Making an estimated kWh sensor | Home Assistant | Page 1

jaunty raptor Jul 30, 2025, 8:36 PM

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I have a w/sqm input and I wanted to convert that value to estimated solar production but I have no idea how.

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something like ([sun w/sqm]*[average panel efficiency% NOCT])*[total panel area]

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so 1000w sqm would equate to around 740w from the panel, 800w would be about 600w etc

wanton sonnet Jul 30, 2025, 8:44 PM

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You're looking for a PV simulator! I am working on one

jaunty raptor Jul 30, 2025, 8:46 PM

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wanton sonnet You're looking for a PV simulator! I am working on one

I wanted it to be in home assistant as a graph of how much my panels should be making

wanton sonnet Jul 30, 2025, 8:47 PM

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That's what I'm making

jaunty raptor Jul 30, 2025, 8:48 PM

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of course that math assumes that the panels are pointing directly at the sun. Right now with the formula I'm estimating to make 340w but I'm actually making 160w

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I'd have to add something like sin [sun elevation] to it

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actually that's EXACTLY what I need to do

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"(([sun w/sqm][average panel efficiency NOCT])[total panel area])sin [sun elevation]"

wanton sonnet Jul 30, 2025, 8:51 PM

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You can use a transposition model

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It's making a projection from the sun vector to the in-plane radiation vector

jaunty raptor Jul 30, 2025, 8:52 PM

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and I'm making 153w right now

jaunty raptor Jul 30, 2025, 8:53 PM

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wanton sonnet It's making a projection from the sun vector to the in-plane radiation vector

I'm gonna need help lol

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((445*11.7%)*6.65)sin 29.63

wanton sonnet Jul 30, 2025, 8:56 PM

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What type of radiation data do you have?

jaunty raptor Jul 30, 2025, 8:56 PM

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a weather station

wanton sonnet Jul 30, 2025, 8:57 PM

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I mean the type. GHI?

jaunty raptor Jul 30, 2025, 8:57 PM

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jaunty raptor `((445*11.7%)*6.65)sin 29.63`

for some reason google gave me -338?

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no idea

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it's from ambient weather

wanton sonnet Jul 30, 2025, 8:57 PM

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It's important

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Otherwise the calculation makes no sense

jaunty raptor Jul 30, 2025, 8:58 PM

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jaunty raptor `((445*11.7%)*6.65)sin 29.63`

doing it on my phone I get 171w

jaunty raptor Jul 30, 2025, 8:58 PM

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jaunty raptor and I'm making 153w right now

so there's some loss in the wire and whatnot but that's pretty damn close

wanton sonnet Jul 30, 2025, 9:02 PM

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that's only a single number. It's not a linear formula, it always involves trigonometry

jaunty raptor Jul 30, 2025, 9:23 PM

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wanton sonnet that's only a single number. It's not a linear formula, it always involves trigo...

well all it would do is graph it

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it's an estimated solar production value

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It'll go on top of this

wanton sonnet Jul 30, 2025, 9:23 PM

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what's the area of your panel?

jaunty raptor Jul 30, 2025, 9:24 PM

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total? it's in the forrmula, 6.65sqm

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it's actually a little less because of the spaces between the cells and where there's only glass/frame but it's good enough

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I just don't know how to make it into a helper

wanton sonnet Jul 30, 2025, 9:26 PM

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it's gonna be a template sensor

jaunty raptor Jul 30, 2025, 9:26 PM

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and I have to limit the sun elevation because it'll go negative

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normal or binary sensor?

wanton sonnet Jul 30, 2025, 9:27 PM

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why would it be binary

jaunty raptor Jul 30, 2025, 9:27 PM

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idk about helpers

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I guess this moved from kwh to wanting watts so I can graph it

wanton sonnet Jul 30, 2025, 11:00 PM

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you do know what binary means? 0, 1?

