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Stand Alone System - Missing Energy


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I'm working on a stand alone system and have a question about the simulation result.

Actually the system is producing way to much energy compared to the consumption.

Excess Unused Energy is 1437 kWh per year

But still there is a Missing Energy Quantity of 97kWh per year.

I don't understand that to be honest?

Hope someone can help me out

Many thx



Missing Energy.jpg

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many thanks for your reply. Yes I have noticed that the missing energy can be seen in the diagram per month. 

I'm playing a bit with the simulation of PVSyst with different Off Grid Designs. I must say that I don't understand

the behavior of the simulation completely. But probably that's because of my lack of knowledge (-: 

I also don't understand all terms mentioned in the simulation report. I hope you can help me out. I already want to thank you for that. 

First the load profile for the stand alone system:


The first system I designed has the following components:


3,300 Wp  PV Modules Longi 6 x 550 Watt Mono

Lithium batteries 3 x 48volt 100Ah

Outback Flex Max 60

The main results for this system are:image.thumb.jpeg.180176d05a92cfd6bf86ce73bbb9b0cd.jpeg

Actually there is a lot of excess (unused) energy.

The performance ratio is bad 55%

Missing energy is only 1.6% of the time, that’s good


How can we make this system better?

By better I mean:

Better Performance Ratio

Less unused energy.

Since there is a lot of unused energy I would expect that we can make the system smaller:

The second system I designed has the following components:

2,200 Wp  PV Modules Longi 4 x 550 Watt Mono

Lithium batteries 3 x 48volt 100Ah

Morningstar Tristar 45 36 / 48

The main results for this system are:


I have the following questions about these main result:

How can the specific production be 720 kWh/kWp/year compared with 1661 kWh/kWp/year of the first design. I would expect it to be close to each other.

The available energy is absolutely not enough to support the daily consumption of the household. 10.5 kWh.

365 x 10,5 kWh = 3833 kWh

Available energy = 1583 kWh

How can the simulation mention unused energy 1346 kWh, that is not possible in my view. There is a lack of energy of 3833 - 1583

How can the simulation mentioned missing energy 0 kWh / year

How is this possible?

Actually this looks like the most optimal system.

Performance ratio is good, no missing energy. So this looks like the best solution. But I really have my doubts about it. But I hope you can explain it to me.

Can you give some explanation about the terms


And why does the simulation of design 2 gives a battery life of 5 years while design 1 doesn’t?

Many many thanks

Kind regards












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