The Forecast.Solar service provides solar production forecasting for your solar panel system, based on historic averages combined with weather forecasting.

This integration provides an estimated forecast on how much energy your solar panels are going to produce, allowing you to plan ahead on how you spend your produced energy most efficiently.

As an example automation idea, you could determine if:

  • You are going to produce enough solar power energy for the washing machine to run the next hour.
  • You have an electric vehicle: to determine if you will produce enough solar energy tomorrow to charge your vehicle; or if not, charge it (partly) overnight at low tariffs instead.


Forecast.Solar relies on data provided by the EU Photovoltaic geographical information system and your solar panels must be in a location that is covered by this tool. Data is available for almost the entire world.

To use the Forecast.Solar integration, it will need some information about your solar panel system: latitude, longitude, declination, azimuth and total modules power.

It needs the specific location (defined by latitude and longitude), which by default is taken from your Home Assistant configured “home” location.

The declination angle (tilt) of your solar planes (in degrees); Is the angle between your solar panels and the earth’s surface. A value of 0 means they horizontal and flat on the earth’s surface, while a value of 90 means your panels are standing up vertically.

The azimuth (in degrees on a 360° scale); Is the direction in which the front surface of your solar panels are facing towards. As a full circle is 360°, a value of 0 is facing North, 90 East, 180 South and 270 is facing West (or any value in between).

The total modules power (in Watt peak); Each solar panel, in a solar panel system, has a maximum power peak production value. In order to deliver matching estimations for you system, Forecast.Solar needs to be aware of the total maximum peak power your system can produce. Add up the maximum peak power (in Watts!) of all your panels for this value.


To add the Forecast.Solar integration to your Home Assistant instance, use this My button:

If you have more than one plane of solar modules with different properties (e.g. several sides of the roof on different strings or on different buildings, with different directions or declinations) you can add the integration multiple times setting parameters accordingly. You can then use template sensors to combine the data, e.g. adding up production on different planes into one value to base your planning on.


The Forecast.Solar integration mainly provides sensors that you can use in your automations.

  • Estimated Energy Production - Today (in kWh)
  • Estimated Energy Production - Remaining Today (in kWh)
  • Estimated Energy Production - Tomorrow (in kWh)
  • Estimated Energy Production - This Hour (in kWh)
  • Estimated Energy Production - Next Hour (in kWh)
  • Estimated Power Production - Now (in Watt)

It also provides sensors that will tell you at which date & time your peak production will be (for today and tomorrow):

  • Highest Power Peak Time - Today
  • Highest Power Peak Time - Tomorrow

There are some additionally, less common sensors, that are disabled by default. Enable those entities in the user interface if you like to use these:

  • Estimated Power Production - Next Hour (in Watt)
  • Estimated Power Production - Next 12 Hours (in Watt)
  • Estimated Power Production - Next 24 Hours (in Watt)

Using your Forecast.Solar account

The Forecast.Solar public plan can be used for free, but the resolution of the data used is more limited and thus, there are less details for this integration to work with.

If you like the Forecast.Solar service, or are interested in more frequent data updates (based on a higher data resolution), you could sign up for one of their plans.

To enable the use of the API key with this integration, go to Devices & Services. Select the Forecast.Solar integration, then select Configure. Enter the API key for your account.

Tweaking the estimations

The estimation can be tweaked and tuned to match your solar setup better. There are many factors that can cause the estimations to be slightly off (but don’t forget, it will always remain a forecast based on, e.g., weather and historical data - not actual power produced).

Luckily, there are controls to make them more accurate for your situation, for example, by slightly adjusting the azimuth or declination. If your panels catch a bit of shadow in the morning/evening, you could consider damping the results a bit.

The damping factor allows you to adjust and “damp” the results of your solar predictions in the morning and evening a bit and is a great method to make results less optimistic and more tuned to your reality. More details on damping can be found here.

The inverter size can be used in a situation where the maximum power of your inverter is lower than the total power of all your solar panels (as entered under “total modules power”) together. As a result, the forecast takes into account that the maximum solar power cannot exceed what your inverter can handle, giving you a more realistic forecast graph.

Read more about the damping factor in the Forecast.Solar documentation.

To adjust the configuration settings for your Forecast.Solar integration instance:

  1. Browse to your Home Assistant instance.
  2. Go to Settings > Devices & Services.
  3. If multiple instances of Forecast.Solar are configured, choose the instance you want to configure.
  4. Select Configure.