Based on my observations of Flex Daily, the one variable I wonder about is ET. As I mentioned in Arizona Turf Water Consumption, the ET computed by Rachio seems a little higher than what AZMET indicates.
That said, it isn’t crazy high for me at least, and certainly not double. Aside from ET, most of the calculations Rachio does aren’t too difficult, and you can sanity check them by hand via your advanced settings:
Watering Duration
- Calculate availableWater * allowedDepletion * rootDepth. Example: 0.2 * 40% * 6.00" = 0.48". This is how many inches are needed to fill your root zone starting at the brown line on your Moisture Graph. You should see this value appearing periodically in your “Forecasted” Flex Moisture Level details.
- Divide by your precipitation rate to determine how long an ideal system would water. Example: 0.48" / 1.65"/hr = 0.29 hr.
- Multiply by 1 / (0.4 + 0.6 * efficiency) to figure out how long your system must water. This is about how long Rachio will water normally. Example: 0.29hr * (1 / (0.4 + 0.6 * 49%)) = 0.29 * 1.44 = .42 hr = 25 minutes. (I sometimes get a slightly different answer than Rachio but it’s pretty close.)
Frequency
- Temporarily set your crop coefficient to 100% and read off a daily ET value in the Moisture Graph details. This should be close to the so-called “reference ET” for your area. For Phoenix this is in AZMET summary - maybe there’s a similar site for your area.
- Multiply the reference ET by your real crop coefficient e.g. 70% - this is how many inches Rachio “wants” to water for the day due to weather.
- Once you’ve accumulated (due to weather) the number of inches from Watering Duration step #1 less any precipitation or manual waterings, Rachio will water. You can see this in your Moisture Level details.
Hope this helps you cross check what Rachio is doing. There are lots of variables so it’s hard to say what changed for you YOY without digging into details, but if you didn’t change settings then ET may be the wildcard.