[APP][Pro] Solar Forecasts (SolCast + Forecast.Solar)

Solar Forecasts

Homey app using the Solcast API or Forecast.Solar to get solar forecasts customized for your location and installation

You can download the app here: Solcast


You could use the app to switch on electric appliances or charge a car or battery based on the forecast solar power, to maximize self-consumption.
You can compare the daily forecast with your actual production.

Solcast Setup

Sign up your solar installation at Solcast Toolkit
You have to setup the ‘Free’ Home PV owner account (hobbyist) which gives you (currently) 50 API calls a day.
Fill in all the exact details of your solar installation.

Setup the Solcast app

You have to provide your API-key and Resource ID to get the app working.
API Key can be found under - Your name - Your API key
Resource ID can be found if you click on your location on the main screen.

API Calls

  • Old users have 50 API calls/day
  • New users have 10 API calls/day

You can have 2 Solar installations in 1 account, but each update is 1 API call/each installation.

You can setup a flow to trigger a notification when the

API Fetch

Since all the automatic polling is removed, you have to set up flows to trigger an update of the values.
You can choose the intervals yourself. See examples in the second post.

  • ‘Fetch Midnight’ : This updates the Today and Tomorrow values
    (according Solcast the API calls reset at UTC, in my personal experience it is UTC+4 = 02.00LT CEST)
  • ‘Fetch update’: This updates all the values except Today.
    After this update, the app will update the values every 30 minutes (during daylight), based on the last retrieved data.
  • You can click the button to fetch an update

Forecast.Solar setup

Forecast.Solar doesn’t need an API key.
You can do maximum 12 API calls for each running hour. Extra requests are also counted as API calls.
You can add multiple installations (or different orientations)

To setup you need the enter the following details during pairing:

  • kWp of solar installation (use . for decimals) example: 6.2
  • Tilt of solar installation (0 = flat) example: 35
  • Orientation of solar installation (0 = south, -90 = east) example SE installation: -45

Advanced settings: you can change the damping factor for efficiency or performance loss. (default = 1)

Support topic

For support please use the official support topic on the forum.


If you appreciate the app: Buy me a Beer]
@athom a Homey Pro is always appreciated :slight_smile:



  • Initial release


  • Added support for upload

v 3.0.0

  • Added support for manual fetch + new api


  • Remove automatic polling
  • Remove Upload function (Solcast stopped with the function)
  • Remove automatic update when the app starts.
  • Calculating values in between API Calls
  • Add API counter + API error + timeline of updates
  • Streamlining
  • Add a button to fetch an update


  • Add Forecast.Solar
  • Add dampening factor for Forecast.Solar

**Flows for fetching updates:



Midnight update

Cool and cool app. BTW you can replace the “after sunrise” and “before sunset” conditions with “it is day” (het is overdag).


1 Like

The app is now in the app store


How do you use the information in the end, apart from uploading to SolCast and better their predictions? I’ve intrested in getting ideas on how to set charge levels of my ESS battery system depending on what predicted solar levels there is for next day. But when looking into the flows that I can enable it only seems to be forecast now is greated than or less than … The forecast now I assume is the next hour? Not the next day? Since I’m looking for ways to charge the ESS battery bank from grid during nighttime when the forecast says low sun probability for the next day.


The app will get following data:
At midnight:

  • total forecasted production today
  • total forecasted production next day

Every half hour

  • solar power now (W)
  • cumulated solar power next hour
  • cumulated solar power next 2 hours
  • cumulated solar power next 3 hours

I use the app to charge my Solaredge battery at night (during off-peak hours) when not enough solar is forecasted.

You can use the half hour predictions to start for example a washing machine, dryer, … if you know that it will consume for example 2KW during 2 hours, you could match this with the Solcast forecast

The app has limited flows built-in, but by using logic, you can do everything.

Example flow to charge battery (dutch)

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Thanks found it

Works great :grinning:
Sadly Solcast recenlty discontinued tuning the prediction model with your own production values, for accurency validation it’s still working.

Is it possible to exclude the power valueu in the energy tab in the homey app?
Couting the prediction as usage, effect’s the total use in the energy app.

Ah I didn’t know that.
That’s a bummer.

I can change that it doesn’t show up at the energy tab. I will check this week.

I can also implement https://forecast.solar/

I will check if I need to make a new app or integrate it into the same app, as a different device.

1 Like

Okay thanks!

Perhaps forecast is a better option, because the Homey Solcast app uses more than 50 updates for me, at the end of the day the API requests are consumed and the homey device is unreachable.

The free forecasts option is less accurate, as the location and pv system is less accurate.
I use it on home assistant to compare.
But I will try to implement it in the future.

It is strange that your api calls are used.
The app only polls every half hour between sunrise and sunset + 1 time at midnight.
So it should be maximum 49 calls.

Where do you live and when are the api calls used?

I just checked and the pv tuning still works, they already promise for long time to stop it.

I live in The Netherlands, only the Solcast app is connected and using api calls.
Flow’s are like u suggested, only changed the condition for sending measurements.
Seems like I only have a few api calls short.

Maybe existing tuning will be kept and new users won’t get any more?
This is what I read yesterday:

For me it look’s like this:

Ah that looks different, mine is still tuning.
Can you check how many api calls are made every day?
I live in Belgium and I have now 35 calls.
Is your location set in Homey?

Sinds today 18:21 49 calls were made.
When I check the updates at insights, there is an update every 30 minutes sinds 06:20 this morning. Should be 24+1 calls from midnight.

Looks like the api calls are double? I changed my
api key to be sure. Let see what’s happening tomorrow.

Yes my location is set in Homey.

EDIT: Problem is solved after changing API Key.

Ok great!

Next version will also keep track of the API requests.
I am just waiting for Athom to fix the issues with fw 7.1.3, as the updated app doesn’t work properly due to their bugs…

Is there a problem with refreshing the prediction values of today and tomorrow. Last refresh for me was 2 days ago…

Is all the rest refreshing?
Strange, try a reboot.
Is your location of homey set correctly?

Otherwise send me a diagnostic report

Strange… today all values were refreshed…

Thanx for your reaction


Has there been any work in regards to the idea about implementing Forecast.solar aswell? I’ve looked a bit at how Home Assistant has implemented Forecast.solar and it seems that one can, in their energy setup, define multiple PV panels in different direction and get a total estimate which would be nice for us that are running panels in different directions.