Energy Efficiency

Published on February 9th, 2015 | by Peter Young


How Gas And Electric Water Heaters Work


Did you know that water heaters are typically the second biggest user of electricity in your home? It’s true, central A/C systems come in at #1, but not far behind at #2 is your water heater. After all, literally every ounce of hot water you use to take showers, wash clothes and dishes, etc. has to run through it at some point. According to the Hawaiian Electric Company (HECO), the average family of four will spend roughly $986 per year to heat the water they use throughout their home. That’s a ton of money! Fortunately, your water heating costs don’t have to be that high, and a great way to prevent them reaching such heights is with a basic understanding of how your water heater works.

How gas and electric water heaters work

Both gas and electric water heaters work the same way to heat water, so if you have an understanding of one you’ll be able to understand the other. To start, take a look at the following diagram (of a gas water heater) to familiarize yourself with the various parts of the water heater:

Screen Shot 2015-02-05 at 2.55.10 PM

Essentially, the water heater works by taking in cold water through the cold water inlet, once it’s in the tank it’s a matter of basic physics. The cold water sinks to the bottom (since it’s denser than hot water) where it gets heated by either a gas burner or electric heating element. As the water is heated it rises (since it’s less dense than cold water) to the top of the tank where it is eventually drawn out of the hot water outlet when you take a shower or wash a load of laundry. Voila!

The other commonality between gas and electric hot water heaters is the anode rod. In most cases the anode rod is made up of magnesium, aluminum or zinc, and the rod’s job is to serve as sacrificial lamb that protects the lining of the tank. Typically when water and metal get together the water will wear down the metal and eventually cause it to rust and break apart, which is the last thing we want to have happen to the interior walls of your hot water tank. The anode rod will help to prevent this from happening since it is comprised of a less noble metal than the water tank (commonly made out of steel). So instead of attacking the walls of the tank, the water corrodes the anode rod.

The difference between a gas and electric water heater

The biggest difference between a gas and electric water heater isn’t in how it heats the water, but rather it’s the mechanism it uses to heat it. In the case of a gas water heater, the system will use a burner (much like the ones you’ll find on a gas stove top) to fuel a flame which heats a plate that heats the water. In systems such as this it is necessary to have a vent pipe that leads outside the home since a hazardous by product of the heating processes is carbon-monoxide.

In the case of an electric hot water heater, there is no flame or carbon-monoxide in the equation, and therefor no need to vent hazardous gases out of the home. Instead the water heater uses electricity to heat up an electric element to heat the water.

How to make your hot water tank more energy efficient

Regardless of whether you have a gas or electric hot water tank there are many inexpensive ways that you can make them more energy efficient. Just try implementing any of the following home improvement projects:

If you’re looking for more ways to save money and energy around your home, be sure to check out our green home improvement projects: Green Living Ideas, after all, is a top 20 home improvement website!

Photos courtesy of the flickr creative commons (water heater),,

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About the Author

graduated from Pacific Lutheran University (PLU) with a degree in journalism and has made sustainability and eco-conscious living mainstays of both his professional and personal life. It was during his time at PLU that he began his journey with sustainability and it's what has led him to writing for Green Living Ideas. He currently resides in Honolulu and works for Pono Home, an energy efficiency company focused on reducing carbon emissions and promoting a healthier, greener lifestyle.

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