Why Are Annuals Given 0.11 Daily in of Crop EV in the Middle of Winter?


On a sunny but Winter day, my zones ‘growing Annual’ are assigned 0.11" of Crop Evapotranspiration for the day. And on a cloudy day, still during winter, these zones get approximately 0.04". Why is this? Why so much?

Thank you.

Best regards,


As I look at this in more detail, it does not appear that in auto mode, ‘crop evapotranspiration’ is a function of much more than cloudiness.

I’m not seeing where crop evapotranspiration is influenced by outside temperature or time of year. And thus you get significant drops of CE on sunny days even though it may be near freezing and in the middle (Dec.) of the non-growing season.

I didn’t realize until now that ‘auto’ does not take into account outside temperature or time of year (growing season or not).

Best regards,



Hey @a0128958-
Sorry for the delayed response. I am a little confused about your question, one thing I can say is crop coefficient does not change seasonally. Do you mind maybe sending me the chart from your moisture graph so I can see the figures you are referring to?
McKynzee :rachio:


My question is WRT the after-ther-fact ‘Crop Evapotranspiration’ values that you show on the ‘More Detail’ ‘Moisture Levels’ chart:

Previous Moisture Balance
Irrigation (+)
Precipitation (+)
Crop Evapotranspiration (-)
Current Moisture Balance

I’m having difficulty understanding why CE isn’t near zero these days - constantly - for ‘Annual’ plant type - it’s the month of Dec., and it’s cold.

For example, on a sunny day I recently had a 0.11" value. It’s like CE ignores everything except how cloudy the day is, regardless of time of year or outside temperature. Surely ‘Auto’ mode is smarter than this?

Thank you.

Best regards,



Hey @a0128958-
I understand more now, thank you for elaborating for me! So that CE does not change through the year- this is a feature we had and then actually discontinued. That in conjunction with seasonal shift caused a lot of confusion with users, it was difficult to understand the two shifts and to differentiate them. The change in watering was pretty negligible, especially considering that many people are no longer watering when that crop coefficient basically plummets. However, I understand how that doesn’t make much sense once you hit these winter months, especially with your annuals. They should really need next to no water now, right? I know you are in a warmer climate, do some of your other plant types stay green this time of year? You should see us here in CO, it’s all either dead and brown or completely white with snow!
McKynzee :rachio:


I think this is a serious shortcoming of the Rachio product.

The fact that the daily calculation mechanism of CE does not change throughout the year says that the Rachio product assumes plants need just as much water when it’s 40 degrees F in the non-growing Winter season as they do when it’s 95 degrees F in the Summer season. And for which we know it isn’t true.

So the Rachio product is not a ‘set and forget’ product. It either works fine unattended during the Summer growing season or works fine unattended during the Winter growing season.

But not for both Summer and Winter. If a user’s objective is to put down the least amount of water with a ‘set and forget’ philoposphy for the entire year, then the Rachio product line isn’t there yet.

Best regards,



@a0128958, jumping in on this thread as I understand your concern but respectfully disagree with your last comment. The CE can/does change in some vegetation types due to the plant’s growing cycle. This is very common in agriculture as crop’s are grown to maximize yields while water is an input that needs to be carefully managed to control costs. This was originally built into our Flex Scheduling algorithms, but removed in May 2016 (see this support article for details). However, as @mckynzee mentioned, the monthly change to CE caused a change in the watering duration for some users that were already having difficultly dialing in the interval of the schedule they expected, so we simplified the logic for all new schedules moving forward with the goal of making schedules easier to manage for our users.

When using a Flex Schedule, the daily ET will drive the watering interval on a zone by zone basis. As such, whether it’s warmer or colder, the CE is used to calculate the watering duration, not the interval. While a standardized CE might not decrease the watering duration in some months, the interval will be accurate to the actual weather you’re experiencing. Compared to traditional timers and most other ET controllers that use only historical ET data for all scheduling perimeters, I still believe a Flex Daily schedule will be 80%+ more accurate for 20% the time time and cost.

Looking ahead, I’d love to hear your thoughts on how CE inputs and dynamic changes could be improved. We have a number of ideas we’re brainstorming internally, but maybe you’ve thought of a few solutions that you’d like to share with us?

Best, Emil


Thanks Emil.

Do you have a ‘white paper’ on how the daily ‘after the fact’ Crop Evapotranspiration numbers (CE) are calculated?

I think what I’m hearing, first from McKynzee, and now you, is that for identical cloud conditions (and maybe wind conditions), for say a day in July versus a day in Jan., the ‘after the fact’ CE number will be identical (no variation as a function of temperature or time of year (growing versus non-growing season)).

My conclusion is simply that the Rachio product is not as aggressive toward limiting water as I thought it was. And that making change to the CE number in spite of identical cloud cover days in Summer versus Winter, and in 95 degree F versus 40 degree temperature, is opportunity for enhancement.

And thus the Rachio product is basically a ‘follow the rain’ product with a fancy front end that results in per-zone duration values that we all used to simply set via guessing at ‘number of minutes to run’ on our old controllers.

I used to use a Rain Dial RD1200-R controller coupled to an Irritrol Climate Logic unit. This system was more crude in many respects compared to replacing it with Rachio product, using an onsite measurement unit for ambient temperature, rain and cloudiness detection (solar insolation sensor) versus now being connected to a nearby weather station. The Climate Logic unit included a flash card of seasonal weather change patterns for all over the U.S., and by specifying your ZIP, you got benefit of reduced watering in the wintertime and with cold temperature.

Rain Dial’s accomplishing with hardware what Rachio product wants to accomplish with s/w (keeping track of the soil’s current moisture balance to determine when to irrigate, and on a zone by zone basis). It’s increasingly clear now that the Rachio product isn’t (yet) where competing, h/w based products have been.

I look forward to seeing what Rachio’s continued product development brings to the table.

Best regards,