Reuben's Home Inspection Blog


Tankless Water Heaters Revisited

In last week's blog post, I discussed the amount of money I might save by having a tankless water heater installed, and I concluded that I would never see a return on my investment.  I received a lot of good feedback from that post, both for and against tankless water heaters.  I thought it would be worth bringing up a few few of these points in another post.


  • You can't put a price tag on going green.  There's no dispute about this - tankless water heaters use less energy.  Doing the environmentally responsible thing doesn't always have a measurable return on investment.  I mentioned this last week, but only briefly.   Not everything we spend money on will give us a return on our investment - we all know that.   After all, what's the payback period on a sofa?
  • Tankless water heaters make sense for a cabin / vacation home.  Traditional water heaters have a 'vacation' setting, but I've heard it's a bad idea to use this setting, because it greatly increases the potential for legionella pneumophila growth.   Having a tankless water heater installed in one of these settings would result in much more than a 25% fuel savings.
  • Energy Star Tax Credit.  This $300 tax credit which includes tankless water heaters, expires December 31, 2011.   You can read about it here - tax credit.  I'm guessing we'll see another one show up when this one ends.
  • Fuel costs will continue to rise.  As we all know, fuel costs continually increase.  If fuel costs tripled in the next 20 years at a linear rate, a tankless water heater would actually give me a return on my investment, using the numbers from the example last week.


  • Low water flow = no hot water.  If there isn't enough hot water flow, a tankless water heater just won't turn on.  One person even commented that they had to turn on the hot water faucet at their bathroom sink and leave it on the entire time they took a shower, or they couldn't get hot water.  For instance, Rinnai tankless water heaters need at least .6 gallons per minute, Bosch units need .65 gallons per minute, and Rheem at least .4 gallons per minute of hot water flow to kick on.
  • The cold water sandwich.  If you think gefilte fish sandwiches sound bad, just try one of these.  The cold water sandwich effect is something that happens with every tankless water heater.  When the faucet is turned on, off, and on again, you'll end up with a slug of cold water interrupting your hot water flow.  Some tankless water heaters require the call for hot water to last for at least three seconds before the burners turn on, so there can be several layers of hot and cold water in the pipes.  This doesn't exist with traditional water heaters.  You can read more about this at Rinnai's web site - they claim to have nearly eliminated the cold water sandwich, but not completely.
  • The long wait for hot water.  I already have to wait for approximately forever to get hot water at my kitchen sink, but the wait would be even longer with a tankless water heater.  One interesting solution that I heard a plumber mention was to install a dedicated 3/8" supply line to his kitchen sink from the water heater.   He claimed that this still provided just as much water flow, and made the wait much shorter.  I've considered doing this at my own house, although this is technically a code violation.

For me, a tankless water heater doesn't make sense just yet.  I'm waiting for the price gap between tankless water heaters and standard water heaters to get a little smaller.  I have the temperature cranked up on my water heater with a tempering valve installed, so I never run out of hot water.  Maybe by the time my kids are teenagers I'll have a different opinion of tankless water heaters.

Reuben Saltzman, Structure Tech Home Inspections


Comment balloon 14 commentsReuben Saltzman • October 25 2011 05:56AM


Hi Rebuen, I am not sure if I mentioned we had trouble with our tankless...we had a drilled well and it kept picking up small particles and clogging the heater....we ended up having the pump pulled up in the well, they said it was too close to the bottom, still had the problem. 

Posted by Brin Realty Associates Team At Bean Group, Amherst NH homes and Southern NH real estate (Bean Group | Brin Realty Associates) over 7 years ago

Hi Rene - I understand tankless water heaters have inlet screens that are supposed to be cleaned every month; was your issue related to this?

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 7 years ago

Hi Rueben,

As the debate continues, client's often ask "why not a tankless water heater"?

I tell them they can get one installed but they would be disappointed with the results. Some did and were.

For the costs of the unit plus installation, I can't justify it as a good return on your investment.

