Forecast.Solar: adding inverter capacity on config page


First of all, I wanna thank the people involved in this integration.

Here is a feedback I thought it was worth sharing to the community.
My first PV install consisted of 7110 Wp of PV with an 7 kVA inverter. Last year, I added panels to my installation to go with 12000+ Wp but keeping the same inverter.

It would be nice if we could specify the size the inverter on top of how much the panels can produce on peak time, a bit like what SolCast is doing.



the Forecast.Solar API have a (yet undocumented) URL parameter for this:

?inverter=<max. power in watt>

so for your setup this would be


This will cap the forecast to max. inverter power.



Hi Knut, that’s great news! Would there currently be a way to use that parameter in Home Assistant or will we need to wait for the integration to be updated?

Must implemented in the intergration, this builds the URL.

Added it to the docu: api [Forecast.Solar]

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Ok, so I’ll patiently wait this feature to be implemented if someone has the time to do so.
Unfortunately, I wouldn’t know where to start…

Thanks for your reply !

It took a while but this feature will be available soon :smiley: What I did notice during testing, however, is that you have to send the value in kilowatts, otherwise you will not see that the max number of kWh is capped by the max inverter size that you have specified.

In the integration itself you will simply enter the number of watts, because we also use this for kWp and this prevents incorrect input by a user.

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Hello @klaasnicolaas,

Thank you, that’s great news !

Hi. I have a question regarding this integration: I have 8100 kWp modules, but a 6000 W inverter. I entered these values in the Forecast.Solar integration, but the forecast graph in the engery dashboard exeeds the 6000 W limit. Shouldn’t it be limited to the inverter’s size?
I tested the Forecast.Solar API. I tried the following:
48 is the latitude
16 is the longitude
38 is the declination in degrees
-40 is the azimuth (which is 140 degree in Home Assistant)
8.1 is my modules kWp
6 is my inverters maximum kW

The parameters are documented here: api:estimate [Forecast.Solar]
With this API call I get results for today that limit at 6kW, which is fine:
|2022-10-11 07:05:00|0|
|2022-10-11 08:00:00|3841|
|2022-10-11 09:00:00|5341|
|2022-10-11 10:00:00|6000|
|2022-10-11 11:00:00|6000|
|2022-10-11 12:00:00|6000|
|2022-10-11 13:00:00|5345|
|2022-10-11 14:00:00|4255|
|2022-10-11 15:00:00|2843|
|2022-10-11 16:00:00|1277|
|2022-10-11 17:00:00|652|
|2022-10-11 18:00:00|239|
|2022-10-11 18:14:00|0|

But the API call also returns kWh for each hour, which is this in my case:
|2022-10-11 07:05:00|0|
|2022-10-11 08:00:00|1760|
|2022-10-11 09:00:00|6351|
|2022-10-11 10:00:00|12095|
|2022-10-11 11:00:00|18429|
|2022-10-11 12:00:00|24778|
|2022-10-11 13:00:00|30538|
|2022-10-11 14:00:00|35338|
|2022-10-11 15:00:00|38887|
|2022-10-11 16:00:00|40947|
|2022-10-11 17:00:00|41912|
|2022-10-11 18:00:00|42357|
|2022-10-11 18:14:00|42385|

I think, Home Assistant uses these kWh values and calculates the kWh for each hour by substracting the values with the ones of the previous hour. And here, the inverter size is not considers. E.g. at 11:00 the kW is 6000, but the kWh for this hour is 18429 - 12095, which is 6334.

@Forecast.Solar: So, I think it is really an issue in the calculation, which is done by Forecast.Solar. Can you consider the inverter size in this calculation?

Confirmed, wrong calulation in some cases

Fixed with API version v5.55.3, so next fetch should correct the data.

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Perfect! Now it limits at the inverter’s size. Thanks!!!