Will two Chint 6kW inverters work for a 15kW array?

Hello,

I'm looking at a 15kW installation using (60) ReneSola 250M-24/Bb panels.

The normal derate I would use for inverters is 20% but in the installation manual for the Chint inverters it states that you can use up to a 30% derate. With a 20% derate, I'd go with (2) Chint 7kWs for this installation. With a 30% derate, I'd go with (2) 6kW inverters.

Using PVSelect to run the string sizing, it states that running 3 strings of 10 panels per inverter is fine for both the Chint 7kW and 6kW. I'm hesitant to go beyond the normal 20% derate but if using the 6kWs would be no problem it would save a few hundred dollars on the installation.

What would you recommend?

Doug

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Doug,The real question here is related to the project: Is it better to have closer to 6kW (max) AC for the whole year, or does the project need 7kW AC in the peak production season (Summer, Time of Use, etc)?

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This project is going to be installed in the Missouri market where there is currently a $2.00/w state rebate for installations up to 25kW (DC). The utility rates are not based on Time of Use.

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30% is a little aggressive unless you know that the local conditions justify it. The money that is saved up front can be lost many times over over the life of the project if you are not able to fully use the energy from the PV array.
You need to run the system through an energy production simulation using SAM, PVsyst, or a similar application to see if you can use that high a derate and still maximize the energy production from the system.

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