Tankless Water Heater Savings
After my last blog, I got an email from a friend of mine, who is involved with the installation and sales of tankless water heaters. Here is what he wrote:
Bill,
I read all of your blog interesting but very negative on tankless, don’t agree with all of it but well written. where are the heating efficiencies, for example tank water heater is only 40 to 55 % efficient vs. 82 to 94% how about the clean water you get without all the junk from the tank, I have attached a picture from a tank that was only 10 years old, take a look. LOL. At the end what is more costly and important 10 to 20 sec. Additional delay of getting hot water and may be 2 gallons of water or the inefficiency of the tank water heater and the additional energy wasted and environmental impact. Oh well, I could go on. LOL
Al
So in response to Al’s email…
First off, who has a 40 to 55% efficient water heater?
I poked around on the internet looking at water heater efficiencies, and could not find any water heater with an energy factor of less than .56. Most were .60 or more. (I presume we are talking about the energy factor when we refer to efficiency.)
I took a look at the tankless water heater specs and I found that most tankless units had energy factors of about .82. The highest I saw was .92, but I didn’t spend a lot of time looking so I probably just didn’t come across those .94 units.
So before moving on, I would like to say that using 40 to 55 percent efficiency for tank type water heaters is on the extreme low side. 60 percent efficiency would be the most common storage efficiency from my limited research.
I visited the ACEEE – (American Council for an Energy-Efficient Economy) who I think you could say is an independent 3rd party. They have a comparison table comparing Life-Cycle costs for the various types of water heaters.
Interestingly they recommend looking for a gas storage water heater with a minimum energy factor of .63 and they state that the highest is .67. Quite a bit higher than 40 to 55%.
From their table, a conventional gas storage water heater with a EF of .60 has a yearly cost of $350, and a tankless water heater with an EF of .80 has a yearly cost of $262.
As you can see the difference in yearly energy cost is 350 – 262 = $88.00 a year, or about $7.33 a month. A tad more if the efficiency was .82 as I was finding.
For me, $8.00 a month is definitely not worth the potential problems associated with tankless water heaters, and the changes in behavior I would have to make, like giving up that “trickle” of warm water I use when I brush my teeth. I hate cold water on my teeth!
As for the pictures of the corroded old water heaters… here are my thoughts. First, since I usually drink cold water, I am drinking the water from the water main. Since the water passing through the water heater also came from the same source of water, then it must be even cleaner than the cold water if it leaves all that stuff in the heater.
All that sediment and those deposits are just minerals that have come out of the water as it was heated, and you consume those same minerals every time you drink the cold water. So I don’t see a problem.
By the way, in areas with high mineral content many of the tankless water heater manuals instruct you to clean out your heat exchanger periodically. It seems the hard water is hard on tankless heaters too! Cleaning the heat exchanger on a regular basis does not sound like something I would want to do.
Metlund D’mand systems, our main competitor and the big guys on the block as far as sales go state that the savings from a demand hot water system from reduced water consumption and reduced sewage fees amounts to about $150 a year for a typical home with a natural gas water heater.
Gee… that’s more than the tankless water heater saves to begin with. If Scottsdale Arizona is offering rebates of $200.00 for homes that install demand hot water systems they must feel that the wastage of water from residential hot water plumbing systems is significant.
If you are really concerned about environmental impact, then you should put a hot water demand system on your tankless unit and more than double the monetary savings and reduce both energy consumption and water wastage. Pumping and treating water and pumping and treating sewage consumes energy as well.
Subtract that extra gallon or two of water from the savings provided by the increased efficiency of the water heater, and environmentally the tankless water heater doesn’t look so good. Just my opinion of course.
So Al, perhaps I have miss-interpreted your numbers, perhaps you weren’t referring to energy factor with your efficiency numbers?
That’s all for today folks…LOL…if anyone reads this blog.
Bill
Bill,
I read all of your blog interesting but very negative on tankless, don’t agree with all of it but well written. where are the heating efficiencies, for example tank water heater is only 40 to 55 % efficient vs. 82 to 94% how about the clean water you get without all the junk from the tank, I have attached a picture from a tank that was only 10 years old, take a look. LOL. At the end what is more costly and important 10 to 20 sec. Additional delay of getting hot water and may be 2 gallons of water or the inefficiency of the tank water heater and the additional energy wasted and environmental impact. Oh well, I could go on. LOL
Al
So in response to Al’s email…
First off, who has a 40 to 55% efficient water heater?
I poked around on the internet looking at water heater efficiencies, and could not find any water heater with an energy factor of less than .56. Most were .60 or more. (I presume we are talking about the energy factor when we refer to efficiency.)
I took a look at the tankless water heater specs and I found that most tankless units had energy factors of about .82. The highest I saw was .92, but I didn’t spend a lot of time looking so I probably just didn’t come across those .94 units.
So before moving on, I would like to say that using 40 to 55 percent efficiency for tank type water heaters is on the extreme low side. 60 percent efficiency would be the most common storage efficiency from my limited research.
I visited the ACEEE – (American Council for an Energy-Efficient Economy) who I think you could say is an independent 3rd party. They have a comparison table comparing Life-Cycle costs for the various types of water heaters.
Interestingly they recommend looking for a gas storage water heater with a minimum energy factor of .63 and they state that the highest is .67. Quite a bit higher than 40 to 55%.
From their table, a conventional gas storage water heater with a EF of .60 has a yearly cost of $350, and a tankless water heater with an EF of .80 has a yearly cost of $262.
As you can see the difference in yearly energy cost is 350 – 262 = $88.00 a year, or about $7.33 a month. A tad more if the efficiency was .82 as I was finding.
For me, $8.00 a month is definitely not worth the potential problems associated with tankless water heaters, and the changes in behavior I would have to make, like giving up that “trickle” of warm water I use when I brush my teeth. I hate cold water on my teeth!
As for the pictures of the corroded old water heaters… here are my thoughts. First, since I usually drink cold water, I am drinking the water from the water main. Since the water passing through the water heater also came from the same source of water, then it must be even cleaner than the cold water if it leaves all that stuff in the heater.
All that sediment and those deposits are just minerals that have come out of the water as it was heated, and you consume those same minerals every time you drink the cold water. So I don’t see a problem.
By the way, in areas with high mineral content many of the tankless water heater manuals instruct you to clean out your heat exchanger periodically. It seems the hard water is hard on tankless heaters too! Cleaning the heat exchanger on a regular basis does not sound like something I would want to do.
Metlund D’mand systems, our main competitor and the big guys on the block as far as sales go state that the savings from a demand hot water system from reduced water consumption and reduced sewage fees amounts to about $150 a year for a typical home with a natural gas water heater.
Gee… that’s more than the tankless water heater saves to begin with. If Scottsdale Arizona is offering rebates of $200.00 for homes that install demand hot water systems they must feel that the wastage of water from residential hot water plumbing systems is significant.
If you are really concerned about environmental impact, then you should put a hot water demand system on your tankless unit and more than double the monetary savings and reduce both energy consumption and water wastage. Pumping and treating water and pumping and treating sewage consumes energy as well.
Subtract that extra gallon or two of water from the savings provided by the increased efficiency of the water heater, and environmentally the tankless water heater doesn’t look so good. Just my opinion of course.
So Al, perhaps I have miss-interpreted your numbers, perhaps you weren’t referring to energy factor with your efficiency numbers?
That’s all for today folks…LOL…if anyone reads this blog.
Bill
Labels: energy conservation, environment, tankless water heaters
posted by Hot Water Guy at
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