I have both Solcast and Forecast.Solar integrations installed. When I put either as my solar forecast on the Energy Dashboard I can see forecasts for days in advance.
Where can I find the data for these forecasts? All I see is entities sensor.power_production_next_24hours and sensor.solcast_forecast_tomorrow respectively.
this is, what i get with forecast solar:
entities:
Exactly- nothing beyond the next day whereas on the energy dashboard it goes several days beyond that
Not here, I can only see today and tomorrow, then it’s over…
WIth Forecast.Solar you only get today and tomorrow for free. You can have a subscription to get future data (https://forecast.solar/). You can enter an API key (optional) in the HA Forecast.Solar config.
I setup both solar forecast integrations to get a bit of redundancy and entered exactly the same system information into both. However the daily forecast can be significantly different, today for example Solcast gives 7.8 and forecast.solar gives 4.5. For me the Solcast value is more accurate.
Just wondering if anyone else having the same type of issue? My next step is to keep adjusting the system values until it matches.
Currently running a test on both side by side.
On the left - Forecast.Solar
On the right - Solcast
Both graphs are for yesterday, today, and tomorrow, both are sized to the same scale, both use the same system settings (although forecast.solar is using an applied horizon and I have to apply my own shading adjustment to Solcast). Both data sets come from my own API calls, forecast solar is run every hour (with hourly data points), Solcast I run (two planes) once for back estimates and then four times during the day for forecasts (with half-hourly data points).
It is high summer here in the UK, and for the past couple of weeks I am seeing the actual generated each day at about 90% of the forecast for Solcast.
I have been running with the forecast.solar integration for over two years, and have analysed the forecast to actual match for the past 12 months.
If anyone is interested, this is my summary analysis, for the year 21 June 2023 to 21 June 2024.
Comparing actual generated energy with the daily forecast (forecast value captured before sunrise as an average during 01:00 to 05:00)
Now plotting the ratio of actual/forecast, with ‘tolerance’ bands of 75% and 125%. As you can see, forecast over-estimates during the winter (I get about half of the forecast) and under-estimates during the summer (I get 1.5 to 2 times the forecast)
And finally, to answer the question “how much more actual do I get each day above the forecast?”
‘0’ is forecast is spot on. In practical terms, to be able to realistically use a solar forecast for home energy control, I was hoping for something within +/- 5 kWh consistently across the year, certainly in the summer when my peak production is close to 25 kWh on a good day, and perhaps +/- 2 kWh in the winter when my peak production is only 3-4 kWh per day.
A fascinating subject, hours and hours of work over years, and I am still no closer to getting a forecast figure I feel confident in using!
Edit.
I really should add that I have two planes, facing East-North-East and West-South-West, and on a single storey garage. Winter horizon shading is an issue, so I accept a reduction of 1 to 2 kWh during the morning between mid October and mid February on a typical 5-8 kWh day due to the low sun path, although I also get some compensation from light reflected back from the upper-storey house wall. All in all, difficult to set up and compensate for.
Thanks so much for all this info. I live off grid and the difference to our daily life of +/- 2kWh can be significant so having the forecasts vary by 3kWh is unhelpful.
I have ended up writing a template that uses an average of the forecasts during the morning. I also have a calculation based on current yield and daytime remaining to calculate my own version of a forecast for the afternoon.
Then as the day progresses the template uses the average of the values, eliminating the ones that are most different from reality until during the later afternoon it just uses the calculation based on my own solar input.
