did get a some sort of pump to help with waterpressure for the shower, I don’t know if you can get the same where you are.
    .I would think of them as best for smaller houses, definitely a money saver for small households. Once you have a bunch of teenagers showering every 5 minutes they become less economic. At least that’s what we have found.
    Not sure how helpful that is, I think this is a valuable discussion to be having, especially reading the other comments. Seems people are not sure whether to switch or not.

    • June 28, 2017 at 1:25 pm

      Julie, thank you for sharing your experience! I agree they are definitely more economical for smaller households though one gal mentioned that living with three teenagers she loved hers because the hot water never runs out! I don’t think they’ve “perfected” them yet but I do think they’re on the the right track and, despite out own cons, I would still recommend them. Thanks for reading and coming by!

  7. June 28, 2017 at 1:33 pm

    This is really useful information. I will consider your experiences before purchasing an on-demand heater.

    • June 28, 2017 at 2:01 pm

      Glad I could help Barbara, thanks for coming by!

  8. Jann Olson
    June 29, 2017 at 4:57 am

    Not sure what we have, but always have hot water. Cold showers are no fun!! Thanks for sharing with SYC.

  9. June 29, 2017 at 8:21 pm

    Thanks for your honest assessment. We just replaced our dishwasher and garbage disposal, and our plumber recommended against the instant on water heater we were thinking of installing. He said he replaces them about every 2 years when people have them. Also, we have a tankless water heater so our tank is already energy efficient and supplies all the hot water we need.

    • June 29, 2017 at 8:40 pm

      Hi there, thanks for coming and reading! I’m kind of confused, as far as I knew a tankless hot water heater and an on demand hot water heater are the same thing?

  10. June 30, 2017 at 4:17 pm

    Thanks for sharing this. We’ve been talking about getting one for a while so I found this very interesting. I’ve pinned it to share with my husband.

    • June 30, 2017 at 4:20 pm

      Thanks for coming by and reading Donna!

  11. July 1, 2017 at 4:02 pm

    Interesting. I didn’t know anything about these. Thank you.

  12. July 3, 2017 at 11:08 pm

    Oh wow, I didn’t know anything about these water heaters. Thanks for sharing at the #InspirationSpotlight party @DearCreatives have a great 4th of July.

    • July 5, 2017 at 2:47 pm

      Thanks for coming by Theresa, hope you had a great holiday!

  13. Nancy J Mock
    July 5, 2017 at 7:14 pm

    Thanks for all the hints! I am having an on-demand hot water installed in my small cottage (14×24), but only running hot water to shower and kitchen sink (living in Florida, it is not needed elsewhere). Your hints may well keep my frustration level under control! Thanks!

    • July 5, 2017 at 7:58 pm

      Thanks for coming by and reading Nancy, hopefully some of my tips and tricks will help you along the way! I just cleaned my shower head and to do so I just took it off and soaked it in vinegar for an hour and bam, like brand new!

  14. Danelle
    July 6, 2017 at 6:31 pm

    We also use a tankless hot water system. Ours is propane, since we live off-grid. We had to adjust the water pressure knob on the water heater to stop the problem with cold showers. It still gets wonky if I use the button on the shower knob to turn off the spray (like when shampooing the dogs) but overall that solved our problem. I agree though, that smaller units in each room with water needs is the way to go in the future. One issue we have though, is in summer, here in Sunny South Carolina, the cold water is hot at first, (the lines are shallow here) so it can be sneaky to think we have the water adjusted then the real cold water comes through!!

    • July 6, 2017 at 8:25 pm

      Danielle, thank you for sharing your story with us! lol it sounds like you know exactly the cons with going tankless right now, I’m glad we’re not the only ones! We just got our shower head clean so (hopefully) we won’t have cold showers for a couple of months!

  15. Gardenpat
    September 24, 2017 at 8:37 pm

    We replaced our 3 conventional hot water heaters with a single tankless hot water heater 5 years ago. It runs in natural gas rather than electricity.

    It is located in the basement of our 3 story Victorian home built in 1890. I wondered if it would really be able to handle 4 bathrooms, clothes washer and kitchen sink and dishwasher! It takes about a minute to water heated up to the third floor bathroom but a minute is not long to wait!!! Our gas bill has gone down appreciably and so has our electric bill since 2 of our 3 previous water heaters were electric and only the third one was gas!

    We are over the moon pleased with the result and have saved tons of $$ with this!!

    • September 25, 2017 at 3:36 pm

      Thank you so much for coming by and sharing your experience! YES, I think they definitely save us money and we’ve been really happy with ours too!

  16. November 20, 2017 at 6:52 pm

    Tarahlynn thanks for the awesome presentation. I will consider your experiences before purchasing an on-demand heater.

  17. January 31, 2018 at 3:12 am

    I just had to read portions of this out loud to Hubby as his father has a one of these in the house where we stay up north and it NEVER HAS HOT WATER IN THE SHOWER unless you run the water in sink at the same time. I can’t believe it’s not just us!! I’d love for you to share over at a new party called Let’s Party https://themarkandjanshow.com/2018/01/02/lets-party-6/ … we look forward to seeing you there!

    • January 31, 2018 at 4:05 pm

      Hey Jan! Yeah I’m a little put off by the whole thing lol I think its saving me a lot of money though! I need to clean my shower head out because that helps a ton. I think, in the end, my only real way to “fix” it would be to install a bigger pressure tank in my basement. Thanks for coming by Jan!

  18. February 11, 2018 at 2:43 pm

    Tarahlynn, thanks for presenting “the other side” – you’ve given me a lot to think about. Hope I can come to a decision before old standard water heater goes out!

    • February 11, 2018 at 9:25 pm

      Hi Jean, thanks for coming by and reading!

  19. February 13, 2018 at 7:59 pm

    Hi Tara. What an interesting story. Who new water heaters can be so fussy? I appreciate the advice of getting multiple small water heaters and having one for every floor. Anyway, it must be so cool to live in your Grandma’s house. I bet it’s like living in a memory wonderland. I wish my grandmother’s house was available for purchase.

    • February 13, 2018 at 8:10 pm

      Hi Joy, it is a wonderful home to live in because it felt like home my whole life! I’m planning on (hopefully) upgrading my pressure tank and that will increase my water pressure throughout my whole house and I think that will help a lot!

  20. March 29, 2018 at 10:15 pm

    Oh wow, I didn’t know anything about these water heaters. Thanks for sharing this, it really helped us a lot. Keep on posting useful blogs!

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