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Old 07-25-2022, 09:01 PM   #1
Wits_End
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Are you at your Wits_End with electricity prices? I am. My 3 year 8.3c plan expired and the cheapest I could find on powertochoose was 15c with 60month plans, no thanks. Maybe the prices will come back down, but right now I am stuck with extremely high rates or long term high rates. Upon renewing I checked with my provider and thought I struck gold when I found an 11.5c rate (luck is all I can figure). In either case, the solar investment seemed to become reasonable.

For the longest time I couldn't get the math to work out. With reasonable estimations, a federal tax credit, and complete DIY system I was looking at 7 year return on investment. To me that is way to much risk for potentially getting my money back in 7 years and then trying to keep equipment up and running to actually make some money. The equipment warranties didn't support this.

Two recent events pushed me over the edge, high electricity prices and the discovery of lightly used solar panels for less than half price. Both brought the ROI to about 3 years.

I've done the math, gone through the approval process, have installed the system and it has been operating for about 2 weeks. The power I am getting is dead on with my estimations.

To me this is a trial effort to understand the system, understand true efficiencies, and calculate true ROI for my system. What this is not is an attempt to go off grid or have power when grid goes down, I have a generator for that. My long term plans is to add an equipment shed to the property and line it's roof, tripling the system size and basically providing all of the power I need.

Oncor agreement to operate - I thought this was going to be a major PITA so after I had a good idea of the system, I started with this process. If they wanted something changed or denied it or it took more time than my patience could handle I didn't want to have the money tied up in equipment sitting in the garage. I will say this was the easiest and most straightforward process I have ever dealt with in this type of job. From start to finish was about 3 days. I did read every detail and made sure my documents were exactly as asked for. These were the two documents with exact verbiage asked for. The information box was not requested, but I figured it wouldn't hurt.

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After approval, I proceeded to purchase all of the equipment, which all arrived within a week.

Hardware:
Solar panels (21x) (no warranty) - Jinko 395W - $175/each - $3,675 (used, about 1-2 years old)
Grid Tied Inverter (10yr warranty) - SMA Sunnyboy 7.7US - $1758 shipped
thepowerstore.com is located locally and shipped extremely fast, even though the website said 4 week delay
Wire for DC side - Temco 10awg solar wire - $233
Connectors - DC Side - $25
AC cutoff box Eaton DG222NRB - $152
Steel (cpurlin, receiver, 2x2 thick walled, angle) - $750
Conduit - $75
Total - ~$6700

Solar Panels - Installed 21 total, 3 rows of 7 panels which is about the max I could install with still having walkable room to service them.

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Install - Carport roof - I would never install on my house roof. I fight enough water issues and one simple missed leak would kill the savings I could achieve in a lifetime. I have a mueller 24x24 carport that I installed a few years ago. I decided to build a frame over the top of the carport and basically add another roof made of solar panels. This could be any roof, shed, shop, barn, etc. IronRidge makes awesome adapters to mount rails to Rpanel roofs, and their rail system is easy peasy. I did not go this route as it was going to cost a bit more and required more planning.
All Cpurlin and receivers were precut, predrilled, and ready to be bolted together. I did all of this under the carport's shade. Solar panels were installed with bolts and fender washers, basically sandwiches them down.

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Wiring - Each row was wired into a series of panels so Row A, Row B, Row C,
the results was 6 total wires (3pos, 3neg) ran into the garage to the inverter, which allows up to three DC circuits. The 10/3 AC side wires were run through the attic and down the wall and then penetrated through the wall to the outside where the Eaton shutoff was located, near the grid power meter. It then came right back in and into the breaker panel.

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Power
21 panels at 395w is about 8,300watts DC, due to inefficiencies, heat, mounting, etc my system is maxing out about 6,500watts midday.
Average is about 49kwh per day. So in July a total of about 1,400kwh, with mostly sunshine days.

Max the inverter input is 12,500w of solar power or about 31 panels, but max inverter output is around 7,700watts AC. Any extra power you generate over 7,700 is wasted, but the more panels you have the sooner you get to that max and the longer you stay at that max, therefore increasing power generated. You can roughly see this in the red line I drew on the chart. I'd like to add 15ft to my carport for another vehicle to park which would allow me to add more panels to the existing rows. I would do better to install about 3 more panels per row.

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The following is the spreadsheet I created during my initial estimation efforts. At 8.3c it was not worth it, but at 11c+ it makes more sense. It shows my average usage per month over the last few years. With efficiencies added in I was predicting about 1,300w in July, I think I will be very close to that. Winter months output will drop off due to less sunlight.

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I am estimating to generate about 40% of the total power I use.
All in all it took $6,700 and about 12 hours to build and install, not counting running around time to get metal or panels. Based on total cost and fed tax credit, 11c/kwh I am looking to recoup my cost in about 3 years, at 16c it would be 2 years. Even if I am off a year, it still seems like a reasonable investment. The inverter has a 10 year warranty and the panels should last 25years, who knows.

