Forecast solar is way off

[Frankyie]

Hi All,

I am trying to write some code on how to decide when to charge my boiler. For this I would like to use solar forecast data from forecast.solar. However, it does not predict things that well.

Off course I set the

• Declination in forecast.solar (51 degrees)
• Azimut in forecast.solar (245 degrees)
• Total Watt peak in forecast.solar (4455W)
• Inverter size in forecast.solar (3254W)
• My home location in home assistant, zones

For your information, my house is somewhere in the middle of the Netherlands

Is this normal?

[Frankyie]

Edit:
That was not the best graph.
Here is a better one.

[koying (Chris B)]

Your predictions are actually more precise than the ones I manage to get

[Frankyie]

O dear. That’s not good
To be honest, you should not look at a single day. Every now and then there is a day where the prediction is way off. It is not always clear where the edge of big clouds are going to be.

[koying (Chris B)]

I just think their forecasts are not good.
Tbh, the only weather provider giving me decent forecasts is my country-specific one

[Biscuit (Geoff)]

@Frankyie

Is this normal?

It certainly is for myself.

https://community.home-assistant.io/t/getting-data-from-solar-forecasts/497286/8?u=biscuit

[Gav_in]

There are threads on the forum for alternative solar forecast Integrations…have a search for Solcast and/or OpenMeteo Solar and you’ll get the details…

Solcast…a lot to read in here (start from BJReplay repository posts since May 24)

Solcast Global Solar Power Forecast Integration

The BJReplay repository at GitHub - BJReplay/ha-solcast-solar: Solcast Integration for Home Assistant is currently awaiting a HACS pull request review before it can be included in the searchable integrations. Until that time, all fixes and enhancements will be released as a beta version. The current ‘latest’ release there is v4.0.31, with a ‘beta’ v4.0.34 under active community test. v4.0.35 is carrying an enhancement, and that shoud not be too far away. Open PRs. So turn on the ‘beta’ releas…

There’s also a REST sensor config in this thread for Solcast data

OpenMeteo Solar

Open-Meteo Solar Forecast

This project is based on the Forecast.Solar integration but makes use of the Open-Meteo API to generate the forecasts. The integration could be installed from GitHub - rany2/ha-open-meteo-solar-forecast: Home Assistant Open-Meteo Solar Forecast Integration. You could install it via HACS by adding it as a “Custom repository” or manually. For me, the results are better than Forecast.Solar (at least their Free tier) and on-par (if not slightly better) than Solcast. Of course, the primary advantage…

[Frankyie]

Thanks. I will look into these topics.

@Biscuit
That is beautiful data! Nice work

[Frankyie]

Perhaps good to mentions how does turned out.
I am using Solcast now. It is so much better than forecast solar. Here are some examples.

Easy day

More difficult day with clouds every now and then.

[misenko]

What I’m doing wrong ? Using solcast and it’s totally wrong. Yesterday today prediction of 25kWh but it was totally clouded here yesterday and today. Even local forecast predicted totally bad weather. No sun. Forecast solar is giving 17.8kW but no way as it’s totally clouded.

Why those huge differences ?