Not getting my production guarantee

[mnhim001]

Hi guys, I am new to solar panels. I have been producing power for 1 year now and by looking at my Enphase Envoy I have produced a total of 7,798.73 Kwh, but what I was guaranteed was 9,996 Kwh annually.

Would this be considered a signficant change where as I need to contact the installer and have them check?

As far as I know, I am using 20x Solar World 280 with 20x Enphase M250 Inverters.

[J.P.M.]

Before you contact anyone, if you haven't done so already, start with your own estimate of annual output from PVWatts and see what the system might produce. Then, read the contract you signed with respect to production guarantees. Then, have the vendor check your monitoring equipment for proper setup and operation. The difference may be in faulty reporting/monitoring.

7,798 vs. 9996 kWh/yr. is probably a greater variation than might be reasonably explained by weather variation but it's possible even though unlikely.

More shading than anticipated may be possible. Micros will help the unshaded portion of an array produce power otherwise lost when using string inverters, but cannot restore energy lost from shading.

[mnhim001]

I am in Los Angeles, so weather hasn't been an issue. Their are also no trees above the roof.

How can I do my own estimate? The only numbers I have to go by are that of the monitoring equipment, but if that is faulty then how can I get this accurate?

[J.P.M.]

I am in Los Angeles, so weather hasn't been an issue. Their are also no trees above the roof.

How can I do my own estimate? The only numbers I have to go by are that of the monitoring equipment, but if that is faulty then how can I get this accurate?

Google "PVWatts". It's a PV modeling tool from NREL. Read all the help/info screens a couple of times for some idea off what you'll do, what to expect for model output and what it may mean.. Get your array orientations right and use 10 % system loss parameter rather than the 14 % default value. Then, make a few runs. The whole process ought to take maybe 20 minutes or so.

You'll have a better idea of what's going on with your array, and maybe not get quite as intimidated if you call the vendor or make a production warranty claim. Sounds like you have a lot to learn.

[mnhim001]

I am not sure if I am doing it correctly, my results are: 9,102,854 kWh/Year with a 10% loss

My Kw system size is 5600
Tilt: 20
Azimuth: 180

Does that seem accurate to you?

[ButchDeal]

I am not sure if I am doing it correctly, my results are: 9,102,854 kWh/Year with a 10% loss

My Kw system size is 5600
Tilt: 20
Azimuth: 180

Does that seem accurate to you?

are you sure your array is 100% due true south (not magnetic). Also are you sure you read that right 9 million kWh/ year is a bit off. did it say kWh or Wh ?
Also are you sure you don't have shade from anything at any time of day, other houses, trees, vent pipes, dormers, chimney, etc?

[mnhim001]

are you sure your array is 100% due true south (not magnetic). Also are you sure you read that right 9 million kWh/ year is a bit off. did it say kWh or Wh ?
Also are you sure you don't have shade from anything at any time of day, other houses, trees, vent pipes, dormers, chimney, etc?

I've read it right, and I copied and pasted those numbers.

I guess their may be a small portion in the shade. I've attached a satellite view of the roof of my house. I don't think those in the shade make such a significant loss in kwh per year does it?

[SupraLance]

Assuming north is up in the pictures, do those panels on the East roof face East right into those trees? Maybe an actual picture or 2 would help us see the tilt, but if those panels are not all facing the same way at the same tilt, you will have to run each array separately in PVwatts and sum the total.

[mnhim001]

Assuming north is up in the pictures, do those panels on the East roof face East right into those trees? Maybe an actual picture or 2 would help us see the tilt, but if those panels are not all facing the same way at the same tilt, you will have to run each array separately in PVwatts and sum the total.

The panels on the east roof looks like they are facing east, I am going to have to figure out how to get up there since its a 2 story house.

Here are some information I gathered from the MyEnlighten software:

4 Arrays:
RP Azimuth: 180 Degrees
South Azimuth: 180 Degrees
West Azimuth: 270 Degrees
East Azimuth: 90 Degrees

[J.P.M.]

I am in Los Angeles, so weather hasn't been an issue. Their are also no trees above the roof.