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anyway. If you lookup a basic transposition model (or ask AI to make one for you) you should be able to get a decently accurate power value

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You dont need panel size or efficiency, you just need panel power at 1000W/m2 irradiance

jaunty raptor Jul 31, 2025, 1:56 AM

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wanton sonnet you do know what binary means? 0, 1?

ah

jaunty raptor Jul 31, 2025, 1:56 AM

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wanton sonnet You dont need panel size or efficiency, you just need panel power at 1000W/m2 ir...

no I don't because that value is wrong

jaunty raptor Jul 31, 2025, 2:02 AM

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wanton sonnet You dont need panel size or efficiency, you just need panel power at 1000W/m2 ir...

what I could do it use the NOCT rating, not the STC rating which would give the right values

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idk how that would work though and I don't know how to write the forumula

wanton sonnet Jul 31, 2025, 7:45 AM

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No you don't need that

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But feel free to ignore my advice

jaunty raptor Jul 31, 2025, 7:58 AM

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wanton sonnet No you don't need that

I can always change it later

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I'm close though. I need help on the sine part

wanton sonnet Jul 31, 2025, 8:05 AM

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Transposition model

jaunty raptor Jul 31, 2025, 8:27 AM

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wanton sonnet Transposition model

yes but how

wanton sonnet Jul 31, 2025, 10:48 AM

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that is the how

jaunty raptor Jul 31, 2025, 11:01 AM

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?

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I have literaly no idea what you're talking about

wanton sonnet Jul 31, 2025, 11:07 AM

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have you googled what a transposition model is?

jaunty raptor Jul 31, 2025, 5:33 PM

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wanton sonnet have you googled what a transposition model is?

I mean I got this https://www.pvsyst.com/help-pvsyst7/models_meteo_transposition.htm

Physical models used > Irradiation models > Transposition model

Transposition model

wanton sonnet Jul 31, 2025, 5:46 PM

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so basically you need this

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you have G

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you need to calculate θ

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https://pvpmc.sandia.gov/modeling-guide/1-weather-design-inputs/plane-of-array-poa-irradiance/calculating-poa-irradiance/angle-of-incidence-clone/

PV Performance Modeling Collaborative (PVPMC)

Angle of Incidence

The angle of incidence ($$AOI$$) between the Sun’s rays and the PV array can be determined as: $$AOI=cos^{-1}[cosleft(theta_zright)cosleft(theta_Tright)+sinleft(theta_Zright)sinleft(theta_Tright)cosleft(theta_A-theta_{A},_{array}right)]$$ where $$theta_A$$ and $$theta_Z$$ ar...

jaunty raptor Jul 31, 2025, 5:59 PM

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wanton sonnet you need to calculate θ

I have 0 clue how to code in HA

wanton sonnet Jul 31, 2025, 6:06 PM

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good moment to learn

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you can use this as a starting point:

template:
  - sensor:
      - name: "Solar AOI"
        unit_of_measurement: "°"
        state: >
          {% set deg2rad = pi / 180 %}
          {% set rad2deg = 180 / pi %}

          {% set sun_azi = deg2rad * state_attr('sun.sun', 'azimuth') %}
          {% set sun_zen = deg2rad * (90 - state_attr('sun.sun', 'elevation')) %}
          
          {% set panel_tilt = deg2rad *  30.0 | float %} 
          {% set panel_azi = deg2rad * 180 | float %} {# 180 deg = south #}

          {% set cos_aoi =
            cos(sun_zen) * cos(panel_tilt) + sin(sun_zen) * sin(panel_tilt) * cos(sun_azi - panel_azi)
          %}

          {{ acos(cos_aoi) * rad2deg }}

jaunty raptor Jul 31, 2025, 6:30 PM

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wanton sonnet you can use this as a starting point: ```yaml template: - sensor: - nam...

what am I even looking at lol

wanton sonnet Jul 31, 2025, 6:32 PM

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jaunty raptor what am I even looking at lol

this computes the angle between the sun and your panel

wanton sonnet Jul 31, 2025, 6:32 PM

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wanton sonnet so basically you need this

theta in this image

jaunty raptor Jul 31, 2025, 6:33 PM

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ah

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also a slightly separate question, how do I limit output to 0 for a helper?

wanton sonnet Jul 31, 2025, 6:35 PM

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you cant, only for templates

jaunty raptor Jul 31, 2025, 6:35 PM

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I'm basically trying to limit solar production values so it doesn't go above another value

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so it shouldn't be negative

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I wanted to either limit the value to 0 or limit the value to the max of another value

wanton sonnet Jul 31, 2025, 6:37 PM

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you would need a template for that

jaunty raptor Jul 31, 2025, 6:37 PM

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template helper?

wanton sonnet Jul 31, 2025, 6:37 PM

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max(max(input, reference), 0)

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yes

jaunty raptor Jul 31, 2025, 6:39 PM

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template sensor or?

