Understanding Water Heater Efficiency Ratings: What Do They Mean?

Understanding Water Heater Efficiency Ratings: What Do They Mean?

When you are out shopping for a new water heater, you may be surprised to hear terms like “energy factor (EF) rating” and “uniform energy factor (UEF) rating.” But what do they mean? In this article, we will break down the basics of water heater efficiency ratings to help you choose the right unit for your home or business. Read on to learn more.

Understanding Water Heater Efficiency Ratings: What Do They Mean

But before we explain what EF and UEF are about, we would like to inform you that Silco Plumbing has been providing plumbing services for over 30 years. Get in touch with our team of professionals for all your water heater needs. We would happily help you choose the right water heater for your home or business. Contact us today!

EF Ratings Used to be The Standard

Prior to June 1997, the energy factor (EF) was the standard rating used to measure water heater efficiency. This number indicates the amount of energy that goes into heating water divided by the total amount of fuel consumed. In essence, it is a measure of the input-to-output ratio.

The EF rating for most modern water heaters can range from 0.5 – 0.6 and higher ratings usually indicate more efficient units that cost more upfront but will save you money over time.

However, the Department of Energy (DOE) decided that the EF rating did not accurately reflect what people expect from their water heaters nowadays and also did not give a solid comparison of different water heaters. In order to address these issues, the Department of Energy created the uniform energy factor (UEF) rating system.

UEF Ratings Are The New Standard

In June 1997, uniform energy factor (UEF) became the standard rating for measuring water heater efficiency. This rating is a combination of EF and overall water use. UEF ratings measure how much energy goes into heating water and how much hot water that unit produces.

The UEF rating system is more comprehensive than the EF rating. It takes into account standby losses (the heat that escapes when it’s not in use) and cycling losses (heat that escapes during heating cycles). This allows for a better comparison of different water heater models to help consumers find the most efficient one.

So, when you are out shopping for a new water heater, look for the uniform energy factor (UEF) rating and ask questions about how it compares to other models. This way, you can make an informed decision that will save you money today and in the long run.

UEF Ratings And Energy Star Certification

Energy Star is a program initiated by the federal government that certifies energy-efficient water heaters and other products. A product must meet certain standards set by the Environmental Protection Agency (EPA) in order to be certified with the Energy Star label.

This is where UEF ratings come into play. In order for a water heater to be eligible for this certification, it must have an impressive UEF rating. So, if you see the Energy Star label on a water heater model, you can rest assured that it is energy efficient and will save you money over time.

Example UEF Ratings

The range of UEF ratings for gas and electric conventional tank water heaters, as well as gas tankless water heaters, is between .60 and .93. Electric tank, tankless, and high-level gas tank water heaters have UEF ratings that are closer to the top of that range.

The highest efficiency rating is given to heat pump water heaters which range between 2.0 and 3.2. This means that these water heaters will provide you with the most energy savings in the long run but also cost more upfront. The new hybrid heat pump water heaters have UEF ratings of about 3.5, which is not unexpected.


Now that you understand more about water heater efficiency ratings, you can use this information to make an informed decision when shopping for a new unit. Don’t forget to ask questions about UEF ratings and Energy Star certifications to ensure you are getting the most out of your purchase.

However, you should be aware that a water heater’s UEF rating is not the only factor to consider when making your decision. You should also look into the size, warranty, availability, cost of electricity and natural gas, installation cost, and other features that may be important for your home or business.

That is why you need the assistance of a licensed plumbing contractor, such as Silco Plumbing, before making a decision. Our knowledgeable team of professionals will help you find the perfect water heater for your needs. Contact us today to schedule an appointment!

Silco Plumbing is Here to Help

If you have any questions about water heater efficiency ratings or need help finding the right unit for your needs, don’t hesitate to get in touch with Silco Plumbing. With over 30 years of experience in this field, we can assist you with all your water heater needs. Contact us today at 781-438-8925 for more information! We look forward to hearing from you.

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