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How to shed light on your energy needs with the OpenWeather Solar Radiation API Historical data

How to shed light on your energy needs with the OpenWeather Solar Radiation API Historical data

Posted on 27 Jan 2022

The photons released by the sun, despite their 93 million mile journey, can provide enough light energy in a day to feed our global energy needs for a year. The solar cells that capture these photons are being developed for a wide range of applications and situations, including cost effective and lightweight cells that can be easily integrated into the structure of buildings.

Calculating the solar array size and storage needed to supply sufficient energy to a home, business or large solar array relies on understanding the historic level of solar energy available at the particular location. 

The OpenWeather Solar Radiation Current and Forecast API Historical data gives solar radiation information for up to 16 days ahead, for any location on the globe. In addition to this, we have also developed our Solar Radiation API Historical data, that can give historic solar radiation values with a 1-hour step from 1st January 1979. 

There are three indices that are returned by this easy-to-use API:

  • Global Horizontal Irradiance (GHI)
  • Direct Normal Irradiance (DNI)
  • Diffuse Horizontal Irradiance (DHI)

This OpenWeather API returns historical solar radiation data for both our clear sky and cloudy sky models. 

Our two models use enriched input data sets to build upon the Solis algorithm for clear sky, and DirInt for cloudy to give accurate results. There is a detailed description of these APIs in our documentation here.     

After gaining access, you can start retrieving data by calling the APIs:

Make an API call, using: 

  • geographic coordinates (latitude and longitude)
  • start and end date of desired historical period in the Unix format
  • Your API key

An example of the request is below:

http://api.openweathermap.org/data/2.5/solar_radiation/history?lat=51.5098&lon=-0.1180&start=1634342400&end=1634428800appid={API key}

The API response will return that solar radiation data for the specified geographical point and time period. The API response will contain DNI, DHI, GHI indices for both clear sky and cloudy sky models. 

An example of the response is below:


  "coord": {

    "lon": -114.6244,

    "lat": 32.7243


  "list": [


      "radiation": {

        "ghi": 206.68,

        "dni": 2.27,

        "dhi": 204.83,

        "ghi_cs": 826.71,

        "dni_cs": 885.47,

        "dhi_cs": 114.93


      "dt": 1618232400



Ordering the OpenWeather API cannot be easier - please contact our sales team who can explain how you can gain access for your API key. If you do not have an API key already, please just sign up here. You can also start studying our detailed technical documentation.

Let OpenWeather help you plan for a bright and sustainable future.

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