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I'm not sure where I need to do it

wanton sonnet Jul 31, 2025, 6:45 PM

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template sensor or template helper both are okay

jaunty raptor Jul 31, 2025, 6:49 PM

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so how would I actually use it?

wanton sonnet Jul 31, 2025, 6:50 PM

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use what?

jaunty raptor Jul 31, 2025, 6:52 PM

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the max value

jaunty raptor Jul 31, 2025, 6:56 PM

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wanton sonnet use what?

gotta remember I have 0 clue how to code things

wanton sonnet Jul 31, 2025, 6:57 PM

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it's a template, it creates a sensor

wanton sonnet Jul 31, 2025, 6:57 PM

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jaunty raptor gotta remember I have 0 clue how to code things

you can just google this

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read the documentation

jaunty raptor Jul 31, 2025, 6:58 PM

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am I even doing this right?

wanton sonnet Jul 31, 2025, 7:01 PM

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https://www.home-assistant.io/docs/configuration/templating/

Home Assistant

Templating

Instructions on how to use the templating feature of Home Assistant.

jaunty raptor Jul 31, 2025, 7:01 PM

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yeah I'm looking at it

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what's sun.sun?

wanton sonnet Jul 31, 2025, 7:07 PM

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tracking the position of the sun

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everyone has it

jaunty raptor Jul 31, 2025, 7:10 PM

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ah

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I also found this but idk if they use the model https://www.home-assistant.io/integrations/forecast_solar/

Home Assistant

Forecast.Solar

Instructions on how to integrate Forecast.Solar within Home Assistant.

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the value is matching what I have already but my actual production is lower

wanton sonnet Jul 31, 2025, 7:12 PM

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well yeah that is basically doing the same thing as the formulas

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but then you're dependent on a cloud integration

jaunty raptor Jul 31, 2025, 7:12 PM

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yeah

jaunty raptor Jul 31, 2025, 7:13 PM

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wanton sonnet https://www.home-assistant.io/docs/configuration/templating/

this doesn't really tell me how to make a template, only how to look at it in dev tools

wanton sonnet Jul 31, 2025, 7:15 PM

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https://www.home-assistant.io/integrations/template/

Home Assistant

Template

Instructions on how to integrate Template Sensors into Home Assistant.

jaunty raptor Jul 31, 2025, 7:18 PM

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so it is under helpers

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I just don't know which option it is

jaunty raptor Jul 31, 2025, 7:23 PM

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jaunty raptor am I even doing this right?

so this is right?

wanton sonnet Jul 31, 2025, 7:29 PM

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it's the right helper yeah

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template is not right

jaunty raptor Jul 31, 2025, 7:31 PM

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wanton sonnet template is not right

so not sensor?

wanton sonnet Jul 31, 2025, 7:32 PM

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I mean the code is not right

jaunty raptor Jul 31, 2025, 7:33 PM

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I just copy pasted yours

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I tried the sun one but it just yelled at me

wanton sonnet Jul 31, 2025, 7:35 PM

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yeah this is all really basic stuff

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ask the template people for help

jaunty raptor Jul 31, 2025, 7:36 PM

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basic for you maybe

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I don't even know what result I'm supposed to be getting here

wanton sonnet Jul 31, 2025, 7:41 PM

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basically this measures the angle between the sun and your panel

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so if the sun is directly on the panel it returns an angle of 0

jaunty raptor Jul 31, 2025, 7:42 PM

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shouldn't it only be a number?

wanton sonnet Jul 31, 2025, 7:42 PM

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if it is hitting it from the side the angle is 90 degrees

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yes it's a number

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idk why you typed yah

jaunty raptor Jul 31, 2025, 7:43 PM

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I was wondering wtf that was

