# 12.2kw solar barn



## JP11 (Aug 19, 2014)

Day one of install was today.

Unfortunately.. I have to go back to work tomorrow and won't be here for the rest.

Good news.. Internet 'bridge' was able to work across my wires (install guys were unsure.  about 500feet underground wire, and two panels to go through), and I now have wired internet in the barn, which will let me view solar array in real time via web.

A couple pics.  Just boxes and racking.

JP


PS.. barn looks odd because my wife is a professional photographer.  Different backgrounds for her to work with .  The couple green ones are going to be a graffiti wall and a stucco wall.


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## peirhead (Aug 20, 2014)

Are you using Enphase microinverters??...what is your configuration....roof orientation etc?


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## JP11 (Aug 20, 2014)

Roof is 205 with a 4/12 pitch.
No microinverters. 
48 Panels that are 255W
2 SMA transformerless inverters.

It should be making power Thursday.  I don't get home till Tuesday.  Power company came by this monday and put in my dual meters.  I'm all set to go once they finish.

JP


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## jebatty (Aug 20, 2014)

Congratulations, very exciting. What are the net metering rules in Maine with your utility? 4/12 pitch is about the equivalent of what my ground mount is. Good compromise summer vs winter. Did you do a PVWatts analysis for your system? If so, what did it show? Keep the info coming.


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## peakbagger (Aug 20, 2014)

Time to buy out the local hardware store for roof rake extensions!


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## JP11 (Aug 20, 2014)

No raking up there.  walls are 16' high.  I did the PVwatts calcs.  In maine they won't cut you a check for excess production.  Credits roll for 12 months.  Over a year old.. you've given them away.

If it becomes an issue.. I own the house my parents are in.  I can put that house in my name.. and send extra credits to that account.

Eventually, the wife's next car will likely be a plug in.

Here's the info I got.

PVWatts: Monthly PV Performance Data
Requested Location:    
City: AUBURN-LEWISTON      
State: ME         
Lat (deg N): 44.05        
Long (deg W): 70.28        
Elev (m):  88        
Array Type: Fixed (roof mount)      
Array Tilt (deg): 33.3        
Array Azimuth (deg): 205        
DC Rating (kW): 12.24        
DC to AC Derate Factor: 0.77        
Average Cost of Electricity Purchased from Utility ($/kWh): 0.14        
Cost of Electricity Generated by System ($/kWh): 0.15        

Month AC System Output(kWh) Solar Radiation (kWh/m^2/day) Plane of Array Irradiance (W/m^2) DC array Output (kWh) Value ($)
1 580.762085 2.077308655 64.3965683 663.0841064 83.97
2 970.4955444 3.610863209 101.1041718 1073.975098 140.31
3 1278.183716 4.564380169 141.4957886 1417.144287 184.8
4 1355.656128 5.01350832 150.4052429 1503.063232 196
5 1625.287109 6.051045418 187.5824127 1787.557861 234.98
6 1442.623169 5.72269392 171.6808167 1599.946533 208.57
7 1485.337036 5.926843166 183.732132 1640.805298 214.75
8 1352.230469 5.228490353 162.0832062 1496.544556 195.51
9 1273.668701 5.048354149 151.4506226 1406.806152 184.15
10 1052.330444 3.823254824 118.5208969 1169.723511 152.15
11 705.9881592 2.622964621 78.68894196 794.2578735 102.07
12 733.9880371 2.522422552 78.19509888 817.9729004 106.12


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## CombatChris (Aug 20, 2014)

Wait, they don't buy back the excess power you make and only give you a credit which is thrown away if not used? Damn, that's a shame.

About this system - are you installing it yourself or are you having it put in by some contractors? Buy a kit? I've been doing tons of reading and research on this and I'm curious about all you've done. How much for the total install, if you don't mind my asking?


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## peakbagger (Aug 20, 2014)

You would be surprised with raking.  I rake the bottom edge of my panels on the second floor roof of my house which is about 20 feet from the ground. Just getting the bottom edge cleaned off after a snow dump make a big difference in how quickly the rest of the snow will melt and slide off. Unfortunately, like a metal roof, the snow sometimes decides to come down in one big sheet and you really need to hope you aren't under it as it can cause serious injury. Folks use snow clips on metal roofs to stop the avalanche but with solar panels you really want them to clear.

