Water Heater Efficiency: What You Need to Know


As the economy is causing the average homeowner to think about their monthly expenses, it’s no surprise that many are looking for more energy-efficient options. When it comes to your home’s water heater, there are many options on the market today. We’ll discuss whether it’s worth investing your hard-earned money in a water heater that is considered highly efficient.

Understanding Efficiency Ratings

Every water heater is given a specific rating so that consumers can make more informed decisions about their purchases. Traditionally, water heaters were given an Energy Factor (EF) rating. The higher the EF rating, the more energy efficient a water heater was. EF ratings were used until mid-June 2017 when manufacturers switched to a Uniform Energy Factor or UEF rating.

The UEF rating system is considered to be more accurate and consistent than the previous EF rating system. Think of a UEF rating as a ratio showcasing the amount of energy a water heater is able to translate directly into hot water instead of wasting it on powering the piece of equipment or heating the surrounding space. For example, a water heater with a UEF rating of .93 can turn 93% of its energy consumption directly into the production of hot water. It wastes only 7% on operation and surrounding heat loss.

Determining a UEF Rating

All modern-day water heaters are given a UEF rating, with the higher ratings translating to more efficient water heaters. To determine a specific water heater’s UEF rating, it’s first positioned in a category called a bin. There are four bins: very small, low, medium, and high.

Very Small

FHR Less Than 18 Gallons
Less Than 1.7 Gallons Per Minute


FHR 18 to 51 Gallons
1.7 to 2.8 Gallons Per Minute


FHR 52 to 75 Gallons
2.9 to 4 Gallons Per Minute


FHR Over 75 Gallons
Over 4 Gallons Per Minute

All water heaters undergo a Simulated Use Test, where the individual efficiency of each water heater is tested under specific conditions. This includes an initial test to determine the First Hour Delivery (FHD) of the water heater, which is essentially how much hot water it can produce within its first hour of operation. Then, the testing continues to monitor the water heater’s efficiency over a 24-hour period, using particular measurements like air temperature and use timing.

How Do UEF Ratings Affect Consumers?

While it can be interesting to learn how the government agencies work to determine the overall efficiency of a water heater, you may be wondering how this UEF rating affects you as a consumer. When shopping around for a new water heater, you’ll want to look at each unit’s UEF rating.

Remember that the higher the rating, the more efficient the water heater is at translating energy into hot water. The more efficient the unit is, the less money you’ll have to pay in operating costs over its lifetime as compared to similar capacity water heaters.

Typical UEF Ratings of Common Types of Water Heaters

It’s important to realize that there are many different types of water heaters on the market today. From tank-style to tankless water heaters and gas-fueled to electric, there are many options to consider. In general, each category tends to have a specific UEF rating. Some of the most common water heater types include:

  • Gas Tank Water Heater: .63 to .93 UEF
  • Gas Tankless Water Heater: .82 to .97 UEF
  • Electric Resistance Water Heater: .93 to .95 UEF
  • Heat Pump Water Heater: 3.30 to 4.10 UEF

Energy Star Ratings

As with any appliance on the market, the U.S. Environmental Protection Agency (EPA) will give out Energy Star ratings to the most efficient products on the market. This is to not only help consumers understand the products that they’re thinking of buying but also help to promote the investment of more energy-efficient appliances in residential settings. Here are the minimum Energy Star requirements for each type of water heater:

  • Electric Integrated Heat Pump Water Heater: 3.30 UEF
  • Electric Split System Heat Pump Water Heater: 2.20 UEF
  • Gas Storage Water Heater (55 gallons or less): .81 UEF
  • Gas Storage Water Heater (more than 55 gallons): .86 UEF
  • Gas Tankless Water Heater: .87 UEF
  • Solar Water Heater (gas backup): 3.0 UEF
  • Solar Water Heater (electric backup): 1.8 UEF

Expert Water Heater Service

Guaranteed Comfort Heating & Cooling offers expert water heater service for the entire Windsor, ON region. We can also assist with all your heating, cooling, heat pump, heat recovery ventilation system, air purification system, and ductless mini-split system needs.

Contact our team at Guaranteed Comfort Heating & Cooling for more information on our water heater solutions today!

Chris Egan


Chris Egan, owner of Guaranteed Comfort Heating & Cooling, brings over 35 years of HVAC experience. Dedicated to customer satisfaction, he delivers top-notch heating and cooling solutions.