Help regarding choosing best Rooftop PV forecasting tool

sam_rajp1in

Hey everyone — looking for some real-world input from fellow US solar owners.

I’m based in Springfield and running a modest residential rooftop solar and storage setup. My system specs are as follows -

• 3.6 kWp PV array (REC Alpha panels)
• Sol-Ark 8K hybrid inverter
• 10 kWh Enphase IQ Battery for home backup

Overall, I’m happy with the hardware performance. The system is stable, and the hybrid plus storage combo works well for backup and peak load shifting.

Where I’m running into frustration is forecasting and planning.

For monitoring, I’m using Enphase Enlighten - the manufacturer's default dashboard. It handles system visibility fine, but when it comes to proper forward-looking Solar Production forecasting, it feels limited.

For a hybrid system, especially in a state like Illinois where weather swings can be dramatic, day-ahead forecasting is critical for my smart battery decisions.

Over the past month, I’ve tested several free/low-cost Solar Forecast tools to see how they perform for US-based systems. The candidates are the aged hot favorites, like Solcast, Forecast Solar, Meteosource, and a new kid on the block, Solar-Forecast.com.

In my experience, Solcast is probably the most consistent and “professional” feeling forecast. Forecast-Solar is not easy to use (unless you are techy), but accuracy has been hit-or-miss for my specific roof orientation and local cloud patterns.

For Meteosource, so far, it looks structured and data-heavy, but I’m still evaluating how it compares to Solcast in day-ahead accuracy. Solar-Forecast,com uses AI/ML personalization here, which is interesting for me, and it adapts based on historical performance. Some days it’s good… but I’m still judging consistency over time.

My Questions are -

1. What forecasting tools are you using for day-ahead production?
2. Has anyone done long-term accuracy comparisons (3–6 months or more)?
3. Are there better US-focused data sources I should look at?
4. Anyone integrating forecasts into Home Assistant or custom automation workflows?

QrizB

Welcome to the forum!

Hey everyone — looking for some real-world input from fellow US solar owners.

You might not have noticed but this is a UK-focused forum (yes, the sun does shine here sometimes) and I'm not aware of there being any US solar owners who post here regularly, if at all.

I have used Solcast in the past but mostly I just leave it to chance. The sun shines when it chooses to.

sam_rajp1in

https://forums.moneysavingexpert.com/discussion/comment/81883875#Comment_81883875

My bad - extremely sorry, I overlooked that. Still, if you have insights for me, please let me know.

Krakkkers

Can't you ask Professor Frink?

glennevis

PVGIS.COM provides information on solar radiation and photovoltaic system performance for any location in the world except the North and South Poles.

https://pvgis.com/

NedS

https://forums.moneysavingexpert.com/discussion/comment/81883997#Comment_81883997

Whilst PVGIS is a great tool for predicting monthly or annual irradiation totals, the OP wanted day to day forecasting of solar to manage their system - i.e, how sunny will it be tomorrow, how much solar will I generate tomorrow, that they can plug into their home automation setup.

Some solar systems (such as Tesla) integrate this feature already. For example, a Powerwall uses it's internet connection to retrieve a day ahead weather forecast, and will vary it's overnight cheap rate charging depending on how much solar it predicts will be available the next day.

I just tend to look at the weather forecast for tomorrow, and hope for the best, but I'm not trying to integrate into an automated system. I guess it becomes a lot more critical in markets where there is a large price differential between grid and solar, and/or there is no export market so use or storage of solar is more critical, hence the need to manage battery SoC.