Is this solar output low?

[ryanPSD]

Good morning, I'm in the process of purchasing a house that has an owned 9.6 kW solar array installed around November 2014 to February 2015. We are in central/southern California, lots of sun.

Per the solar performance/analysis documentation provided by the contractor when the system was purchased, they projected it should generate 16,543 kWh per year. I guess one question, now that I write this, is: how accurate are these projections?

The house has 30x (thirty) SunPower SPR-E19-320 panels, with 2x (two) SMA America SB5000TL-US-22 inverters. They specify the panels were installed with 22* tilt, azimuth 185*, if it matters for this topic. There is zero shade on or near the array, year round.

I've received PG&E statements from the owners for July 2016 and December 2016 that show:
July kWh consumption: 1,671
July kWh solar generation: 634
Dec kWh consumption: 1159
Dec kWh solar generation: 429

I did not receive other statements, but the December statement shows the year's net kWh usage (just no total consumed or generated, to determine one from the other), but their relative trend of net usage looks right based off these two month's net usage.

Anyway...

I'm not sure if I'm missing something, but this (the kWh generated) seems low to me?
Are the numbers provided by the utility company for kWh generation accurate?

Every time I try to calculate output myself, I usually come up with around double the kWh produced (much closer to the contractor's projection) compared to what these bills state. Is there some sort of real-world variable I'm missing? The panels appear clean and the system visually is in good shape, as is most everything else in the house. They took care of things.

Looking for thoughts? Thank you in advance!!

Ryan

[sensij]

PG&E only sees the kWh that are pushed back into the grid. The energy that is consumed on premises by your household loads is not detectable by their meter. Many inverters offer a way to see how much they report being produced, either directly on the unit or via a web portal, if connected. That will give you a better idea of what is actually being produced.

[J.P.M.]

Run PVWatts and confirm estimates from vendor. Read the help/info screens before you do any runs. That 16,543 from the vendor looks about right, maybe just a bit optimistic, but certainly possible and believable. The orientation you post is close to optimal. The equipment is reputable, well known and quality stuff.

The generation you post does look way low for that size system. Is that total generation or excess generation ? FWIW, the consumption numbers you post look more like system generation numbers.

Have you contacted the vendor ?

I'd check and confirm what you're looking at and make sure you understand what it's telling you.

[SunEagle]

My first question is what were you consuming before you installed the solar?

To me that 1671kWh you consumed in July is what you purchased from your POCO and the 634kWh is what you sold them. There was no measurement of what you actually generated by your pv system or what you would have purchased if you did not generate.

[J.P.M.]

My first question is what were you consuming before you installed the solar?

To me that 1671kWh you consumed in July is what you purchased from your POCO and the 634kWh is what you sold them. There was no measurement of what you actually generated by your pv system or what you would have purchased if you did not generate.

Sounds like the OP is considering purchasing the home where the system is installed.

Looks like you and I agree that what the OP has posted looks like production and excess generation.


If the system has the same SP monitoring I have, prior system generation is available.