Bummer on the net metering, I am spoiled with the NH system where they never expire. They even will buy them back but at a fairly low rate once a year but I prefer to just run my heat pump to burn it up.

Since you went with central inverters it will be interesting to see how them wire them. I would suggest in horizontal rows as I find that on occasion I will still have snow on the top rows and the bottom ones will be clear.


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## JP11 (Aug 20, 2014)

Not sure how the schematic goes. I know there are 8 conductive wires.  So that means 6 panels per wire.

As for your questions.

Contractor
just a whisker under 35k.

Snow really didn't hang around on that roof last winter (my first with the building).  I guess it's just we'll see.  Panels don't go down to the part I could rake anyway.  Wife sent me a pic of today's progress.  I'll post

JP


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## JP11 (Aug 20, 2014)




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## Vic99 (Aug 20, 2014)

That's great, JP!  You are going to love it.  It's like magic.


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## Where2 (Aug 20, 2014)

JP11 said:


> No raking up there.  walls are 16' high.  I did the PVwatts calcs.  In maine they won't cut you a check for excess production.  Credits roll for 12 months.  Over a year old.. you've given them away.
> 
> If it becomes an issue.. I own the house my parents are in.  I can put that house in my name.. and send extra credits to that account.



Your program sounds like net metering to me. Only difference is at my house is I have one smart meter that tracks my Net and Delivered. Sounds like your power company installed a separate meter to track outgoing to subtract it from what you might buy. My credits (if I ever make any) don't roll past the end of the year. At the end of December I would get paid ~$0.03/kWh for any excess, and it just didn't seem right to generate excess for that little return.

In Florida, the power companies don't let you swap kWh between different accounts at different addresses. Some farmers who installed panels with multiple meters found that out the expensive way.

Thank you for the photos!


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## JP11 (Aug 20, 2014)

Yes.. it's as you describe.  Net metering.  I sell anything I don't use.. on a minute to minute basis.  I get to let them have that KW.. and I get to use it until it gets to be a year old.  Contractor said even though I'm oversized.. will take a LONG time for me to worry about credits going un used.

I SHOULD have web access to see production real time tomorrow... assuming they finish and set it up as promised.  

Been very happy with the installers.  I only met the 'roofing' guys, and not the electrician... but been very impressed with them thus far.

JP


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## maple1 (Aug 20, 2014)

Do I have this figured out right?

The most return you would get in a year would be what your power bill would have been in a year? If you generate more than you use, they resell it but they don't pay you for it?

I'd be looking at a 25 or 30 year payback if I understood right.


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## Where2 (Aug 20, 2014)

maple1 said:


> Do I have this figured out right?
> 
> The most return you would get in a year would be what your power bill would have been in a year?


^^^ Sounds about right. With my undersized system (4.4kW), I still had just under $500 in total electric bills for the last 12 months. That beats the heck out of the $1500 I had in total electric bills in 2012, in my all electric house with all the creature comforts. My co-workers spend anywhere from $1500-$2500/yr on their electric bills. I'm not planning on selling my house any time soon, so 12-15 year pay back does not discourage me. (my system is 4.4kW, because that was the max I could fit on my second story south facing roof). Even if I had a system that generated every kWh my house uses. I'd still have close to $100 in total bills for a year, since my base meter fee is close to $8/mo.


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## JP11 (Aug 21, 2014)

Maple.. I'm guessing your power is quite a bit cheaper than mine.  I had calculated payback at around 11 years.  The week after I sent in the deposit, PUC announced rates going up 4%. 

I've got a spreadsheet going, and plan to put in production numbers, and let it extrapolate out and average to see where it crosses over.  I'm only 40.. and plan to stay in my house a good long while.

There is a tax CREDIT of 30% of installed cost.   You need to of course be paying that much in taxes to have it work out.  

The numbers all scale rather well.  I have power bills in the 2k per year range.. I should have zero usage with this setup.  Bill should be around 12 dollars a month.

I think my install is about as simple as it gets.  Flat, south facing roof.  Didn't have attic insulation in.  Other than the walls being insulated and sheathed, they couldn't have asked for it to be any easier.  I even let them use my forklift.. so no lugging anything.

JP


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## jebatty (Aug 21, 2014)

Agreed you should end up with a near $0 bill. I added up your PVWatts estimated average AC Output = 13,855kwh @ $0.14/kwh = $1940 annual credits. I also sized my system for a near $0 bill (at current rates, annual usage about $978, value of estimated annual production is $1035). 

