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Tankless Water Heaters are Brutal on the Grid When Popularized
Tankless water heaters draw energy on demand, and do not have a thermal
energy storage facet. Multiplied by many customers' hot-water usage
patterns, these surges of energy amount to a significantly higher peak load for
utilities, resulting in increased costs and, more significantly, in increased
waste during non-peak times.
the United States, the amount of energy vented (wasted) every day by the
utilities due to lost energy of non-peak production, is enough to run all of
the vehicles in the country."
D. Allan and Paul
Pure Energy Systems News - Exclusive
Copyright © 2005
While tankless water heaters do indeed usually provide
a customer with substantial out-of-pocket savings on their fuel bill, a problem
arises when a lot of people use such a system. It puts a heavy load on the
grid during peak times.
Individual customer savings may be high, but a lot of customers using the system
results in increased costs for the grid due to a net increase in energy
generation required due to the increased peak load spikes.
Tank v Tankless from the Grid's Point of View
Compared to the tankless systems, tank-based water heaters are energy hogs
because they have to maintain that tank of water at a high temperature during
long periods when no water is needed. Though insulated, there is still a
constant loss of heat energy into the environment.
The most obvious waste is during those times when a family might be away on
vacation. But even the spans at night while the family is resting, or
during the day while they are away from home, the water heater churns away,
keeping that tank of water hot.
"On-demand", tankless systems, on the other hand, heat the water from
cold to hot as it is needed, and then shut themselves off. There is no
interim period of waste of heat into the surroundings, other than the water
between the heater and the fixtures.
So yes, you can see why the "on-demand", tankless water heater system
would save as much as 60% over the tank-based water heater when compared side by
But now think of this in terms of the electrical grid, and you will see that the
collective use scenario creates a problem.
The water tank system, though inefficient for the consumer, serves as an energy
storage system as far as the grid is concerned. It buffers the energy
consumption away from peak energy load times. Peak usage is still the
same, but the energy required to heat the water is spread out over a much wider
period of time. The tank of hot water serves as thermal mass storage
unit. It is already hot when you jump in the shower in the evening, and
then tops off as you shower and after you get out, for example.
Tankless systems, on the other hand, draw a large spike of power demand during
times of use. The overall usage may be 60% less, but the spikes are much
higher. The tankless system has to heat that water from cold up to hot
during the time that you are showering, for example, not before or after.
Multiply that by many thousands of people in a municipality, and you create a
real problem for the electrical generating utilities.
Utilities Have to Match Peak Requirement, and Vent During Non-Peak
Utilities have to build and maintain their systems to handle peak load -- that
time when people tend to use the most energy, such as at night as people return
home, turn on their lights, cook dinner, run their washers and dryers, turn on
their televisions, vacuum the floor.
The utility needs to have enough electricity ready to go so that when you turn
on your switch, the electricity flows immediately. Collectively, that
means that the higher the peak load, the larger they have to build their plants
to handle those peaks.
In Florida, where tankless water heaters have been around for about 20 years,
and have become quite popular, the utilities are seeing fourteen times as much
energy consumed during peak as during the base load rate. In their case,
it is not considered a "peak" but a "spike", that spike
having been created by the use of tankless water heaters.
Now here is the real kicker. You and I might think that the grid is kind
of like a rheostat. If you need more power, you turn it up, if you need
less, you turn it down. Who cares if you need more power at one time, and
less in another, as long as the overall usage is less, right?
Grid production is similar to
continuously-running drinking fountain. It's on, whether or not you
are taking a drink.
That is not how the grid operates. Once you fire up a nuclear power plant,
it is running full bore. Period. No up or down, just on -- full
You can't just flip a switch several times a day to turn a 500 MW coal or gas
generator on or off. They are designed for continuous running. They
run the best (are most efficient and clean) at full throttle.
What that means is that much of the non-peak energy being generated, that is not
being consumed, is vented into the environment. It is wasted. Not
used. Spilled. Kaput. Gone.
It is like one of those drinking fountains you sometimes see in a public
park or walkway -- continually running, whether or not someone is taking a
Now here is a statistic for you to put in your top ten things to remember about
energy. In the United States, the amount of energy vented (wasted)
every day by the utilities due to lost energy of non-peak
production, is enough to run all of the vehicles in the country.
| "This vented or wasted
energy could be instantly vectored into Hydrogen Cracking and pretty
well drive our vehicles .... if we confront big oil head on. There
is our 'Hydrogen Economy' ready to rock and roll." -- Paul
(But that is another story)
Bringing Down the Peak
What we need to be thinking about, therefore, to facilitate a very substantial
overall planetary reduction in energy pollution, is to even out the peak-base
grid demand through a combination of two things. One way is for customers
to conscientiously change their usage patterns, such as to delay running washing
machines and other high-demand machines until later at night.
