Tankless Truth: Tankless Water Heaters Work Well with Cold Inlet Temperatures

With the benefits of high efficiency and fast recovery, tankless can provide businesses with the hot water they need no matter where they are in North America.

by Tim Greer 

Wherever temperatures get below freezing, an often-preconceived notion is that tankless water heaters do not work well with cold groundwater temperatures. This is a prevalent misconception in northern states, such as Minnesota, Wisconsin, the Dakotas, etc. These biases have caused many buildings to be designed without consideration of tankless technology. However, by providing a design recommendation based on myth, MEP engineers could be missing out on the many benefits a tankless water heater could provide their clients.

Here’s the Tankless Truth™: tankless water heaters work well with cold inlet temperatures, and below are several proof points to dispel some of those preconceived notions an engineer might hold.

Gas vs. Electric

In colder climates, a gas tankless water heater is the best option, as gas typically outperforms electric tankless water heaters, and most gas tankless models perform well with groundwater temperatures as low as 40°F. Case in point, more than 100,000 gas tankless water heaters are sold in Canada per year. If tankless units are proven to work in Canada, where groundwater temperatures are as low as 38°F or 3°C, they can handle similar climates in northern U.S. states, providing adequate amounts of hot water when needed for a business to function.

The Benefits Tankless Provides Your Clients

Tankless units can keep up with demand despite cold inlet temperatures and provide further efficiencies for your clients’ buildings and businesses to be productive.

Cost-Cutting Efficiencies

Many standard commercial tanks have a thermal efficiency below 70 percent, whereas noncondensing tankless units are 80–85 percent thermally efficient, using less fuel and energy to function. These savings can add up, protecting your client’s bottom line. To top it all off, these increases in thermal efficiency often qualify for local government and/or energy provider rebates where traditional tanks may not—therefore lowering the total cost of ownership even more.

Tankless Can Keep Up with High Demand

With cooler groundwater temperatures, many believe it takes more energy and time to heat water to the desired temperature, thus reducing the amount of hot water available, but a single tankless model can provide 120°F water up to 5 gallons per minute (gpm) or more even with colder groundwater temperatures. For perspective, in a residential home, an average showerhead will deliver about 1.5–2 gpm; considering the average shower is around 105°F, this can equate to as much as three showers delivering unlimited hot water simultaneously.

Larger, commercial plumbing projects will often need more than three fixtures running concurrently, and tankless water heaters provide multiple solutions for these commercial plumbing projects. For example, a system that combines two tankless water heaters that can modulate between 15,000 and 398,000 Btu, such as Rinnai’s TRX Compact Wall-Mount System, distributes the load evenly as well as provides redundancy—greatly minimizing the potential for maintenance or service downtime, which could result in lost revenue for the business owner.

Considering that systems can combine up to 25 tankless units modulating between 15,000 and 4.9 million Btu, this type of flexibility and innovation can tackle virtually any commercial demand, even with cold inlet temperatures.

Tankless Can Recover Faster

The recovery time is much slower for a standard tank water heater and is amplified in cold groundwater areas. A 40-gallon tank can take upwards of 30 minutes to an hour to fully recover before hot water is available again, which could affect a business’s customer experience and ultimately revenue, as clientele may be experiencing cold water in showers or other fixtures. On the other hand, by design, when sized correctly, tankless water heaters will provide continuous hot water, which delivers peace of mind and a better bottom line for any business owner.

Cold climates shouldn’t dissuade you from including tankless water heaters in your project designs. With the benefits of high efficiency and fast recovery, tankless can provide businesses with the hot water they need no matter where they are in North America.

About the Author

Tim Greer is a Technical Training Developer and instructor with Rinnai America.  With more than 20 years in the mechanical and electronics industries, he began his journey with Rinnai over 16 years ago. He has held various roles in technical support, commercial service, product management, and training development. To learn more about the other common myths associated with tankless water heaters, visit rinnai.us/tanklesstruths.

The opinions expressed in this article are those of the author and not the American Society of Plumbing Engineers.

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