MN net metering is somewhat different from yours in that if credits at the average retail rate ($0.108 currently with my utility) exceed usage, the utility pays us back the excess $ on request.

Since the utility pays us back the excess at the retail rate, my wife and I also are on a mission to further reduce our usage so that the payback also will cover some or all of our base charge of $14/mo.

What I'm having difficulty understanding is the DC to AC derate as applied to my system. My DC system is rated at 6.89kwh maximum output, the system microinverters are rated at system 6.5kwh DC nominal maximum input, and so far for year 1 the system is providing AC output at very close to 6.4kwh, which is a DC-AC derate of 0.93 based on the DC system or 0.98 based on the microinverter DC input. 

I'm guessing that the new panels may be performing somewhat better than on average they will perform after being in service for awhile. I will be interested in seeing your data as to whether the 0.77 derate may be somewhat excessive and you will experience higher than estimated AC output.

Keep the information coming!


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## woodgeek (Aug 21, 2014)

jebatty said:


> What I'm having difficulty understanding is the DC to AC derate as applied to my system. My DC system is rated at 6.89kwh maximum output, the system microinverters are rated at system 6.5kwh DC nominal maximum input, and so far for year 1 the system is providing AC output at very close to 6.4kwh, which is a DC-AC derate of 0.93 based on the DC system or 0.98 based on the microinverter DC input.
> 
> I'm guessing that the new panels may be performing somewhat better than on average they will perform after being in service for awhile. I will be interested in seeing your data as to whether the 0.77 derate may be somewhat excessive and you will experience higher than estimated AC output.
> 
> Keep the information coming!



According to this link,

http://davebuemi.com/2011/03/21/pv-system-derates-explained/

apparently the magic '0.77' includes many factors you haven't considered, including losses due to 'soiling', less than spec performance, wiring losses and system downtime (for repairs).  Seems intended more for a worse-case scenario over long periods of time, with unreliable inverters and underperforming panels.

It includes a 8% loss for the inverter. Does not include any downtime for snow.


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## peakbagger (Aug 21, 2014)

I think the derate factor was set intentionally conservative, few folks complain if the model underreports but most would complain mightily if it overestimates.

Panels used to degrade differently. When I got my first set of Sharp poly panels, they were intentionally down rated from the test value to cover initial degradation. When first put on line they definitely appeared to generate over rating and then gradually dropped  over the first few months.  

PV WATTS1 had one location in my state and it its quite a distance away and a completely different regional climate. I expect the derate also factors in the potential for model error due to a course data set.

The snow factor is big unknown. My roof mounted panels without raking may sit covered for 5 to 10 days after a snow storm with zero output. If I rake the lower edge, they normally would be clear in two days.


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## JP11 (Aug 21, 2014)

Curious how it all shakes out.  Guys doing install just said.. You're gonna be a BIG summer producer.

Inverter efficiency is pretty high with the transformer less design.

we'll see

like a kid at christmas... waiting for my login to see it working.  Im in Alabama at the moment.. hot and sunny here!


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## maple1 (Aug 21, 2014)

JP11 said:


> Maple.. I'm guessing your power is quite a bit cheaper than mine.  I had calculated payback at around 11 years.  The week after I sent in the deposit, PUC announced rates going up 4%.
> 
> I've got a spreadsheet going, and plan to put in production numbers, and let it extrapolate out and average to see where it crosses over.  I'm only 40.. and plan to stay in my house a good long while.
> 
> ...


 
My bills are right around $200 every 2 months. If I run our electric hot water heater in the summer, it gets close to $250. So say $100-125/mo. All-in cost is around 0.18/kwh.


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## jebatty (Aug 21, 2014)

> It [derate] includes a 8% loss for the inverter. Does not include any downtime for snow.


 The microinverters are rated at [correction] 96% efficiency. With my ground mount, snow clearing is easy, about 10 minutes of time with a long-handled broom, and I cleared snow regularly for the first winter, including at -30F outside temp. I have a little winter shading effective for about 5-6 weeks on each side of Dec 20, with my estimate being about a 4% derate (360 kwh) from annual production.

My panels are Suniva 265 watt and appear to be high performing compared to competitive panels used by others in my area. I also washed half my panels once this summer after the spring pollen season, and although there was a slight film on the panels not washed off by spring rains, I did not notice any change in per-panel output.

