Forecast.Solar provides data based on your location, the declination and orientation of your solar panels.

Solar production

(All plans)

The always weather based solar production forecast, historic averages and clear sky optimum provides watt powers and kilo watt energy data.


(Professional account)

The weather forecast provide sky coverage amount, textual weather condition and icon URL, temperature and some wind information.


(Professional account)

Draw a daily solar production forecast chart with simple Javascript snippets.

Solar production forecast and weather forecast data are provided for up to 7 days with a resolution of 1 hour down to 15 minutes.

If you then checked the documentation and you like it, register an account for more features.

Data coverage

The figure shows the areas covered by the Photovoltaic Geographical Information System (PVGIS) solar radiation databases and therefor by Forecast.Solar.

PVGIS databases

(click to enlarge)

Restful API

The API can deliver responses in JSON, CSV or XML

The Swagger compatible API definition is available in YAML.

Example: Get solar production estimate



Response (professional account, 15 minutes resolution)

    "result": {
        "watts": {
            "2019-06-22 05:15:00": 17,
            "2019-06-22 05:30:00": 22,
            "2019-06-22 05:45:00": 27,
            "2019-06-29 20:15:00": 14,
            "2019-06-29 20:30:00": 11,
            "2019-06-29 20:45:00": 7
        "watt_hours": {
            "2019-06-22 05:15:00": 0,
            "2019-06-22 05:30:00": 6,
            "2019-06-22 05:45:00": 12,
            "2019-06-29 20:15:00": 2545,
            "2019-06-29 20:30:00": 2548,
            "2019-06-29 20:45:00": 2550
        "watt_hours_day": {
            "2019-06-22": 2626,
            "2019-06-23": 2918,
            "2019-06-24": 2526,
            "2019-06-25": 2866,
            "2019-06-26": 2892,
            "2019-06-27": 1900,
            "2019-06-28": 2199,
            "2019-06-29": 2550
    "message": {
        "type": "success",
        "code": 0,
        "text": ""


You can direct draw chart for solar production estimate using the Forecast.Solar widget.

(Professional account)

Chart for the geographical midpoint of Germany at  51°9'N,10°27'E  with a declination of 37°, looking south with 10 kilo watt peak installated.


Without given title or subtitle, no title is printed and the subtitle defaults to date


Title with date placeholder, no subtitle is printed

It is also possible to show charts of the historic average data and the theoretic data for clear sky conditions.
Todays historic average production

Title without date placeholder, subtitle defaults in this case to the date

Todays theoretical clear sky production

No title given but subtitle with placeholder

Please refer to the documentation for details and check also the example page.
The Script URL was build with: https://api.forecast.solar/demo-key/chart/51.15/10.45/37/0/10

Account models

Please always test with the public API before make a subscription. Check if you get valid data for your location!
As pre-check you can test with the Photovoltaic Geographical Information System (PVGIS).
You should consider to register an account for more features, compare plans in detail.



No registration required, free for life.

Best for users without loggers to get a quick idea about coming solar production.

If you don't want to use your paid subscription after the trial period, you can cancel the subscription any time during the trial period and no costs will be charged.


12 EUR/year

(equate to 1 EUR/month)

Registration with a valid email required, access with API key, free trial of 14 days.

Provide the same features as the Public API plus:

Best for users with loggers to integrate the data automatic.

Personal Plus

24 EUR/year

(equate to 2 EUR/month)

Registration with a valid email required, access with API key, free trial of 14 days.

Provide the same features as the Personal API with more detailed data:

  • Forecast horizon: This and the next 3 days
  • Data resolution: 15 minutes
Best for users with loggers to integrate more detailed data automatic.


60 EUR/year

(equate to 5 EUR/month)

Registration with a valid email required, access with API key, free trial of 14 days.

Provide the same features as the Personal API plus:

Best for business users with more than one plant and/or loggers to integrate the data automatic.

It is not allowed to share the API key with e.g. clients of your product! (It will also not work because of the rate limits for the API key.)

If you are developing an APP that will be used by clients, the following setup is suggested:

  • Deliver the APP with the use of the Public API.
  • Give the clients the option to subscribe for an own API key if they are interested in having data more accurate.
    (This for example the way, how the Home Assistant integration works.)

If you will not share the API key and you can guarantee, that your API key is not viewable to others, please get in touch for an Enterprise account.


Registration with a valid email required, access with API key, free trial of 14 days.

Provide the same features as the Professional API, but with higher rate limits.


Home assistant is an open source home automation that puts local control and privacy first.

The integration was introduced in Home Assistant 2021.7

Solectrus is an alternative photo­voltaic dashboard that visualises the yield and consumption of a PV system.

Available on Github.

ioBroker is an open source automation IoT platform (Fog computing).

The adapter is available on Github.

The Python Package Index (PyPI) is a repository of software for the Python programming language.

Asynchronous Python client for getting forecast solar information.


KNX - the intelligent standard for building

The logic module Forecast Solar pro­vides a forecast of the PV yield of a specific site (E5 & E6).

Support channels

An Discord channel, an Issue tracker and a Forum are available for support.
Forecast your Solar production

With the increasing share of photovoltaics in the electricity market, the importance of Solar energy forecasts. These are an important tool for the integration of Solar power into existing network structures.

The production of solar power is dependent on external influences on which man has no or only limited influence. For example, Season, time of day, weather (eg ambient temperature, clouds, air turbidity).

A solar day covers the global energy supply for eight years.

Predictions about the availability of solar-generated electricity in the future support private power management, but are of great importance, above all, for commercial solar power generators and network operators.

© 2015-2021 by Knut Kohl . Consulting | v2.12-53-f0280af | Forum | Photos: Flickr