Statistics max_age and sampling_size

Configuration
1

I’m trying to build a sensor that will report the max power value from an esphome connected outlet over the past 24 hours.

I started with this:

- platform: statistics
  name: "MasterTub Power Max"
  entity_id: sensor.mastertub_power
  state_characteristic: value_max
  max_age:
    hours: 24

Unfortunately, it did not hold the 24 hour max value of the sensor.mastertub_power. For some reason it was well under 24 hours. In the statistics documentation it says:

sampling_size integer (optional, default: 20)
Maximum number of source sensor measurements stored. Be sure to choose a reasonably high number if the limit should be driven by max_age instead.

So I added, “sampling_size: 240” to the sensor. I have no idea what the sampling_size is in relation to time. I was assuming that it might be related to max_age, so I set it to sample 10 times an hour. This is what it looked like today:

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So the power spike (caused by the jets being cleaned) started at 3:00 PM the previous day, but then the statistics sensor tossed this max value at around 7:30 AM the next day, obviously well inside a 24 hour window.

Am I wrong in thinking that finding a max and min over a set time period is unnecessarily convoluted here? In any case, it doesn’t work right, and no reading of the statistics documentation clears this up for me.

2

How often does your sensor update?

i.e. how may times an hour?

Multiply that by 24, that is the minimum number of sample you need for a 24 hour period.

There is an attribute of the statistics sensor called buffer_usage_ratio. You want this to be close to 1 without ever reaching 1. If it reaches 1 you need to keep more samples.

3

I don’t have a clue how many times an hour it updates. Any easy way to find that, or should I just stab around increasing the sampling_size until it works?

4

Look at the history graph for a short period of time. You should then be able to see the update interval if it is polled, or take a stab at estimating it and use the buffer fill attribute to adjust up or down.

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