How can I do my own estimate? The only numbers I have to go by are that of the monitoring equipment, but if that is faulty then how can I get this accurate?

If you had an entire array of 5.6 kW facing dead, true south @ a 20 deg. tilt and unshaded, you could expect probably 9,500 - 10,000 kWh/yr. generation.

The reality looks like what you actually have is four orientations and shading situations. Given all that, and what those different orientations and unknown (to us here anyway without the benefit of being on site) shading can do to reduce annual generation, 7,798 kWh/yr. actual production doesn't seem all that far out of line.

As for what you think you got from PVWatts, no rooftop array will produce 9 million kWh/yr. If PVWatts is telling you that, you have an error in your input. I might believe 9,100 or so kWh/yr. for a south facing array, but what you report is about 3 orders of magnitude too high. And, to reiterate, you have 4 orientations, three of which are not as good as south facing, and one of those (the east) looks like it's shaded for a portion of the morning most of the year.

[ButchDeal]

I've read it right, and I copied and pasted those numbers.

I guess their may be a small portion in the shade. I've attached a satellite view of the roof of my house. I don't think those in the shade make such a significant loss in kwh per year does it?

small portion in the shade?? your kidding right? you have trees to the east, roof to the west, not to mention solar on east, west, and south roofs.

East facing are directly shaded by trees,
west facing are shaded by the several roofs,
south facing are shaded by trees to the east, and roof to the east

and that is just what I can see in the close cropped image you uploaded.


Further you stated you did the pvwatts simulation with the full array south facing, it isn't.

[ButchDeal]

The panels on the east roof looks like they are facing east, I am going to have to figure out how to get up there since its a 2 story house.

Here are some information I gathered from the MyEnlighten software:

4 Arrays:
RP Azimuth: 180 Degrees
South Azimuth: 180 Degrees
West Azimuth: 270 Degrees
East Azimuth: 90 Degrees

A photo from the ground showing the height of the trees next to the building is all.

it looks like you have two modules facing west
6 modules facing south on two different arrays
10 module facing east on two different arrays

so that counts out to 18 PV modules, but you thought you had 20?

[mnhim001]

A photo from the ground showing the height of the trees next to the building is all.

it looks like you have two modules facing west
6 modules facing south on two different arrays
10 module facing east on two different arrays

so that counts out to 18 PV modules, but you thought you had 20?

I should have 20 panels, I know I have 20 inverters as they show up on my monitoring system. Is it safe to say if I have 20 Inverters, I should have 20 panels?

I am no expert, and that is the reason I put my trust on these solar contractors to do it correctly. I've been trying to get a hold of them for the past week I've left them voicemails, and email and they have not responded back to me at all. Its frustrating when I paid for a certain amount and am not getting what I paid for.

[ButchDeal]

I should have 20 panels, I know I have 20 inverters as they show up on my monitoring system. Is it safe to say if I have 20 Inverters, I should have 20 panels?

I am no expert, and that is the reason I put my trust on these solar contractors to do it correctly. I've been trying to get a hold of them for the past week I've left them voicemails, and email and they have not responded back to me at all. Its frustrating when I paid for a certain amount and am not getting what I paid for.

yes if you have 20 enphase micro inverters you should have 20 PV modules. the photo is not that clear so maybe I missed two in my count.

[SupraLance]

I am going to have to figure out how to get up there since its a 2 story house.

Google driveby? Or just pictures from the ground could give us an idea what we are really looking at since aerial doesn't show heights of trees or slope of panels.

4 Arrays:
RP Azimuth: 180 Degrees
South Azimuth: 180 Degrees
West Azimuth: 270 Degrees
East Azimuth: 90 Degrees

This tells me that the panels on the East/West roofs truly point East/West. I wonder if RP Azimuth means we are seeing an array on the north sloped roof that is propped up to face south?
A quick PVwatts run of 5600w pv in LA tells me that the production numbers they quoted you are unrealistic without tracking. 5600w at optimum fixed tilt on a south roof only produces what they quoted if you assume only 4% losses (which mean no soiling, no shading, no production irregularities etc.). And that's without even accounting for the fact that some panels face East/West.