How Effective are ET Controllers?

The study noted two interesting points:

The Water-Saving Results Were Mixed

This study definitely demonstrates that irrigation controllers, used in the right circumstances, can save water. It’s also important to understand, however, that “weather-based, smart irrigation controllers, while a valuable tool, are not a ‘magic bullet’ for achieving perfect irrigation control and water savings.” Here’s why:

accurate weatherset etcontroller smSo even if you install an ET controller, and it uses localized weather data to change the amount of water delivered to your landscape each day, if your irrigation system has been installed and designed improperly, chances are high you’ll see dry, straw-like dead spots in your lawn that will eventually cause you to override the controller and pour on more water than you theoretically should.

The Need for Analytics

ET controller rebates and education programs are a common offering part of many water provider’s conservation initiatives. If the key success factors for ET controllers are:

…then it follows that water utilities will want to know which of their customers meet these criteria. That’s where analytics can be invaluable.

Using statistical data analysis to review each of your customer’s water usage history and factoring in historical ET and irrigable landscape data (gleaned from GIS or other sources), you can uncover who the over-irrigators are. Targeting your ET controller rebates to these customers first will generate measurable water savings, build momentum for your conservation program, and be a wise use of your conservation dollars.

How Much Water Could be Saved?

The research study measured the following outdoor water savings:

The study also found that 959 sites increased their water usage.

A Comprehensive Study

The research paper is very comprehensive and includes a wealth of information about:


ET controllers can be a powerful water conservation tool. The trick to generating measurable water savings is to target properties that are over-irrigating. Next, you want to inspect their existing irrigation systems to make sure they have been designed and installed correctly. Finally, the customer needs to be educated on how to properly set and use the equipment. This combination of steps will lay the foundation for a successful ET controller program.

A link to the full research paper can be found here: Evaluation of California Weather Based Smart Irrigation Controller Programs (PDF).

This paper was prepared by Peter Mayer, William DeOreo, Matt Hayden, and Renee Davis of Aquacraft, Inc., Erin Caldwell and Tom Miller or the National Research Center, Inc. and Dr. Peter J. Bickel and first published in July 1, 2009.