The other is through discovering, optimizing, and installing methods by which
energy from off-peak times can be stored for use during peak times. That
way, utility energy generators can run at full throttle, which is where they
operate the most efficiently, and the non-used energy will not be wasted.
In this way, the difference between peak and base is nearly eliminated; and
proportionately, the amount of waste is likewise slashed.
There will be some losses any time energy is converted from one form to
another. No storage system is 100% efficient. So the complete
eradication of the peak-base humps is not likely to ever be achieved. But it can
be approached. Awareness of the problem is a key in resolving the problem.
Another solution is for each household to become
grid-independent. Small-scale generators are much more likely to be able
to handle "on-demand" production and not require continual running at
the same speed. And battery storage is widely used to even out production
from intermittent sources.
So are Tankless Water Heaters Bad?
In order for a tankless water heater to decrease the overall footprint of energy
pollution on the planet, it needs to be used during off-peak times. Then
it is contributing to an overall solution. Those who use it during peak
times are contributing to the overall problem, not helping.
A General Principle
And really, that goes for all appliances. The tankless heater is but an
example of a principle.
One of the most effective things people can do to do their part individually to
reduce the overall dependence on oil, is to shift their energy usage patterns
such that they are conscientious about when they are using their
appliances. Can you do your laundry during the day, rather than in the
evening? Or later at night? Turn your dehydrator off during peak
hours. Perhaps you could put some of your appliances, such as a dehydrator
or swimming pool heater, on a timer, to turn them off during peak hours.
If such timing devices are not readily available, let's call upon our major
suppliers to stock them and promote them. Give them a copy of this
article. And while you're at it, pass a copy on to your friends and
associates. Send one to your elected representatives too!
The idea is to bring down that spike on the grid. Every bit we can do that
together will mean that the utilities can cut down on their energy generation
capacity, and not vent so much wasted energy during non-peak times.
This one thing could be the biggest thing we could do together as a
society to help with the energy crunch, without really effecting our overall
quality of life.
Let's do it!
# # #
Northern Climate Unsuited to Tankless Heating
Haliburton, Ontario, Canada
Two issues are important when making a decision about going tankless for hot
water. One is temperature differential, and the other is flow rate. I spoke with
a local plumber, David Sparling, noted for high integrity and good service.
He explained how these systems are suitable mostly for the south-temperate zone.
If you live in the South, the water coming in to your household pipes is likely
to be about 60F for most of the year. A temperature differential gain from the
tankless heater of fifty degrees will then bring it up to 110F, suitable for a
warm shower. A flow rate of 3 gallons per minute is enough for a small
household. This would allow use of the lower priced mini units, and achieve
significant cost saving.
However, if the water coming into your house is only 40F -- as it usually is
during the winter in Canada and probably some northern states -- then what comes
out of the tap would be only 90F if put through this lower-powered tankless
heater. This is below body temperature and a trifle cool for a shower. And if
taking a tub bath, this would feel downright chilly.
In order to get the water up to 110 degrees, you would have to get not only a
higher flow rate but also the 80-degree differential heater, which is a bigger
unit and much more expensive -- about $3,000 Canadian installed. This is nearly
double the price of installing a hot water tank heater. According to Mr.
Sparling, an electric tankless unit of this capacity needs a cable the thickness
of your arm, of the type that used to be installed with the 1980s-vintage
electric furnaces, and, of course, a circuit box capable of supporting it. This
means that the high-differential unit would also consume a lot more electricity,
and would not save much on the energy bill, if anything, compared to an electric
Mr. Sparling also indicated that in his experience, gas is more efficient than
electricity in these on-demand setups, especially the large-capacity ones. Since
the flame is instantly full on, the heating occurs faster than with electric
elements which take time to get warmed up.
So, if you are in a geographic region where the temperature differential would
be fifty degrees or less, it may save you some money to go tankless; just use it
in off-peak hours.
However, there are regions where this is not going to save you any money. Your
local plumber can probably advise you about the best options.
Page composed by Sterling
D. Allan Oct. 18, 2005
Last updated December 24, 2014