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Everything Old Is New Again

October 11, 2011
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New York City is home to one of the most unusual museums in the world, the Tenement Museum in lower Manhattan.

This museum preserves some of the apartment buildings, known as tenements, where people from all over the world began their new lives in America more than 100 years ago.

Conditions in these tenements were meager, to say the least.

Located in the kitchen and bathroom of each apartment was a rectangular box hanging on the wall.

Along with paying for water and electricity, tenants would place a quarter in one of these boxes and, for about two hours, the box generated hot water for washing, bathing and other personal needs.

These boxes were the original tankless water heaters.

And, while we may no longer have to put a quarter in them, tankless water heaters have been making a big comeback in the past few years because they can help significantly reduce energy consumption.

Hot Water Demand Periods

Until recently, most people did not realize just how energy inefficient a typical hot water heater is.

Studies indicate that in two-income homes and apartments without children, the hot water demand period — when hot water is most often requested by building users — is about two hours in the morning and about three in the evening, a total of five hours per 24-hour period.

Yet, most conventional water heaters are designed to maintain what is called standby hot water 19 hours per day.

The tankless heater requires energy only during the hot water demand period, whereas the conventional "tank" hot water system requires energy virtually throughout the day, whether hot water is requested or not.

Similar studies of hot water demand periods have been conducted in restaurants, office buildings, schools and even sports arenas.

In restaurants, hot water is typically requested about nine hours per day; although there can be variables, in schools and office buildings, the demand will fluctuate but is also likely to be around nine hours per day.

A sports arena may only be used two or three times per week for three or four hours at a time, yet hot water is being produced essentially 24/7, whether it is needed or not.

One does not require a calculator or computer spreadsheet to see the potential energy and cost savings that are possible if a hot water system is operated only when necessary instead of on standby throughout the day.

It is believed tankless systems improve the energy efficiency of a home or commercial facility from eight percent to as much as 50 percent, depending on the amount of hot water demanded, which can translate into energy savings of 10 percent to as much as 30 percent.

This is why tankless hot water systems are becoming increasingly popular not only in homes and apartment buildings, but also in commercial facilities that are focused on being greener and more sustainable.

Other Advantages And Potential Disadvantages

In addition to energy savings, there are other benefits to tankless hot water heaters.

Although they have gotten larger in recent years to increase water capacity and meet greater hot water demand, they are still very small and compact when compared to a conventional tank water heater.

In fact, most builders and facility managers believe one of the key advantages of a tankless system, in addition to the energy savings, is the space savings.

Another advantage is that, in most cases, a tankless system can provide unlimited amounts of hot water and do so instantly.

However, in large commercial buildings, multiple tankless systems may be necessary to meet hot water demand.

Also, extreme cold weather can impact the actual heat of the water — at least initially — and how hot the water is when first requested.

In some cases, it may take a couple of minutes for hot water to pour from the tap.

This, however, may be about the same amount of time it takes a traditional tank water heater to provide hot water at various taps.

Another potential disadvantage to tankless systems is expense.

While costs continue to come down, in many cases, tankless systems do cost more than conventional hot water heaters.

It is believed that, over time, competition and the streamlining of production will help lower costs for these units.

Further, the potential energy savings will likely mitigate the larger price tag over time.

Additionally, even though they offer space savings as a key advantage, tankless systems can be costly to install, especially in a preexisting facility.

This can run a few hundred dollars in a home to several thousands of dollars in a commercial location.

Finally, a tankless system may have more maintenance issues than a conventional hot water heater.

According to a Consumer Reports study, tankless systems do require more routine service than conventional water heaters, which can go years with little or no service.

This is because of calcium buildup in the tankless unit, which can reduce the efficiency of the system, constrict water flow and, if not attended to properly, damage the unit.

Tankless hot water systems have come a long way from those installed in the tenements built a century ago.

In fact, they have come a long way when compared to the systems developed just a decade ago, and the industry and technology are still evolving.

However, it would not be surprising to see tankless systems, at least in homes and smaller commercial buildings, become the most common way to heat water in the next few years.

Robert Kravitz is a writer for the professional cleaning, building, hotel, hospitality and education industries. He may be reached at

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