I don't plan to get rich off of the savings and for most people it is simply not worth it. It wouldn't even be a consideration if I had to pay someone or if I had to mount it on my roof. Time will tell.
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Old 07-25-2022, 09:39 PM   #2
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Awesome job on the project and write up! Thanks for sharing the info.

Curious about a couple of things. Did you need/get approval from the power company as well as the city/county inspector?? Are the panels readily available or was it one of them fortunate deals you hunted down??
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Old 07-25-2022, 09:51 PM   #3
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Quote:
Originally Posted by Pedernal View Post
Awesome job on the project and write up! Thanks for sharing the info.

Curious about a couple of things. Did you need/get approval from the power company as well as the city/county inspector?? Are the panels readily available or was it one of them fortunate deals you hunted down??
Power distribution is Oncor which I needed approval from. Power provider i did not. Most plans you only pay for what you use, solar spins meter backyards during day. I would not get money from over producing on a monthly basis.
No city here, no county approval required.

Solar panels can be found all day everyday at this price. Some are lower wattage but are way cheaper, just requires more surface area.
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Old 07-25-2022, 10:13 PM   #4
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Great writeup and illustrations! Thanks for posting this.
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Old 07-25-2022, 10:14 PM   #5
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Quote:
Originally Posted by Wits_End View Post

Solar panels can be found all day everyday at this price. Some are lower wattage but are way cheaper, just requires more surface area.
Did you purchase the used panels from the local shop, an individual or shipped from another source?
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Old 07-26-2022, 06:25 AM   #6
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Quote:
Originally Posted by Michael View Post
Did you purchase the used panels from the local shop, an individual or shipped from another source?
I found them on Facebook marketplace.
They were originally intended for a huge solar field somewhere in texas. There was a small manufacturing defect, missed solder joint, inside the rear box on a small percentage of them and so the entire lot of them were removed. This guy buys them, tests them, repairs them, and sells them. I watched him fix a few and then reseal that box with caulk.
Seemed low risk to me. I can watch the DC voltage on each row and verify all are outputting.

I found 7 year old 250w panels for $45 each. I found 400w panels with cracked glass, repaired with urethane, for $120. I decided to go more expensive and less risk but it was a hard decision as i could have saved tons of money on the panels.
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Old 07-26-2022, 07:24 AM   #7
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Very Interesting great info THANKS
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Old 07-26-2022, 07:32 AM   #8
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Now thatís how to do a DIY write up !!!!!
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Old 07-26-2022, 07:37 AM   #9
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Old 07-26-2022, 02:17 PM   #10
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Great recap! And the pics help a lot!
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Old 07-26-2022, 08:43 PM   #11
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Solar Inverter Installation Options:
Traditional single string inverter - All panels are in series and outputting DC voltage, pos to neg to pos to neg, etc, typical panel is about 43V loaded and a group of panels simply adds up, my case, 7 in a row so about 300V. Three different rows would each have 300V on the wires and all run back to the inverter, 3 sets of wires. Cheapest, easiest to install, only issue is if some panels are covered by shade the entire row goes down. This is what I went with for the trial install. I do not have shade around the carport so no worries about that.

Microinverter system - each panel is converted from the 43V DC to AC, wires running from solar panels to a box that combines, monitors, and controls all the microinverters. No single inverter to go bad and each panel is independently monitored for it's output. More efficient, no worries about shade on part of the system, all panels act independent, wiring is more complex due to specialized cables, would have cost me about $3k more overall, not worth it in my case, but I will say it looked appealing.
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Old 07-26-2022, 08:51 PM   #12
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I'll toss in another tidbit of info tonight.

Dirty panels

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Powerwashed

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One day apart, same cloud cover, same temperature outside
Dirty - 46.8kW
Clean - 51.5kW
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Old 07-26-2022, 09:00 PM   #13
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Great job on the DIY! 12 hours?!? Very impressive! I did mine for about the same cost and my output, at peak, is 6533 watts even though I have 8.2KW of panel due to losses and max inverter input/output. I went microinverters as I got the panels and inverters new from a wholesaler VERY cheap. I went 5x4 array with 395s.

Mine are pointing almost due south at about 25 degrees. That's taking the edge off of my max output during the summer but I'll get a bit more in winder so it's balanced out. I played around with the NREL solar calculator to estimate max total annual outut.

Keep all your receipts and use them as a tax CREDIT. It is still 26% of your total you'll not pay in taxes so factor that into your payback.

I estimated about 13,000 KW annually and I'm running about 10% above my estimates so far.

My COOP was net metering which meant that I would get 100% credit for every watt I push back but they ended that and it's now only about 5.5 cents they buy it for. It's better than zero but it added at least a year to my payback...

Also... be glad you got the newer panels. I've read a lot of people buying used and finding they are only getting 40-50% of the rated output and they are less than 10 years old.