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wait why do I need the rest of that stuff

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that's what I was looking for

wanton sonnet Jul 31, 2025, 7:44 PM

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you still have to set panel tilt and azimuth

jaunty raptor Jul 31, 2025, 7:45 PM

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yeah that's an easy fix

wanton sonnet Jul 31, 2025, 7:45 PM

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the rest of the stuff is if you configure a template sensor directly in configuration.yaml

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so you can do that, or just put this template in a template sensor helper without all the extra stuff

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just try and see what works

jaunty raptor Jul 31, 2025, 7:47 PM

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so I think I'd need cosine instead of sine for the calculation now

wanton sonnet Jul 31, 2025, 7:48 PM

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why

jaunty raptor Jul 31, 2025, 7:49 PM

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well my current watt caulation is based on the angle of the sun, so elevation at noon is 90° or thereabouts. With the new one it's 0

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when it's set elevation 0 for one and 90 for the other. they're swapped

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so now I have 3 separate values to look at.

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1 based on sun angle
2 based on your thing
3 with no elevation considered (as if the panels are always facing the sun)

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I'm seeing about 470w on the panels atm

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what a mess. really annoying the HA calculates angles in radians and not degrees

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I have to have a helper to convert rad to degree every time I need one

wanton sonnet Jul 31, 2025, 8:08 PM

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if you want to actually use mine you still need:

{% set deg2rad = pi / 180 %}

{% set sun_azi = deg2rad * state_attr('sun.sun', 'azimuth') %}
{% set sun_zen = deg2rad * (90 - state_attr('sun.sun', 'elevation')) %}
{# replace by G = states('sensor.irrads') | float #}
{% set G = 0.3 %}

{% set panel_tilt = deg2rad *  90.0 | float %} 
{% set panel_azi = deg2rad * 308.32 | float %} {# 180 deg = south #}
{% set panel_power = 300 | float %} {# watt #}

{% set cos_theta =
  cos(sun_zen) * cos(panel_tilt) + sin(sun_zen) * sin(panel_tilt) * cos(sun_azi - panel_azi)
%}

{{ G * panel_power * cos_theta }}

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this is making the assumption that all irradiation is beam irradiance. Which in reality is always false unless you have clear skies

jaunty raptor Jul 31, 2025, 8:16 PM

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wanton sonnet this is making the assumption that all irradiation is beam irradiance. Which in ...

I assume the weather station has a translucent but cloudy thing to sense light from multiple angles

wanton sonnet Jul 31, 2025, 8:17 PM

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sure but it doesnt tell you what the diffuse component is

jaunty raptor Jul 31, 2025, 8:18 PM

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yeah

jaunty raptor Jul 31, 2025, 8:18 PM

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wanton sonnet if you want to actually use mine you still need: ```yaml {% set deg2rad = pi / ...

this is reading lower than my panel meter

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I'm reading 440w and it's giving me 175

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and yes I edited it

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deg2rad is a thing?

wanton sonnet Jul 31, 2025, 8:19 PM

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you didn't set G

jaunty raptor Jul 31, 2025, 8:20 PM

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what's G?

wanton sonnet Jul 31, 2025, 8:20 PM

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the irradiance you measure

jaunty raptor Jul 31, 2025, 8:20 PM

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oh so I literally have to cut out the 0.3% and replace it with the sensor?

wanton sonnet Jul 31, 2025, 8:21 PM

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thats what I put in the comment above that line yes

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im not sure how else you could get power

jaunty raptor Jul 31, 2025, 8:22 PM

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why not type is as sensor.irradiance as a placeholder so I'm not so confused lol

wanton sonnet Jul 31, 2025, 8:22 PM

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why not read

jaunty raptor Jul 31, 2025, 8:22 PM

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I do not code

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I take everything that's just given to me as is

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I don't know what things do

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I don't know why things are there

wanton sonnet Jul 31, 2025, 8:23 PM

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so you read greyed out replace by ... and you think that's code?

