AC limit confusion for 2-strings setup

[michal-bartak]

Hello,
I tried hard to find answers to this question, but I haven’t found anything definitive.

TLDR: Is using AC limit a realistic use case for households?

Detailed description
I have two strings, 5 kWp and 4 kWp, connected to a single 10 kW inverter.
My export to the grid is limited to 4.5 kW due to legal constraints.

As far as I’ve noticed, using AC limit caps the forecasted energy. Roughly, if AC limit is 4.5kW, then the forecast is capped to 4.5kWh.
However, my system can utilize more than 4.5 kW from PV. For example, a battery might be charging, or a washing machine might be running, and an excess of PV power might be loaded to the grid (up to 4.5kW). Given that, PV may generate up to the inverter/PV capacity.

Based on this scenario, capping might lead to underestimate forecasted energy. I think it would be better not to cap the forecast.
On the other hand, using no AC limit may result in unrealistic injection expectations. I can imagine for some it might be more important than for others.

What do you think about my thoughts? Are they valid?
How do you guys approach it (Especially in the case of regular households)

With regards

[BJReplay]

No. Don't use AC Limit in the Solcast website configuration.

You just need to look futher down the configuration screen in the Home Assistant Solcast integration for the Site Export Limit

[michal-bartak]

thank you for the prompt reaction.

by writing AC cap I meant setting in the integration. In solcast I have 10kW set for both strings.

though, the graph shows capping, see image

[autoSteve]

I can only assume that this is in the context of automated dampening, @michal-bartak.

If you have two strings and an inverter that does up to 10kW, then the Solcast site max is 10kW AC. For over-sized installs there is the 'hard limit' in the HA integration. Yours is not over-sized, where panel capacity exceeds that of the inverter. Don't set a hard limit.

If not in that context, then the sites are added to achieve the forecast, and that is largely informed by the DC capacbility. AC is just a cap because inverter, but yours is 10kW.

[michal-bartak]

Actually, it was a result of the "Inverter hard limit" settings. I've reset it to the max value.

Thank you for the clarification. Indeed, the documentation mentions that:

There is an option to set a "hard limit" for projected inverter output, and this limit will 'clip' the Solcast forecasts to a maximum value.

Though I had improperly understood "inverter output" as "output to the grid". While it's meant as the overall output.

Thank you for the support and for making this integration available to us.
Michal.

[BJReplay]

Sorry, I misunderstood, but you ended up with the right result in the end.

Gotta read the readme...

It does, pretty clearly say that the hard limit is probably not for you and almost no installations need it.

@autoSteve maybe time to deprecate it to advanced options?