How does Rachio 3 calculate ET for Flex Daily schedule


Rachio documentation states: “Flexible Daily schedules will record the estimated moisture balance of each zone using evapotranspiration (ET) data provided by your preferred weather station.” (

It also states: "Then, based on the weather station that your controller is utilizing (whether that be an official station or a personal station), we are gathering the following data on a zone by zone basis:

I suspect the ET value used by the Flex Daily schedules is calculated by Rachio using something like the PENMAN-MONTEITH EQUATION; so it seems like the above two quotes are incorrect: i.e., the evapotranspiration levels are NOT a metric provided by the PWS.

Can you confirm that the ET used by the Flex Daily algorithm is in fact calculated by Rachio from the PWS’s Precipitation, Minimum and Maximum Temperature, Solar Radiation, Wind, and Relative Humidity data?


Based on past posts on this forum, User selected PWS is used for precipitation only (normal Weather Intelligence, not Plus) . ET is calculated from more “official” weather stations with more reliable set of measurements (especially wind). The PENMAN-MONTEITH has been mentioned as the method to calculate ET. Search this community if you’d like to dig into it.

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Thanks @Kubisuro!

It would be helpful if Rachio updated the two erroneous articles I cite above for those of us that would like to understand how the algorithm works in detail.

Thank you @Kubisuro, spot on.

@sarachio - An opportunity to tighten up our documentation. Thank you!


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