Time will tell as the years roll by.


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## JP11 (Aug 21, 2014)

When I asked the contractor about micro inverters instead.. he said I didn't have big shading issues, or really much of ANY shading issues.

He did say that 80% of their problems or service calls are micro inverter systems.  Don't know.. have no frame of reference other than what he told me.

remains to be seen how it all works.

JP


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## jebatty (Aug 21, 2014)

It will be interesting to see how are two systems compare over time. You're right, remains to be seen how it all works out.

Correction: The Aurora micoinverters are rated at 96% efficiency, not 98%.


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## JP11 (Aug 21, 2014)

Up and running on a cloudy day.  Real time monitoring every minute via internet or app


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## maple1 (Aug 21, 2014)

My mind is still boggled over power companies getting the 'over production' for free.


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## JP11 (Aug 21, 2014)

maple1 said:


> My mind is still boggled over power companies getting the 'over production' for free.



No, they don't.. not really.  You get one full year to use anything you produce.  So even if you over produced, it would take you a long time to have any credits 'expire'  you can always put a relatives bill in your name.. and send that second account the overage.

You always use up your oldest credits first.  Unless you grossly oversized your system, it should never be an issue.  Mine was sized around 95% of total bill.. then I added 6 more panels.  I need one more central air unit, and the wife's next car will be a plug in hybrid.

JP


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## maple1 (Aug 22, 2014)

Well, yes - I guess.

But it would seem, to me anyway, that there would be much more of an incentive to get people doing this, or get people who are doing it to put more panels in, if there was a plan for the power companies to buy excess production - even if it were at a rate discounted enough to allow them a small profit for re-selling it. And the more that do this, the better - I think that is not debateable. As I'm understanding, the only ones it is really worthwhile for, are ones with consumption on the high side - as the most you could hope for is to make your bill go to zero over the course of a year. I keep coming up with something like a 25 year payback for us (also realizing that rates will go nowhere but up in the future).

Now, if you could shift some other stuff that you are using other types of energy for, to electric, and generate for that too - that would shift the picture. Like a plug-in car, yes. I would dearly love to have one of those - if things progress enough that a reliable daily range of 200km is reached, in an affordable vehicle, and more quick charging stations get in place around here, I could see us in one of those. Our electric bill is maybe on the low side - our gasoline spending, maybe not so much. Even a plug-in hybrid is something I find myself thinking more about these days. Our Civic daily driver is 8 years old now & has almost 400,000 kms on it - it's pretty easy on gas but those kms would be even cheaper on electric. Then there's the SUV that burns twice as much gas per km - but it doesn't get driven near as much. When you live in the middle of nowhere, it's the price you have to pay if you want to be somewhere, I guess.


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## JP11 (Aug 22, 2014)

I guess the major difference in our payback timelines is the fact that I'll get 30% tax credit from the federal govt.  I can stomach a decade to get into the 'black'

started making power about 630am.  it's cloudy, so it's not making much.. but it's making 2424W at the moment.  847am


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## JP11 (Aug 22, 2014)

Cloudy day..  it's running just over 1/3 rated power.  Still an hour till noon.

Supposed to have some sunny days this weekend.


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## peakbagger (Aug 22, 2014)

Darn isnt it addictive when the meters run backwards? Enjoy it while it lasts, at some point the system becomes an appliance. Nothing wrong with that as it means the technology has matured. 

I do adjust my tilt angles on two of my arrays 4 times a year and If I am walking by my the meter I might take a look at it and on occasion I read the displays on the inverters but that is about it.


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## JP11 (Aug 22, 2014)

I haven't even been home to SEE it work.

I've asked my wife to read the 'out' meter 3 times in 24 hours.  

I can at least log on and see production in real time.  Once i get some data (a month in)  I'll start projecting break even.

I guess I can do the fun part now.. Go to my online banking and stop the 'auto pay'


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## CaptSpiff (Aug 23, 2014)

jebatty said:


> Minnesota net metering is somewhat different from yours in that if credits at the average retail rate ($0.108 currently with my utility) exceed usage, the utility pays us back the excess $ on request.


