Tankless (aka instantaneous) water heaters have been around for years mostly in commercial applications. Now the use of this technology in the residential sector is being widely advertised as saving the customer over 50% of their energy use. These comparisons are usually done against standard, lower efficiency, steel water heaters. Unfortunately, most residential customers are unfamiliar with this product and do not know the specific demands of this complicated equipment. There are many other issues that must be addressed before an apple to apple comparison can be made.

Think the tankless unit will last 51 years when it has only a “Warranted against manufacturer’s defect” warranty?

Installation costs for tankless may be significantly higher due to wiring or pipe upgrades

Service costs are MUCH greater for tankless
*Energy usage figures from Department of Energy website based on avg KWH of $0.08 cents

Marathon vs Tankless!

The biggest issue to the utility is the untimely load these units place on our system. Family sized units require 240 volts and up to 160 amps capacity to operate. In some cases the unit peaks up to 36 KW. In addition to the cost of the tankless heater (which is priced about the same as a Marathon® water heater) significant wiring upgrades are almost always required. Based on Diverse Powers’ standard best practices, a transformer upgrade may be required. Who should pay for upgrading this transformer to one that will be loaded less than 10% of the time?

Proper sizing is also a key issue. Tankless water heaters are sized by flow rate as measured in gallons per minute (GPM). The size of the unit needed is determined from your highest demand for hot water at any one time. The heat rise of the water is determined by the GPM required. In most cases if the GPM requested is 1.5 (a low flow shower or kitchen sink), the unit will raise the ambient water temperature by about 92°. However, should you need 4.5 or more GPM, the temperature rise would only be about 50°. That is if you have a unit that utilizes 36 KW of heat coils. As the demand on tankless heaters increases the rise of the water temperature decreases.

Tankless water heaters have limited capacity and in some cases, if demand is very high, a second unit must be installed. Water quality is another big concern. Most of these units are “Warranted against manufacturer’s defect” only. The warranty can be null and void if minerals from your water deposit on the coils of the unit. These deposits will shorten the life of the unit. Some manufacturers provide de-liming instructions when a warning light illuminates. In fact, to achieve the long life that the manufacturers brag about, you would just about have to have pure water.

The Marathon® water heater is much more capable of handling diverse water conditions across the country. If the Marathon® ever leaks, we will replace it FREE, no questions asked. The savings the manufacturers of the tankless water heater tout are based on standby loss of the entry level steel tank water heaters. The Marathon® only loses about 5 degrees in 24 hours. Take a look at our energy comparison of the Marathon® vs. the tankless on the right. We believe our members prefer to have a cost effective and hassle free water heater, with a Lifetime Warranty.

View our selection of Marathon Water Heaters.


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