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interesting

jaunty raptor Jul 31, 2025, 8:24 PM

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wanton sonnet Jul 31, 2025, 8:26 PM

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something is not symmetric!

jaunty raptor Jul 31, 2025, 8:27 PM

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wanton sonnet Jul 31, 2025, 8:27 PM

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yeah, its on the line you selected

jaunty raptor Jul 31, 2025, 8:28 PM

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I don't know

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doesn't work with it, doesn't work without it

wanton sonnet Jul 31, 2025, 8:36 PM

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check carefully what you're missing

jaunty raptor Jul 31, 2025, 9:20 PM

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wanton sonnet check carefully what you're missing

I got nothing

wanton sonnet Jul 31, 2025, 9:20 PM

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sad

jaunty raptor Jul 31, 2025, 9:21 PM

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idk what to tell you

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I said before, if it's there it doesn't like it, if it's not there it doesn't like it

wanton sonnet Jul 31, 2025, 9:22 PM

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jaunty raptor Jul 31, 2025, 9:34 PM

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wanton sonnet

yeah it returns some ridiculous number

wanton sonnet Jul 31, 2025, 9:35 PM

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divide panel power by 1000

jaunty raptor Jul 31, 2025, 9:39 PM

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there, more clear

wanton sonnet Jul 31, 2025, 9:41 PM

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it depends on what unit your irradiance sensor is, I had no way of knowing

jaunty raptor Jul 31, 2025, 9:41 PM

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ah

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it's in watts

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is there a way to round that to the nearest watt?

wanton sonnet Jul 31, 2025, 9:42 PM

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| round(0)

jaunty raptor Jul 31, 2025, 9:45 PM

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wanton sonnet Jul 31, 2025, 9:50 PM

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probably wanna set device class : power

jaunty raptor Jul 31, 2025, 9:53 PM

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wanton sonnet probably wanna set device class : power

still didn't work

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but yeah I probably should anyway

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also this only updated every 4 minutes

wanton sonnet Jul 31, 2025, 9:55 PM

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it will update whenever one of the inputs updates

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so for sun platform thats once every few minutes, but your irradiance sensor is probably faster

jaunty raptor Jul 31, 2025, 9:56 PM

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ah

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you get the elevation and azimuth from sun.sun?

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actually I was going to say why not use the sun integration but that updates every 4 minutes too

wanton sonnet Jul 31, 2025, 9:59 PM

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this is using sun integration

jaunty raptor Jul 31, 2025, 10:01 PM

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oh duh. I guess I never noticed the stepping before

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it was obvious here but now that I blew it up I see it on the other graphs too

wanton sonnet Jul 31, 2025, 10:03 PM

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im a bit red-green color blind so that graph doesnt make any sense to me lol

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pick colors that are further apart

jaunty raptor Jul 31, 2025, 10:03 PM

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woops

wanton sonnet Jul 31, 2025, 10:03 PM

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what do you mean by stepping?

jaunty raptor Jul 31, 2025, 10:04 PM

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stepping like stairs

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or did I just get closer

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oh wait no blue's further

wanton sonnet Jul 31, 2025, 10:07 PM

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jaunty raptor Jul 31, 2025, 10:09 PM

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now that's harder for me to see

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it's dark blue on black

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so that finally works as intended! and I got the 0w limiter working too

jaunty raptor Jul 31, 2025, 10:20 PM

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jaunty raptor so that finally works as intended! and I got the 0w limiter working too

well except for it not rounding

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how can I convert the sun irradiance to rad without a helper? {{ ((((states("sensor.irradiance_local") | float) * 0.117) * 6.65) * (states("sensor.sun_elevation") | sin)) | round }}

wanton sonnet Jul 31, 2025, 10:26 PM

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what do you mean irradiance to rad?

jaunty raptor Jul 31, 2025, 10:43 PM

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degrees to radians

jaunty raptor Jul 31, 2025, 10:44 PM

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wanton sonnet what do you mean irradiance to rad?

typed the other sensor wrong lol

wanton sonnet Jul 31, 2025, 10:45 PM

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uhh

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irradiance and radians are totally unrelated just to make sure

jaunty raptor Jul 31, 2025, 11:13 PM

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wanton sonnet irradiance and radians are totally unrelated just to make sure

yeah I didn't meant it to be that, I meant it to be sensor.sun_elevation

#Making an estimated kWh sensor