That's a smoke'in great deal. 
Last I researched, LIPA (Long Island NY) gives you credit against usage on a running year, then cashes you out at about 30 cents on the dollar if you have credits remaining each year. Sounds low until I looked at my rate of $0.22/hwr; about 50% is T&D charges, 40% is Energy, and 10% taxes & fees. Those taxes are low because there are NYS taxes hidden in the T&D and Energy portions. The conservation manager said it simply as "Why should we pay you more than we can buy it for ourselves?"
And we can't trade or transfer the credits either. They are locked to the billing address & account. That policy in Maine sounds nice.
The other thing we "sign over" to them as part of the LIPA rebate is the "energy credits" that are resold at statewide auction. I read on Hearth that a poster in NJ, PA or MA was getting several hundred $ a year for those (not sure their official name).


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## JP11 (Aug 23, 2014)

That's the difference as I see it too.  They don't BUY my energy.  They take it, and let me have it back later.  In essence, THEY are my battery.

If they were buying my power.. they would only pay the 'power' price, and not give me the money for 'delivery' that is more I think that the power itself costs.

JP


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## Where2 (Aug 23, 2014)

CaptSpiff said:


> The other thing we "sign over" to them as part of the LIPA rebate is the "energy credits" that are resold at statewide auction. I read on Hearth that a poster in NJ, PA or MA was getting several hundred $ a year for those (not sure their official name).



The proper term for those "credits" is SREC's (Solar Renewable Energy Credits or Solar Renewable Energy Certificates). Neither Florida nor Maine has a market for them, presently. My 4.4kW system would have generated 6 of them last year (1 SREC = 1MWh of renewable energy). They are worth ~$160 each in NJ at the moment. (if you search Google, there's a few sites that trade them like securities). I'll gladly accept a value of $0 per SREC in Florida, rather than buying energy at rates in MA, NJ or any of the states where SREC's appear to be marketable.

I believe another catch in the SREC system is that when you sell them, they may be considered taxable income to the seller. I don't need any more complications around April 15th. My PV system simply benefits the residents below it who invested in the new technology. Collecting 3kW at the moment, and using 0.42kW.


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## peakbagger (Aug 23, 2014)

Mass SRECs sell for $250 a MW (roughly) NH pays $50. I have my system enrolled and if lucky may get a check for $150 a year.


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## sloeffle (Aug 23, 2014)

maple1 said:


> Well, yes - I guess.
> Our Civic daily driver is 8 years old now & has almost 400,000 kms on it - it's pretty easy on gas but those kms would be even cheaper on electric. Then there's the SUV that burns twice as much gas per km - but it doesn't get driven near as much. When you live in the middle of nowhere, it's the price you have to pay if you want to be somewhere, I guess.



Man, I thought I drove a lot. I have 111k on 7 year old Honda CR-V.

Scott


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## JP11 (Aug 24, 2014)

Obviously.. some clouds and sun.  Still made over 45kw.  PVwatts says I should be making about 50 a day in Aug.  Still waiting for my first sunny day.

JP


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## CombatChris (Aug 25, 2014)

JP11 said:


> Obviously.. some clouds and sun.  Still made over 45kw.  PVwatts says I should be making about 50 a day in Aug.  Still waiting for my first sunny day.
> 
> JP
> 
> ...




Daaang and that's all the way up in ME. You're living the dream, man. I want a setup so badly down here in NC.... but you know, baby steps.

Get the land. The house. The barn. THEN the solar!


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## JP11 (Aug 25, 2014)

I had the land 4 years before I could build.  Had the house 6 years before I got the barn.

made almost 70kw yesterday.


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## Where2 (Aug 25, 2014)

CombatChris said:


> Daaang and that's all the way up in ME. You're living the dream, man. I want a setup so badly down here in NC.... but you know, baby steps. Get the land. The house. The barn. THEN the solar!


Had a portion of that debate with one of my co-workers today. He bought his wife a new vehicle over the weekend and keeps dreaming of having an EV some day. I told him an EV is an even better deal when PV refuels it. I reminded him that PV incentives expire in 2016.

I've been doing my research on installing my next little <5kW PV system in a place 1.8° latitude further north than JP11's house. Looks like it will work like a charm when it's not covered in snow...


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## JP11 (Aug 25, 2014)

Snow is the unknown.  They claim it will shed snow about the same as what the metal did.

Snow never hung around long on that dark brown roof.  Day or two after a storm at most.  We'll see.

JP


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## JP11 (Aug 30, 2014)

Had a 'perfect' no cloud day yesterday.  Just passed 500kwh in my first 10 days.

And had a buddy stop by with his drone this morning.  couple pics to share.


