A new, mandatory procedure for testing and rating water heater energy use went into effect in June 2017. Called Uniform Energy Factor (UEF), it was developed by the U.S. Department of Energy and replaced the Energy Factor (EF) rating that had been in place for several years. But while the law requires manufacturers to follow this new procedure, some contractors aren’t aware of it and aren’t using it in their customer communication. “Wholesalers have gotten used to it, but plumbers and contractors still have a ways to go,” according to Randy Oshiro, an assistant engineering manager with Noritz.

That’s unfortunate. Contractors’ reluctance to embrace the new rating is understandable — most don’t want to make business more complicated than it already is — but it’s also unfounded. The UEF creates the opportunity to simplify sales conversations by offering more accurate comparisons for your customers’ likely water use patterns across different water heating technologies and fuel types. And by helping set realistic customer expectations, using UEF can reduce the chance of complaints later on.

For instance, by providing energy use estimates that better reflect real-world usage, the UEF allows better comparisons between propane or gas water heaters and electric. Even though some propane or gas water heaters may have a higher upfront cost than an electric model, many plumbers recommend them because they cost less to operate, especially where there are high electric rates. The UEF rating quantifies that recommendation.

How UEF works

UEF addresses the growth of new water heating technologies. The old EF rating had become outdated because it didn’t make accurate comparisons between the different types of water heaters on the market. “With the old test procedure, it was difficult to compare the energy use of tank, tankless, and heat pump units,” Oshiro explains.

To understand why, you need to consider the two main variables the test takes into account:

  • The draw pattern, or how much water the household typically uses
  • How much water the unit will deliver over a specified period

The old EF test calculated energy efficiency by simulating just one hour of use­. Its estimate of how much hot water the unit could supply was based on the draw pattern — or daily hot water use — of a “typical” user. In other words, it lacked specificity.

“Organizing heaters [into draw patterns] ensures that a heater designed for a mobile home is not compared to a model meant for a mansion.”

The new UEF test compares a water heater only to others with similar draw patterns. The categories, called “bins,” specify whether a unit is intended for households with very low, low, medium, or high hot water use. Manufacturers say this is a big improvement over the old rating. “Organizing heaters [into draw patterns] ensures that a heater designed for a mobile home is not compared to a model meant for a mansion,” says Joshua Greene, A. O. Smith’s vice president of government and industry affairs.

In addition, the energy efficiency number is now based on a 24-hour period. The test still makes assumptions about usage patterns when generating this number, but those assumptions vary by draw pattern. That’s because a typical family of five will use more water for a wider variety of reasons than the average single person or couple. The result is a yearly energy cost that better reflects the real world.

Units still have a yellow Energy Guide sticker. Interestingly, the sticker itself doesn’t display the UEF, but it now specifies whether the unit is intended for households with very low, low, medium, or high hot water use. It also assigns an estimated usage number to each level: for tank-type water heaters, that number is the first hour rating, or hot water delivered for the first hour of use; for tankless, it’s a gallons per minute estimate. The sticker also prominently displays the more accurate estimated yearly energy cost.

The Energy Guide sticker for water heaters now specifies whether the unit is intended for households with very low, low, medium, or high hot water use, and it prominently displays a more accurate estimated yearly energy cost. The label for the A. O. Smith condensing tankless water heater with integrated recirculation pump is pictured.

Gauging water use

Another advantage of UEF is that the one-hour rating it assigns to tank-type heaters addresses the bigger-is-better fallacy. A lot of consumers assume that a bigger tank will deliver more hot water, but the fact is that a smaller tank with a better burner could actually deliver more. According to the Rheem website, “a water heater with a nominal 40-gallon capacity could have a first-hour rating of 84 gallons, while one with a 50-gallon capacity might only deliver 81 gallons.”

Hot water delivery rates can also vary by fuel type because propane and gas water heaters have a faster recovery time. A 40-gallon propane unit and a 50-gallon electric unit would deliver the same amount of water in the first hour.

The Energy Guide label for tank-style water heaters, such as A. O. Smith’s ProLine standard tank-type gas water heater, displays the first hour rating, whereas labels for tankless water heaters show gallons per minute.

The contractor’s first job now becomes determining the customer’s hot water usage, or draw pattern. Note that household size isn’t the only criterion. A large family will certainly need a high-usage unit, but a smaller household might use more hot water than others of its size.

Greene says there’s no need to go into much detail about the new rating when talking with customers. “Most will either be bored or utterly confused if you dive too deeply into UEF,” he says. “But they’ll appreciate the fact that the new standard more accurately measures the first hour rating of hot water for [their draw pattern]. And they’ll definitely be grateful when you provide annual cost-of-operation data that’s more reliable than the estimate on the [old] Energy Guide label.”

A great place to start the conversation is with our climate-specific fact sheets analyzing the energy performance, economics, and emissions of different water heating types in cold, mixed, and hot climate zones. With this analysis and the simplified comparison tool of the UEF, you’ll be equipped to help your customers select the right water heating systems for their projects.


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Charlie Wardell