Last edited by ken800; 07-26-2022 at 09:12 PM.
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Old 07-26-2022, 09:27 PM   #14
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Quote:
Originally Posted by ken800 View Post
Great job on the DIY! 12 hours?!? Very impressive! I did mine for about the same cost and my output, at peak, is 6533 watts even though I have 8.2KW of panel due to losses and max inverter input/output. I went microinverters as I got the panels and inverters new from a wholesaler VERY cheap. I went 5x4 array with 395s.

Mine are pointing almost due south at about 25 degrees. That's taking the edge off of my max output during the summer but I'll get a bit more in winder so it's balanced out. I played around with the NREL solar calculator to estimate max total annual outut.

Keep all your receipts and use them as a tax CREDIT. It is still 26% of your total you'll not pay in taxes so factor that into your payback.

I estimated about 13,000 KW annually and I'm running about 10% above my estimates so far.

My COOP was net metering which meant that I would get 100% credit for every watt I push back but they ended that and it's now only about 5.5 cents they buy it for. It's better than zero but it added at least a year to my payback...

Also... be glad you got the newer panels. I've read a lot of people buying used and finding they are only getting 40-50% of the rated output and they are less than 10 years old.
12 working hrs is about right. I did have a helper for about half of the work. I guess I didn't explain the time it took to decide on what equipment, design it all, and draw up plans. But I did most of that on rainy days.

I took into account 26% tax credit. Wish I could add in the install costs most companies charge.

My install is about 3 deg. Best for summer is 9 deg and best for winter is 45 deg. Overall best is around 28 deg. My original idea was to add in adjustable legs on the entire frame and use a highlift jack to adjust, but with my install the panels blend in to the carport, which I prefer.
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Old 07-26-2022, 09:53 PM   #15
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Well done MrEnd. I really like how you bolted and didnt simply weld the panel frame.
Thanks for posting your experience and breaking it down Barney style.
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Old 07-27-2022, 12:22 AM   #16
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Very good info, thank you sir!
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Old 07-27-2022, 11:46 AM   #17
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Quote:
Originally Posted by Briar Friar View Post
Well done MrEnd. I really like how you bolted and didnt simply weld the panel frame.

Thanks for posting your experience and breaking it down Barney style.
The thought was that I could easily remove the entire frame and do something else with it if the panels didn't work out.

If I was patient the square tubing would have been bolted as well, but i didn't take the time to think of a bracket and didn't want to spend time on a ladder trying to match drill through thick metal.
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Old 08-05-2022, 10:36 AM   #18
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Has anyone found a good honest set of data that looks at panel efficiency over time? I have read some horror stories of 40-50% losses at 5-7 years. That breaks the math.
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Old 08-05-2022, 10:47 AM   #19
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Quote:
Originally Posted by 175gr7.62 View Post
Has anyone found a good honest set of data that looks at panel efficiency over time? I have read some horror stories of 40-50% losses at 5-7 years. That breaks the math.
This is the problem. About the time that you are supposed to break even, the panel efficiency degrades to the point where the investment is no longer worthwhile. There are better panels on the horizon that may address this.
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Old 08-05-2022, 11:04 AM   #20
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Amazing write up. Will likely come back to reference when I'm in a position to review solar for my home.
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Old 08-05-2022, 12:15 PM   #21
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Very cool. How difficult to get tax credits? Is it just a major pain in the arse?
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Old 08-05-2022, 07:00 PM   #22
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From my memory, new solar panels are warrantied for like 25 years with guarantee of 80%. 5-7 years is a huge delta from that. I should be able to tell you after a year if the efficiency is dropping as bad as you are saying, that is approximately 10%/year, should be pretty obvious.

So far i am achieving exactly what i estimated. Ill update next week after 1 month operation.

The federal tax credit is easy, you enter the total you spent on one line on tax form. I imagine this stupid inflation reduction bill is going to add additional credit.
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Old 08-08-2022, 07:57 PM   #23
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1 month update, July 9 - Aug 8


21 panels rated at 8,295 W
Total energy generated in 1 month is 1,420 kWh.
I estimated 1,280 kWh for the month of July and again for August, so a little better.
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Old 08-09-2022, 07:36 AM   #24
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Quote:
Originally Posted by Wits_End View Post
1 month update, July 9 - Aug 8


21 panels rated at 8,295 W
Total energy generated in 1 month is 1,420 kWh.
I estimated 1,280 kWh for the month of July and again for August, so a little better.
Impressive sir, well thought out DIY.

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Old 08-09-2022, 07:52 AM   #25
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Great project write up Thanks for sharing sir!
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Old 08-09-2022, 08:13 AM   #26
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Nice! As someone who is pretty anti-solar, keep posting follow ups because real world data always trumps what some salesman says, much less my neanderthal brain. I hope it all keeps going well. That would make me at least run the math for my own home if it does!
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