Curtailed output

I have a pvoutput pulling data from Solaredge cloud, and is working fine. I have a 10kw inverter but a 5kw export limit. I would like to keep track of the data that is used that would otherwise be curtailed, is whenever we are using more than 5kw of data and pv system is therefore generating that extra output, is there any way currently to get that amount, and if not, is it something that could be added in the future?

Hi @dmaunder. I read and reread your question several times and it’s a bit confusing. Are you simply trying to record WHEN your inverter is being limited to ensure that your do not exceed the 5kW limit?

How can you tell the difference between when the inverter is being limited or when the generation is simply reduced?

E.G. If the inverter is generating 8kW is it because you are consuming 3kW and exporting 5kW OR there is only enough sunlight to generate 8kW at that particular moment in time?


Hi grannos

No, I am wanting to know how much generation is being curtailed, and therefore lost. The export limit is set to 5KW, but if for instance it is actually generating 10KW for an hour, I have lost 5kwh.


Unfortunately that is not something that you can measure directly. When an inverter is curtailed, it is simply limiting how much energy it is producing. Since the energy is never produced, you can’t measure something that isn’t there. To determine how much energy is actually being curtailed involves calculating the energy that would have been produced by measuring irradiance and temperature at your panels as well as knowing what your system losses are between the panels and the inverter. This is done in commercial/utility systems using dedicated weather stations and simulation software such as PvSyst.

That isnt correct on a Solaredge inverter, it has a parameter called active_power_limit in the JSON returned from the API, that shows what percentage of the possible generation is currently being generated, eg if you have a 10kw inverter and it would otherwise be producing 10kw, but is currently limited to 5kw, it will have a value of 50%. If you would be producing 7.5kw, but are limited to 5kw, it would show 67% etc.

Yes, but that parameter represents the power limit relative to the maximum rating of the inverter. It does not represent what is available from the output of your modules. i.e. if the value reported for a 5kw inverter is 50%, then the inverter will be limited to 2.5 kW. But if there is only enough sunlight to produce 4kW, then your are actually only “losing” 1.5 kW of production and not 2.5 kW. The inverter does not know how much irradiance (sunlight) is available and thus cannot make calculation or measurement to determine how much production is actually being curtailed.

This is something we run into all the time with Utility Scale PV projects that I’m involved with (100 - 200 MW in size). It takes many hours of post production data processing to determine how much energy production we’ve lost if a site is curtailed.

Hi @dmaunder. I was going to respond but @pjschaffer has done that.

If you could dynamically increase your load better determine how much forgone generation there is. You could also log the ACTIVE_POWER_LIMIT as a BOOLEAN so that PVO captures the times when your inverter is being throttled.

More crudely if you could find a similar system near you [ in PVO ] with a similar orientation of panels your could estimate the forgone generation assuming of course that the other system isn’t limited.

More drastically you could add a battery to absorb the surplus.


Another possibility of obtaining an estimate would be to use something like which is what @pjschaffer mentioned above.

I have a 10kw inverter with 12kw of panels, but a 5kw export limit, so in that case, I think the figure is showing the uncurtailed generation amount, with the obvious ceiling of the 10kw that the inverter is limited to. If I divide the actual generation amount by ACTIVE_POWER_LIMIT, it shows it going up towards 10kw, then staying there as it hits the inverter limit.