# Calculate kWh
**URL:** https://discuss.elastic.co/t/calculate-kwh/188419
**Category:** Kibana
**Created:** [July 1, 2019, 10:58pm UTC](https://discuss.elastic.co/t/calculate-kwh/188419 "2019-07-01T22:58:39Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@livio.zanol](https://discuss.elastic.co/u/livio.zanol)
#### Post date: [July 1, 2019, 10:58pm UTC](https://discuss.elastic.co/t/calculate-kwh/188419/1 "2019-07-01T22:58:39Z")
Good day/night everyone! I'm new to ELK stack, and was able to make a lot of visualizations that I needed, but I'm having some trouble creating this specific Metric vusualization. Can anybody help me?
* * *
TL;DR:
Having the measure in Watts every 5 seconds from 3 different sensors pushed to Kibana, I need to create these 3 Metrics visualization:
1. Current selected period kWh (kilo watts per hour);
2. Last month kWh;
3. Current mont KWh.
* * *
Below are the values pushed to Elastic Search by Logstash every ~ 5 seconds, which are from 3 different sensors:
**val.ap\_pw** is a number in Watts that I want to make the calculation.
||Time|@timestamp|sensor|val.raw| **val.ap\_pw** |val.irms|
||Jul 1, 2019 @ 19:31:36.445|Jul 1, 2019 @ 19:31:36.445|en\_sensor2|508| **129,11** |1,02|
||Jul 1, 2019 @ 19:31:35.426|Jul 1, 2019 @ 19:31:35.426|en\_sensor1|521| **345,15** |2,72|
||Jul 1, 2019 @ 19:31:30.359|Jul 1, 2019 @ 19:31:30.359|en\_sensor3|506| **84,37** |0,66|
||Jul 1, 2019 @ 19:31:29.341|Jul 1, 2019 @ 19:31:29.341|en\_sensor2|501| **122,36** |0,96|
||Jul 1, 2019 @ 19:31:28.323|Jul 1, 2019 @ 19:31:28.323|en\_sensor1|522| **344,54** |2,71|
So, using pure math, to calculate kWh for any given time period I need to do the following:
- Calculate arithmetic mean (Average) for the individual sensors for the selected period (Let's call them M1 to M3)
- Sum the means (Let's call it Msum = M1 + M2 + M3)
- Subtract initial date from final date in the selected period (Tdifference = Tfinal - Tinitial (presuming the result will be timestamp in seconds))
- Calculate the hours in the current period (Thours = Tdifference \* 60 \* 60)
- Multiply the hours in the currently by the Sum of the means (Wh = Msum \* Thours)
- Divide by 1000 to have kWh (kWh = Wh / 1.000)
Or: **kWh = (M1 + M2 + M3) \* (Tfinal - Tinitial) /60 /60 / 1000**
Reading other questions related (like 'calculate bytes per second'), I've created this Metric below using Visual Builder, but is not showing the right value:
Actual usage:
As can be see, the result should have been something around 0,55 kWh
Can somebody help me on this? Thanks in advance.
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### Author:  [@livio.zanol](https://discuss.elastic.co/u/livio.zanol)
#### Post date: [July 2, 2019, 2:23pm UTC](https://discuss.elastic.co/t/calculate-kwh/188419/2 "2019-07-02T14:23:02Z")
Managed to do similar calculations using this math function:
_params.ap\_pw \* (last(params.\_all.ap\_pw.timestamps)-first(params.\_all.ap\_pw.timestamps)) / 60 / 60 / 1000 / 1000_, but I still have 2 problems:
1. The Avarage calculation _excludes_ missing values, but the initial/final timestamp doesn't, which will give wrong kWh results when you have missing values on the dataset.
2. I couldn't agreggate the 3 values to generate only one kWh value.
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [July 30, 2019, 2:23pm UTC](https://discuss.elastic.co/t/calculate-kwh/188419/3 "2019-07-30T14:23:03Z")
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