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## jebatty (Sep 1, 2014)

I vicariously enjoy your satisfaction with solar electric power. Remains for me a little magical to see the power without doing any work to obtain it, just flowing from the sun.

Your picture evidences some shading potential in late fall and winter, roughly 6 weeks or so on each side of December 20. Sun azimuth is down to 19 degrees at my location (47N), and trees quite distant provide shading on my system. My calculation is about a 4% maximum shading reduction from estimated annual production.


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## JP11 (Sep 1, 2014)

I've got a couple trees to knock down.  Gotta wait till I move the palleted up firewood, so I've got a good place to drop them.  The estimator got on the roof with this camera.  He took a picture of the southern sky.  It plotted on the picture the path of the sun each month.  The winter months it was pretty low, but he did say the few trees in the way would be leaf free by then.

We'll see

JP


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## Where2 (Sep 6, 2014)

jebatty said:


> I vicariously enjoy your satisfaction with solar electric power. Remains for me a little magical to see the power without doing any work to obtain it, just flowing from the sun.


Exactly. As others have said, in due time it simply becomes an appliance that works whether you are home or not. After a year, I've finally stopped checking mine daily to see how it's doing. It gets up and goes to work before I do, and although it only makes a dollar or two per day it does it without any fuss from me. I go about my business and it just works. 

As I was driving during the week and out paddling the kayak today, I found myself looking at different houses and barns and considering how well or poorly situated they would be for solar arrays.


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## JP11 (Sep 6, 2014)

Not a great day today. Lots of shade.  Still got 39.9kwh.  That's enough for my usage.  I've got a few hundred in the bank already (20 days in) and I'm just 70kw away from my first megawatt.   Not bad, will be my 17th day making power.  High water mark was 74kwh in a day.

JP


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## JP11 (Sep 16, 2014)

I'm 25 days in producing power.  Happen to be stuck in a hotel, so I pulled some data off the SMA website and crunched a few numbers.  Best day ever, still the 74kwh.  Had a real rainy day a few back.. only 9!  

According to PV watts, I should have made 50 a day last month and 48 this month.  I've made power 15 days this month, and 10 last month.  Average for that time is 54kwh per day.  

so.. i'm 10% above PV watts..  they say the panels degrade, so I think you can use the defaults on the website to get a pretty good idea.

JP


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## woodgeek (Sep 16, 2014)

Glad its working out, and that you are above trend, but your +10 over 2 mos is not significant.  IIRC PV arrays can show ±10% variation year to year because of weather fluctuations....kinda like heating and cooling loads.  We'll ask you again in 10 years.


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## JP11 (Sep 16, 2014)

I agree it's not statitstically relevant... but it's the only data I have at this moment.  My point was just to say that ASSUMING a bit of degradation, the PV watts website seems to be pretty accurate for production so far.

 My first meter read is in another week.  Looking forward to that bill for once!    I think I was already 'ahead' of my bill by 50 bucks on my budget plan.  I cancelled that, so I should be able to go with zero payment for a few months before winter hits.  We'll see how I keep up.  Last I looked,  my production was 400 above my usage.

JP


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## peakbagger (Sep 16, 2014)

A general comment is to expect a visit from the utility once or twice and possibly a meter swap out. Most utilities have antifraud software that flags changes in usage that doesn't seem to recognize solar. Thus your sudden decrease in power usage and net generation looks like you flipped the meter and thus fraud. It took the back office of my utility a couple of months to figure it out. I also got hand prepared power bills for several months as their software just didn't deal well with net metering. My bills also have a graph of average energy usage per day, that still isn't working.


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## jebatty (Sep 16, 2014)

PV is like solar magic. Do nothing and it pays you money. Makes sunny days extra special.


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## JP11 (Sep 16, 2014)

peakbagger said:


> A general comment is to expect a visit from the utility once or twice and possibly a meter swap out. Most utilities have antifraud software that flags changes in usage that doesn't seem to recognize solar. Thus your sudden decrease in power usage and net generation looks like you flipped the meter and thus fraud. It took the back office of my utility a couple of months to figure it out. I also got hand prepared power bills for several months as their software just didn't deal well with net metering. My bills also have a graph of average energy usage per day, that still isn't working.



I would be surprised if this happened.  They came out a few days before my install and put in a second meter.  I have two brand new meters.. both started at zero.  One is a 'buy' meter and the other a 'sell back'.

