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Fixes to Energy related documentation (#18700)

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* Update faq.markdown

* fix units

* Apply suggestions from code review

Co-authored-by: Franck Nijhof <frenck@frenck.dev>

* rewriting

Co-authored-by: Franck Nijhof <frenck@frenck.dev>
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Diogo Gomes 2021-08-03 13:50:53 +01:00 committed by Franck Nijhof
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source/_docs/energy/electricity-grid.markdown
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@ -21,7 +21,7 @@ Home Assistant will need to know the amount of energy flowing through your meter
### Using a CT clamp sensor ### Using a CT clamp sensor
CT clamp sensors measure the instantaneous current passing through an electrical wire. To translate this into electrical power (Wh) you also need a voltage measurement, because Power = Current x Voltage. CT clamp sensors measure the instantaneous current passing through an electrical wire. To translate this into electrical power (W) you also need a voltage measurement, because Power = Current x Voltage.
In Home Assistant we have support for off-the-shelf CT clamp sensors and you can build your own with ESPHome's [CT Clamp Current sensor](https://esphome.io/components/sensor/ct_clamp.html). In Home Assistant we have support for off-the-shelf CT clamp sensors and you can build your own with ESPHome's [CT Clamp Current sensor](https://esphome.io/components/sensor/ct_clamp.html).

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@ -5,14 +5,24 @@ description: "Home Energy Management is a vast topic and not everything might be
## Energy vs Power ## Energy vs Power
Energy is a quantitative measurement of what it takes to produce work (e.g. heat water) while Power measures the speed at which energy is transferred. It's a common mistake to take Power as an Energy value, but the two are not alike.
Electrical Power is usually measured in Watts (W) and Electrical Energy is usually measured in Watt-Hour (Wh) (not to be confused with Watt/Hour). [Energy](https://en.wikipedia.org/wiki/Energy) is a quantitative measurement of what it takes to produce work (e.g. heat water) while [Power](https://en.wikipedia.org/wiki/Electric_power) measures the speed at which energy is transferred.
This difference is very important as you need to use the proper entities and/or convert between the two. Energy (Watt-Hour) is not an average of the Power you are consuming over a given period of time, but the sum of the power function: Power is the derivative of Energy over time. Electrical Power is measured in Watts (W) and Electrical Energy is measured in kiloWatt-hour (kWh).
Think of this in a parallel to speed and distance: Power is the speed you are going and Energy is the distance driven. Think of this in a parallel to speed and distance: Power is the speed you are going and Energy is the distance driven.
Therefore Energy (kiloWatt-hour) is not an average of the Power you are consuming over a given period of time (that would be kiloWatt/hour). Energy is the integral (mathematical operation) of the Power function.
This difference is very important as you need to use the proper entities in our Energy Panel.
## Creating an Energy Sensor out of a Power Sensor
Since in Home Assistant, we don't deal with Power functions but with samples of the power being used, we can't do the integral (mathematical operation) directly and get the true amount of energy consumed/produced.
That said, if you can sample Power values fast enough (every few seconds) you can reliably measure energy transferred through mathematic approximations called [Riemann Sum](https://en.wikipedia.org/wiki/Riemann_sum). Home Assistant provides this mathematical operation through the [integration](/integrations/integration/#energy).
## Split consumption by tariffs ## Split consumption by tariffs
If you are using a 3rd party device (e.g. not reading directly from your utility meter device or from the utility provider cloud service) you need HA to split your energy measurements into 2 (or more) tariffs, in order to track these energy consumptions separately. If you are using a 3rd party device (e.g. not reading directly from your utility meter device or from the utility provider cloud service) you need HA to split your energy measurements into 2 (or more) tariffs, in order to track these energy consumptions separately.

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@ -15,7 +15,7 @@ Home Assistant will need to know the amount of energy that is being produced. Th
### Using a CT clamp sensor ### Using a CT clamp sensor
CT clamp sensors measure the instantaneous current passing through an electrical wire. To translate this into electrical power (Wh) you also need a voltage measurement, because Power = Current x Voltage. CT clamp sensors measure the instantaneous current passing through an electrical wire. To translate this into electrical power (W) you also need a voltage measurement, because Power = Current x Voltage.
In Home Assistant we have support for off-the-shelf CT clamp sensors and you can build your own with ESPHome's [CT Clamp Current sensor](https://esphome.io/components/sensor/ct_clamp.html). In Home Assistant we have support for off-the-shelf CT clamp sensors and you can build your own with ESPHome's [CT Clamp Current sensor](https://esphome.io/components/sensor/ct_clamp.html).