Large Difference in Annual Production Between “Inject to Grid” and “No Injection” Despite Same System Configuration

[mingsolar]

Hello,

I’ve run two PVsyst simulations for the same rooftop PV system on a warehouse in Malaysia. Both simulations have identical parameters:

• System size: 3423 kWp (6339 × JinkoSolar JKM-540M-72HL4-TV)

• Inverters: 12 × Sungrow SG250-HX (total 3000 kWac, Pnom ratio: 1.141)

• BESS: 2 × Huawei Luna2000 (2936.4 kWh usable capacity)

• Orientation: 6 fixed tilts (e.g., 13°/-20°, 13°/160°, etc.)

• User load: Fixed profile, ~4800 kWh/day (1,752,000 kWh/year)

• Self-consumption strategy with battery charging from PV surplus and discharging to support load

The only difference between the two runs is:

• Case 1: Grid injection allowed (Grid reinjection: Yes)

• Case 2: Grid injection not allowed (Grid reinjection: No)

However, the annual "Produced Energy" output differs dramatically:

• Case 1 (Inject): ~4.97 GWh/year, PR = 82.27%

• Case 2 (No Inject): ~1.74 GWh/year, PR = 28.81%

Other metrics like EArray, E_InvOut, and load-supplied energy (E_Solar = 1.74 GWh, SF = 99.26%) are identical in both cases.

My questions:

1. Why is the “Produced Energy” (and PR) so much lower in the no injection scenario when the PV array performance and load supply remain the same?

2. Is PVsyst not counting excess PV generation as “Produced Energy” when it is curtailed (i.e., when the battery is full and there's no injection allowed)?

3. Is there a better way to represent "total generation potential" in a self-consumption system without grid injection, so that I can compare energy yield more realistically?

I want to ensure I'm interpreting these results correctly, especially for techno-economic reporting under self-consumption-only policies (e.g., Malaysia’s SELCO guideline).

Thank you!
 

 

[André Mermoud]

Your questions: 

Why is the “Produced Energy” (and PR) so much lower in the no injection scenario when the PV array performance and load supply remain the same?

You have a system of 3.4 MWp, this probably produces more than 17 MWh during a clear day. Now during this day the internal consumption is 4.8 MWh and the possible storage is 3 MWh, therefore 7.8 MWh. If you don't reinject into the grid, you will have more than 9 MWh lost ! 

Is PVsyst not counting excess PV generation as “Produced Energy” when it is curtailed (i.e., when the battery is full and there's no injection allowed)?

In this case the energy is indeed not used (it is even not produced), it is quite logical that it is named "Unused energy" 

Is there a better way to represent "total generation potential" in a self-consumption system without grid injection, so that I can compare energy yield more realistically?

Why a better way? The "Total generation potential" is indeed the sum of the used energy and the unused energy, this seems quite clear for the user.