The 'buy' meter will run backwards (well, it's not the old style with a dial, but a digital representation of one)..  the meter will show running backwards, but it does not count down.  The 'sell back' meter will show the digital dial spinning and only count in the up direction as well.

Takes me a second looking at both to figure out what's going on.  I'm surprised when not much is going on in the house how little sun it takes to break even.

JP


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## jebatty (Sep 17, 2014)

My install got two digital meters also which operate like yours do, plus the installer put in a third mechanical production meter to verify PV production at the panel as opposed to the software reported production, and also to verify that the buy back the utility is giving me is accurate. The buy back/sell has been right on. Panel production is reading about 1% less than software reported production. That might be line loss over the 280' between my PV and the panel.

Determining actual house electric use is: buy meter + production meter - sell meter.


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## JP11 (Sep 17, 2014)

Took a look this morning.  my sell meter is 500 ahead of my buy.  not bad for being a week shy of a month.


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## JP11 (Sep 28, 2014)

5 weeks in to get over 2 Megs.  Pretty cool.  Sell back is over double what I've purchased.  Had all the AC running, and wife was shooting pics (she's a pro photographer with LOTS of lights )   Meter was still running in the 'good' direction with full sun. 

JP


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## JP11 (Mar 18, 2015)

Well, PV watts does (30 year AVERAGE weather)  This year's snow and cold sure hasn't been average.

My one inverter has been sporadically making power for two months, but the other was not (4 foot snow drift)

Today, my guess (I'm away on a trip) is that the second 24 panels are exposed enough that the second inverter 'woke up'

It filled in all the past data.  My low point.. Feb I was supposed to make 10370 watts. I made 618

I had massive, weeks long outages.

I got messing with my spreadsheet that I paste in outputs.  If I cull out the partial months.. I'm at about 68% of PVwatts estimate for production.  We'll see how it does when the rest of the snow is gone.

JP


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## JP11 (Mar 29, 2015)

Best day ever today (only had system online since Aug 22)

75kwh and still going.  

Day's get longer for the next three months almost.  I guess this is where I'm supposed to bank a bunch of power for next winter.  I changed 4 circulators on my wood boiler to 'bumblebees'  they save a ton of electricity.  All future power bills should be under 10 bucks!

JP


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## jebatty (Mar 30, 2015)

Congratulations again! PV stimulates the immune system to hunt out and kill every electric energy wasting device and to trim all others to the minimum that's needed while on the way to electric net zero.

March is headed towards a very strong finish for my 6.5kw system. Absent something unusual, I should end the month very close to 1MW and above the PVWatts average for March. Two days to go.


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## JP11 (Mar 30, 2015)

My next benchmark.. the day I make 100kwh.  I'm pretty sure I can do it closer to June.

JP


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## JP11 (Apr 5, 2015)

Easter started out snowy.. but I'm going to get 72 kWh for the day.  Can't complain about that.  April production has already surpassed Jan and Feb combined.  Few more days, I'll have March's total beat too.


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## begreen (Apr 6, 2015)

Very nice. Looks like you're clipping at 10KW. Is this the limit of the inverter?


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## JP11 (Apr 6, 2015)

Yes.. two 5k inverters.  They seem to run about 5060w as a max.

Panels aren't even a year old yet.  I suspect that I'm clipping by a couple hundred watts during the peak of the day.  So I'm losing a bit, but I bet the panels 'wear' into the inverters and it works about right.

JP


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## jebatty (Apr 7, 2015)

Regarding clipping, clouds and shading: if you have a good morning production with a mostly smooth curve until clipping starts, and a similar afternoon not too far in time before or after the morning, you can overlay the two curves and "round out" the resulting curve. Then if you can get a kw data download for those periods, insert data points to fill the curve, you can determine quite closely the impact of clipping, clouds and shading vs a full sun day, and similarly you can determine what likely maximum production could be at the time of the year when you would do this.

I have micro-inverters rated at 250w, each panel is rated at 265w watts maximum, and for my 26 panels based on the inverters that comes to 6.5kw rated, based on the panels 6.89kw maximum. I have in fact observed maximum inverter output at 268w briefly, and if that continues more than a short time clipping occurs at about 265-266w output, and that's a quite uncommon event for me. The additional 20 panels I am having installed will use the same micro-inverters and have a panel rating of 270w maximum, and I suspect I will see a bit more clipping, but it still will not result in a significant loss of power which would make it worth buying higher rated inverters.


