Solar production. Panel ratings/claim vs reality

[ericm979]

I think one advantage to roof mount panels in the summer anyhow is that the panels shade part of the roof.

 

[LD1]

Did lots of research today. Lots of options. Enphase micros seem about the best....but there are other micro inverters too. Some do two panels per.

Looking at kits....but don't know if the "kits" are more expensive for convenience or cheaper because it's a package.

I have seen panels asl low as 25-30 cents per watt.

10kw system would be about $3000 worth of panels.

Ive seen the micro inverters for $150-$200. I guess since one per panel is needed....I should pay attention to getting higher wattage panels to reduce the number of those needed. But about 26 390w panels puts me close to 10kw

So about $5k for the inverters.

That's $8k right there. But a lot of the 10kw "kits" I'm seeing are $15k with no racking. And ground racking adds $3k but I still need structure pipes sourced locally.

Is there really another $7k worth for the cables and combiner box and other odds and ends to connect all the panels together? I'd still have to buy the service wire to go from there to house too.

Looking like "kit" options are gonna push the final product to ~$2 per Kw. Bout $20k for a 10kw system.

Don't seem to be many good options for sourcing stuff. Not sure how much I trust the places selling the kits online cause there aren't many. And I'm sure they are making quite the markup.

 

[LD1]

Consider also that while a panel may be, for example, a 350W panel, you may or may not spec the inverters (microinverters these days) to the same maximum.

I have 10kW of DC (panel maximum output) but my microinverters will put out a maximum of 7.68kW AC. The microinverters will unlikely degrade at the same rate as the panels, and the panels will only put out their rated maxima at very specific conditions (angle of incidence of the rays, temperature) and it was explained to me that while I could potentially end up with a few more AC watts in the first few years of operation, the extra cost for higher output microinverters would never come close to being paid off.

In other words - don't think your 10kW of panels all added up together will give you 10kW.

I was also concerned about putting panels on my roof: 1, my roof wasn't exactly new, but it wasn't old enough to require a re-roof yet; 2, my roof hip is aligned N-S and I couldn't easily tilt panels at all toward the south; 3, some shading of the roof.

Due to setbacks here, my 8ac of land had a 50'x50' region that allowed new "structures" to be placed on it (we have to be 100' away from water, 30' from property lines, and other places have bad shade in the mid to later afternoon). I'd imagine I could've gotten a variance because a solar ground mount isn't particularly polluting to water features (meanwhile I can plow and run cattle right next to the pond and irrigation canal but I can't put concrete into the ground?) but I went with the easy spot because it really had the best sun. Still, it was a 550' cable run from the panel mount to my service entrance; the trench and the cable added to the mount itself weren't particularly cheap, but I can also clean my panels from the ground; I'm still a proponent of the ground mount (plus I intend to add 50% more on another ground mount next to it if I need to).

What does your 10kw system produce through out the year? What's January production? May? And maybe July to give me an idea

What latitude?

 

[ponytug]

What does your 10kw system produce through out the year? What's January production? May? And maybe July to give me an idea

What latitude?

Ours is a smaller system, with less than perfect orientation.

Dec/Jan is about 20% of June. If we were to pull the angle of the panels from about 20 degrees up to about 30-35 degrees, the winter production rises to about 40% of the summer production, though the summer production would take a 10% or so hit, per PVWatts. That's the plan for the next array.

All the best,

Peter

 

[LD1]

Ours is a smaller system, with less than perfect orientation.
View attachment 878366
Dec/Jan is about 20% of June. If we were to pull the angle of the panels from about 20 degrees up to about 30-35 degrees, the winter production rises to about 40% of the summer production, though the summer production would take a 10% or so hit, per PVWatts. That's the plan for the next array.

All the best,

Peter

What is your system size? And what latitude?

Looking at your spring/fall months....I would like to make right about double that.

I need to do some research on racking.

I definitely want to optimize the angle....maybe once every month or two.

Playing with the pvwatts calculator it seems to make quite a difference.

 

[Roric]

Our array is 7500 watt (375X20) via Solaredge optimizers and inverter.
Production is just short of 9 mega-watt-hours per year, just under 25
kilowatt hours per day. Located near central Minnesota so it may be applicable to your location, (except for snow loads). Roof mounted, fixed south orientation.
Our utility uses two meters: one bi-directional for the service and another for PV production. Monthly bill shows both totals.
When installed, it produced enough to exceed our use in the summer and resulted in a credit on the bill and in the winter we had a bill due.
On average it was a "wash".
Since 2019 we have done some energy saving changes (but also some energy using ones: A PHEV for her, EV for me). This has resulted in having a bill most months although it is small compared to pre solar.
So install as much as you can is what I can say.
The Solaredge app says we are on track to be at 45 MWH when we hit the 5 year anniversary date.
My favorite thing is when I turn off a light switch and say "Do you think we get free electricity around here?" SWMBO say "Yes, yes I do..."
Good luck with your self-install.

regards,

R

 

[LD1]

The "install as much as I can" will extend the payback. According to PVwatts estimate for generation.....a 10kw system will exceed what I use in my home 6 months out of the year but fall well short for the other 6 months.

I did a quick spreadsheet as if I had a 10kw system
Month..........usage............Potental generation........difference
Jan..............2124.....................716........................1408
Feb..............1615.....................805........................810
Mar..............1645....................1034.......................611
Oct..............1355....................1139.......................216
Nov..............1710....................786.........................924
Dec..............2085....................638........................1447

Those are the 6 months I fall way short and have to purchase all those KWH at 12.5 cents per kwh from the electric company

Apr..............1153...................1180.....................+27
May.............1282...................1379.....................+97
Jun..............1220...................1406.....................+186
Jul...............1466...................1545.....................+79
Aug.............1348...................1404.....................+56
sep..............1135...................1278.....................+143

Those are the 6 months I'd make more than using and get credited at 7.5 cents per kwh from the electric company

So ~5416 kwh I have to buy at 12.5 cents = $677
The ~588 kwh I made surplus Id get 7.5 cents credit = $44.10

And I have a monthly meter fee of $57 x 12 = $684

$677-$44+$684 leaves me with a $1317 electric bill for those 12 months.

The ACTUAL cost of those 12 months without solar, my bill was $2655 for the year.

If I had a 10kw system....in the past 12 months I estimate my savings would have been ~$1338

Looking for no more than a 10 year payback means I need to find a 10kw system....ground mounted, all racking, etc and spend no more than $13,350.

OR....factoring 30% fed credit.....no more than $19,000 for EVERYTHING.

Thats a tall order and I need to do some more shopping. But we are certainly closer than I ever have been in the past to possibly hitting this 10 year target

 

[Roric]

If the utility allows you to "over-size" production it is to your advantage.
(We were limited to 120% of historical use).
Make hay while the sun shines is the old saying.

NAZ lists a 11,200 system with Enphase inverters for $14,000.
Depending on your utility rules and regulations it may prove a faster payback. There is a value in taking a bill off the table every month.

best of luck,

R

 

[Roric]

My all-in cost was $14,000 in 2019
Minus 30% federal incentive was about $9,800.
Purchased kit from Wholesale Solar for about 9k.
All the rest of costs were rented and purchased locally.

 

[ponytug]

What is your system size? And what latitude?

7.6kW DC, 6.9kW maximum typical production due to orientation, roof planes, etc.

37N, so quite a bit south of you.

All the best,

Peter