Have a good day, Clint McKie

Posted by Clint Mckie, Desert Sun Home, Comm. Inspection 1-575-706-5586 (Desert Sun Home, commercial Inspections) over 7 years ago

Reuben - I am not in the market currently, but am getting more educated on the topic; I was not aware tankless water heaters had as many issues as they do.

Posted by Carol Zingone, Global Realtor in Jax Beach, FL - ABR, CRS, CIPS (Berkshire Hathaway Home Services Florida Network Realty) over 7 years ago

Reuben-Your last post on this I thought laid it out well, I'm still not convinced that they're worth the money.

Posted by Michael S. Bolton, MN Appraiser (Michael S. Bolton,Inc.) over 7 years ago

Wow! Just when I was about to make a purchase. The cons are really bad. I had not heard that it took longer to get hot water to you. Now I really have something to think about. I guess I will call a plumber!!

Posted by Diane Grady (Endless Summer Realty) over 7 years ago

Clint - me neither.

Carol - the reviews are divided; people seem to either love 'em or hate 'em.

Michael - thanks - I agree.

Diane - sorry to talk you out of buying one, but on the other hand, at least you know more about them. 

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 7 years ago

Reuben....I am curious about the Con of not having enough hot water. In my house with three teenage girls and having a hot water tank, we seem to run out of hot water, waiting for the tank to refill or heat back up.  But my mother, who lives at the beach, has a tankless.  I think one of the main reasons when she renovated was to save on space in her small home.  Now, when we are all there in the summer, everyone taking showers after a day at the beach (and not just my family but often my siblings and their families too) we NEVER run out of hot water.  And there is never a wait for it to get hot.  And the pressure is great.  So I have always thought they were great.  So, what am I missing?

Posted by Christine Smith, Exclusive Buyer Agent & Attorney, Canton, MA (Buyers Brokers Only LLC - over 7 years ago


Thanks for the update. And, yes there are a few more issues than you raised last week. So, it's up to the consumer to decide, which one of the points is significant to them.



Posted by Brian Madigan, LL.B., Broker (RE/MAX West Realty Inc., Brokerage (Toronto)) over 7 years ago

Christine - what you're mentioning is definitely one of the pros of tankless water heaters; you have an endless supply of hot water.  When the ground water is fairly warm, you can also get a fair amount of it at once.  As for the wait, it varies with different installations, but this is a known issue for tankless water heaters.  I'm glad it's working out well at your mothers!

Brian - exactly.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 7 years ago

I'm looking forward to seeing how my indirect unit operates. It is supposed to loose less than 1 degree per hour. Should be pretty efficient with a 96% AFUE boiler. 

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) over 7 years ago

Until you mentioned it on my post, I had never heard of the "cold-water sandwich!"

And now, once again, I had never heard of the "gefilte-fish sandwich."  I've seen those little planks in their jars and they look nasty.  Now you have made me think how they would be with some lettuce, tomato and mayo!

My 75-gal gas tank costs me $15/month.  If I saved even 50% on a new tank, any new tank, I am going to bet the earth won't notice.  It will notice the next volcano though!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

James - 1 degree per hour is insane.  I wonder why standard water heaters don't have super-insulated tanks like that?  I'm also curious - why is the tank warranty only 10 years?  

Jay - Ok, you got me.  I've never heard of a gefilte-fish sandwich either.  I invented it... but I haven't tried it yet.  I have a seven-year-old jar of gefilte fish sitting on my shelf, and I haven't touched it yet.  Maybe I'll pass it down to my children.

As for your $15/month gas bill - that sounds about right.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 7 years ago

Reuben I grew up with tankless hot water heaters in Europe in the late 1970's, they work perfectly fine. We also rent a vacation home that sleeps 8 and never had a problem with the tankless hotwater tank that was there. Why pay for hot water when the vacation home is empty. Thanks for the blog, always good to hear the pros & cons.

Posted by David Popoff, Realtor®,SRS, Green ~ Fairfield County, Ct (DMK Real Estate ) over 7 years ago