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## JP11 (Apr 7, 2015)

I have seen a few days that were near perfect.  Maybe someday I'll print out the graph.  It's a very smooth curve.. I could easily find out what I'm losing.  I guess my question would be.. what then?

The installation company didn't even offer me 6k inverters.  Maybe it's diminishing returns.  As I said, I suspect the panels will come down a bit with age.

JP


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## begreen (Apr 10, 2015)

We're currently starting to see clipping at 4.5KW. That is a bonus considering our inverter is rated at 4.2KW. This is why I put one array on a pole. I will be rotating it 45 deg to the southwest soon. Theoretically that will reduce the clipping period and extend solar gains later into the evening.


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## JP11 (Apr 10, 2015)

I have heard that you can 'over clock' them and run them higher.  I just don't know enough about the inverter.  I guess since it's under warranty... and it's LOTS of DC volts.. I won't be messing with it.

JP


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## JP11 (Apr 15, 2015)

New record today..  And the days are only getting longer.  81kwh


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## jebatty (Apr 16, 2015)

For our equally sized systems, same maximum power output so far. I too had 80.94kwh on Aprill 11. Had an odd problem yesterday. There was a brief power outage and when power came back on one of my two micro-inverter data recorders stopped reporting to the website. After a lengthy, but very helpful, discussion with tech support, and several different approaches from rebooting to reprogramming, the solution ended up being removing and reinserting the small coin cell  battery internal in the data recorder. The battery voltage tested fine, must just have been slight corrosion on the contact.


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## JP11 (Apr 16, 2015)

Every once in a while my data drops out.  I've had it go as long as a couple days.  It has always gone back and filled in the missing information. It even went back a month and a half after being snowed out.  I'm surprised for something internet connected how slow it is to update.  I happened to be in the barn with my dad yesterday, and saw I had made 40kw.  When I went back inside.. the display was running over half an hour behind.  It matches perfectly by days end.


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## JP11 (May 1, 2015)

Right on the money for what PVwatts said.  Got my first minimum power bill.  10.65  I hope and expect it to stay like that forever now.  Last month's bill was buy 505kw, and sell back 1100.  It's nice to see after a rough winter.  I was WAY under on production.


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## maple1 (May 1, 2015)

I keep thinking out a solar setup & where I might put one if I wanted - I really think small solar has a lot of merit - but keep coming back to the issue that, simply speaking, my annual returns would be limited to my annual consumption. Which is around $1000/yr. So I am still limiting myself to just thinking about it - but haven't completely ruled it out as you never know what the future might bring. Nice to see your success with it though.


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## JP11 (May 1, 2015)

Maple.. It's VERY dependent on what your local utility rules are.  If they don't provide 'net metering' that's advantageous.. you just can't win.  Essentially, the neighbors get my power, and the power company functions as my battery.  If you aren't paid retail rate for your excess production, your time to pay back the system is VERY long.

I did it because I wanted to.. and I know it will EVENTUALLY pay a nice dividend in power for free.  At the current moment.. my payback is at 13 years.  I suspect those numbers to get closer to 10.5 or 11 years, I'm just working with assumptions for some of the year, and a VERY unique winter snow drift this winter.

JP


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## tmarch (May 6, 2015)

I used $ from my retirement IRA to pay for my 6K system and it's ROI is a LOT more than the balance of the IRA.  I was able to use the $ without paying taxes due to the 30% tax credit. 
My utility pays me their wholesale rate for the excess I produce which isn't good, but at least they allow me to use them for a battery. 
Lots of ways to fund a system, just takes some planning.


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## JP11 (May 6, 2015)

Ouch.. sell back at wholesale.  That helps make the case for batteries.  But there isn't a battery system out there that will let me use power in the winter, that I made in the summer.   If my terms had been that way, I likely wouldn't have done the system.  It's so very seasonal for me.  The first 5 days in May have produced more power than all of Jan and Feb combined.

JP


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## JP11 (Jun 1, 2015)

Made 108% of what PVwatts said for May
	

		
			
		

		
	




	

		
			
		

		
	
 .  my monthly billing cycle doesn't quite match up with the calendar.  I bought 425kwh from the utility. Sold back over 1200.  Will come in handy come winter.  I installed a new central air system in the house, so that's going to up my usage.


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