Electric Tankless and Another Funny Video

Wow! It’s been a long time since my last post.  I got really behind during the Christmas holidays and then we had a family tragedy.  Anyway, I apologize for the long delay.

This is a pretty long post so I have another funny cartoon at the end.  Think of it as desert.  I think you’ll like it, my kids did and they are cartoon connoisseurs.  But first some actual plumbing info.

I have recently been doing some pretty intense research into Electric Tankless Water Heaters for a customer.  I did a 3 part series about Tankless in general a while back (check under Green Plumbing Design) but I didn’t talk much about Electric tankless ecxept to say that they don’t make much sense.

Well, at the risk of making all the Electric tankless manufacturers mad, what I found out in my research just confirmed that they really don’t make much sense.  I just have more information as to why not now.  Since tankless water heaters are being marketed so heavily right now, I wanted to give you the bottom line on what the marketing may not tell you.  Then at least you will be able to make an informed decision if you are considering tankless.

First of all, in case you missed the earlier posts, it is important to understand the basic operation of a tankless water heater.  All tankless heaters, whether electric or gas, use the same basic process to heat water.
1)When a hot water faucet is opened this causes water to flow through the tankless unit.
2) When the volume of flow is enough to trigger the unit to come on it begins heating water.
3)The amount of water that the heater allows to flow through is regulated by the desired outlet temperature.
4)This is, in turn, affected by the temperature of the incoming water.  The colder the incoming water the more heat the heater has to create.

That’s why the performance of tankless water heaters is measured by how many gallons per minute (GPM) the heater will deliver at a desired Temperature Rise.  The greater the desired Temperature Rise, the less Gallons per Minute of hot water can be produced.

How many GPM a tankless heater can deliver is entirely dependent on how much energy (either electric or gas) the unit has available to heat the water.  If you want more hot water you have to use more energy.  In a gas tankless this means more BTUs.  In an electric tankless this means more kilowatts, which also means a bigger amperage draw.  There is no way to get around this, it’s just the way it is.

Since we are talking  about electric tankless, the only thing I will say about gas models is that they almost always have better performance than electric models.  The “largest” electric tankless heaters can’t match the output of a “standard” gas tankless unit.  For the record, “regular”, tank type water heaters have the same differences.  Gas units just heat water faster than electric, tankless or otherwise.

Now that you know the basic concepts, here’s why I don’t think an electric tankless is a good idea:

The largest unit I could find is only capable of delivering around 5 GPM (gallons per minute) at a modest 50° temperature rise.  At a 60° rise this drops to 4.3 GPM.  By the way, the only people I know who recommend using a 50° temperature rise when sizing a heater are the tankless manufacturers themselves.  Every plumber I know uses 60° as a minimum, real world figure.  Another thing to keep in mind: the Plumbing Code requires “hot water” to all fixtures for “bathing, washing, culinary purposes…etc.  The Code defines “hot water” as “greater than or equal to 110° F”.

OK, if all of these numbers are making your head hurt here’s the bottom line.  A standard shower head uses at least 2.5 GPM (gallons per minute).  The biggest residential electric tankless can deliver less than 5 GPM at a realistic temperature rise.  That means if two shower heads are running at once they will have less than full flow.  Since one of the most common complaints I hear is that the showers don’t have enough pressure already, this is just a recipe for dissatisfaction.

But that’s not all.  This lackluster performance comes with a price.

Electric tankless water heaters require an enormous amount of electricity as compared to any other equipment in the home.  The largest models require a whopping 160 amps. With most new homes having a 200 amp electrical service, that’s 80% of the total electrical capacity of the home.  Many older homes don’t even have a large enough electrical service to power the tankless, much less the rest of the house.

In case you think I’m just ranting, I’m not alone.  Electric Utilities hate electric tankless water heaters.  Since they make money selling electricity you would think they would love them.  It seems that they use so much power that they can overload the system.  Check out this excerpt for Progress Energy’s website on tankless.  (Progress Energy is a power utility that services most of Florida.):

“•  The new load of a tankless water heater can sometimes equal the load of an entire new home!
•  …if a customer installs a tankless water heater, the increased electric demand may exceed the design specifications of the system and require an upgrade of the cable and transformer. … will be charged directly to the customer. & If a customer installs a tankless water heater, the customer is required by approved tariff in both the Carolinas and Florida to pay the full cost to upgrade their facilities (including cable and transformer) to meet the need.
•  Customers complaining about a voltage fluctuation or flickering lights may be seeing the impact of a tankless water heater in their neighborhood. It is important to note that this voltage fluctuation may be noticed by other customers in addition to the customer with the tankless water heater – since several customers often share a single transformer. An investigation of all customers on the transformer may be necessary to determine the source of the problem. & If voltage problems exist because of a tankless water heater and a facility upgrade is necessary, the customer with the tankless water heater is required to pay the full cost to upgrade prior to construction.”

I don’t know if this is actually enforced but it is pretty plain to see that this Power Company is definitely trying to discourage the use of electric tankless water heaters.

Look, I do not have an axe to grind against the electric tankless industry.  There are even a few situations where a small electric tankless might make sense.  I just don’t think they are a good choice for a whole house water heater.  I also want to make sure that you can count on me to give you the real, no hype truth in this blog.  And, in this case,  I think electric tankless water heaters are a bad choice in most cases.

And now that I may have alienated some of you who may even have an electric tankless (I promise it’s nothing personal), maybe I can make it up to you with a little cartoon.  I found this on YouTube and my boys thought it was hilarious so I thought I’d share it with you.

I hope you liked that. I have some new “Green” stuff I am researching right now so keep checking back for some cool info.

Until next time,

Bryan Stevens

Copyright 2009 Bryan Stevens

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6 comments to Electric Tankless and Another Funny Video

  • Hi – I am so delighted I found your blog, I really found you by accident, while I was researching on Digg for something else. Nonetheless I am here now and would just like to thanks for a fantastic post and an all round interesting blog (I also love the theme/design).

  • Jed

    I see you point, but I use them in commercial invironments where there is no person taking a shower or the like. Most folks in this environment are washing there hands or washing a coffee cup. I can’t tell you how many banks have replaced a 50 gallon water heater, for what????? The sothern states would be logical as well. Everything has it’s place, they may not be logical in Alaska or a house hold of 3 to 5. Add common sense, and urica.

  • Thanks for given this post.

  • admin

    Hey, thanks! I’m glad you like it. I am working on some things that I think will make it even better over the next few weeks, but I really want to know what you would like to see on the site. Please let me know if there’s anything in particular I can help with.


  • I just wanted to say that I love this site

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