Here’s the PWS I’m using http://www.pwsweather.com/obs/KC6MLR.html
It looks like Rachio’s weather provider isn’t providing ET data (even if the PWS itself has it calculated and can be accessed). I did read somewhere that Weather Underground developers are making the ability for PWS to display ET data a priority for 2017 (but I’m not sure if WU is going to calculate it or they’ll pull ET data from PWS that calculate it). Of course I understand adding WU would be another licensing fee for Rachio.