Solar production. Panel ratings/claim vs reality

[MAX-24-Dean]

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?

December and January output is about 25% of system total here.
February and November are about 46%.
March, October are about 83 %.
April, September are about 90%
May, June, July, and August are about 99% production months.
Latitude 46N
Unique conditions here in that I live in a box canyon with a hill that has 300 foot higher elevation in the sunrise direction and a 200 foot mountain to the west (sunset). This has quite a negative effect on my December and January production.
Panels are at 37 degrees, reason being the cost benefit ratio of the extra cost for a foundation at a greater angle would not pencil out for the small solar production gain with the higher angle. Basically you have to account for solar panels being sails that catch the wind. So the higher the angle placement for the panels the more you have to spend on the foundation (ballast of a sail boat) to overcome the forces of the wind.
My new location had to account for 100 lb snow load per square foot and the 100 lb wind loading.
PVWatts is very accurate for production potential for any location, you can rely on the numbers with a few exceptions. One local condition for an installtion was fog. For about 3 months each year during the winter the location is fogged in until the later part of the day. Take everything into account and write it down so you can review it and make a good decsion based on the knowledge for your location.

 

[MAX-24-Dean]

The company at the link has regular sales events throughout the year.
Currently 6% off sale for the 4th of July.
I have used thier services for more than 15 years and I would reccommend the free consultation they provide.

NAZ Solar Electric | Off Grid & Grid-Tied Solar Power Systems

Solar power equipment for homes, businesses boats and RVs. Backed by industry experts ready to help get your solar system up and running.

www.solar-electric.com

 

[techman]

If you have 10KW of panels, you will never produce 10 KW. The standard ratings are at 1 kw/m^2 illumination. So unless you live on the equator and it is high noon, you will never see the rated output. I have a 9.2 KW rated system on a ground array, located in PA at 40.4N I average 1+ MWH per month in the peak months and as low as 550 KWH per month in the winter. Annually I generate around 11.5~12 MWH for the year. That covers about 40% of my total usage.

A typical day looks like:

The dips are passing clouds, and you can see the start, peak and tail off in the late afternoon.

Paul

 

[LD1]

If you have 10KW of panels, you will never produce 10 KW. The standard ratings are at 1 kw/m^2 illumination. So unless you live on the equator and it is high noon, you will never see the rated output. I have a 9.2 KW rated system on a ground array, located in PA at 40.4N I average 1+ MWH per month in the peak months and as low as 550 KWH per month in the winter. Annually I generate around 11.5~12 MWH for the year. That covers about 40% of my total usage.

A typical day looks like:
View attachment 878454

The dips are passing clouds, and you can see the start, peak and tail off in the late afternoon.

Paul

Good info.

I think 10kw is what I am gonna need and based on your data....the PVwatts calculator and numbers I showed seem pretty realistic expectations

 

[LD1]

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

Oversizing dont help me. It actually hurts the ROI because even going over a 10kw system...there isnt much dropping in price in terms of cost per kw

Its all my rural coop electric company.

Basically as long as I dont produce more than I use in a given month, every kwh I can make will save me 12.5 cents.

IF I make more than I consume in a given month....anything over what I use is only saving me 7.5cents.

So no benefit to going too big as it will delay the payback. And still never gonna take the bill off the table because we have a $57 meter charge.

Only way to wipe that clean would be to produce 760kwh MORE than I use every month. Id need a system that could make ~2200kwh in the summer. Pushing a 18kw array. Then that system is only gonna make ~1200 kwh per month in the winter and ID still have a ~900kwh bill and the $57 meter charge. So I'd still be paying ~$170 for about 3 months out of the year.

But I dont think they will allow oversizing that much anyway.

Given the net metering policy as I have already explained....the sweet spot is to never make more than I use. That way I know for certain that every kwh I make directly saves me 12.5cents rather than 7.5 cents

 

[newbury]

Given the net metering policy as I have already explained

But didn't that policy just change?
What guarantee is there it won't change again?

 

[LD1]

But didn't that policy just change?
What guarantee is there it won't change again?

Yes It recently changed for the better.

Who knows if it will change again. I can't make a decision based on speculation about what may or may not happen in the future

 

[ning]

December & January suck.

I'm at approximately 39°N.

Here's 2023.

On a dark day there's very little production.
I have a small amount of production clipping because the system is fairly new so the panels can produce slightly more power than the microinverters can handle. The math was something like bigger microinverters would've cost another $1000+ and the clipping is likely worth about $200 over 20 years.

 

[LD1]

Still in research mode at the moment looking at the various options for inverters, mounts, and panels.

I think I am leaning towards the hoymiles HMS2000 inverters. They are a 4-into-1 but still have individual panel optimization....and a fraction of the cost of a complete enphase system. And looks like they can handle the output from some of the larger panels better than anything enphase has either.

Also been looking into Aptos and APsystems....both have a 2:1 inverter but currently leaning toward the hoymiles....and read some good things.

Basically I can get enough inverter/cabling/connectors/DTU, etc to do 20 panels for about $3000 or 24 panels at about $3300. Which only leaves buying panels and mounting.

NAZ has a 9.6kw kit that actually has 6x of the hoymiles inverters. Its a $9000 kit but I dont like the choice of REC400w panels at a price of $225ea when I see so many other panels (including bifacials) at far cheaper cost per watt. So I basically selected everything included in that kit minus the panels to come up with those above prices.

As for mounting....I am leaning currently toward the EG4 mount. For $279 to mount 4 panels....and 25-30-35 degree adjustable....looks hard to beat. All I need is the concrete footing or piers....which I can easily handle.

For panels, I can find 400w bifacials for ~$130 per panel and 545w bifacials for ~$200 per panel.

So....for a 10kw system....and keeping things in multiples of 4 (to work both with the racking and the 4-to-1 inverters.....

6 EG4 mounts..................$1674
24 panels @$130..............$3120
inverters and cabling.........$3340
Total................................$8134 for 9.6kw

OR

5 EG4 mounts..................$1395
20 panels @$200..............$4000
Inverters and cabling.........$2964
TOTAL.............................$8359 for 10.9kw

Obviously will have more in it than that with having to run power from the array to house, and concrete footings, and some other odds and ends. But I am thinking I can get this done for ~$10k

The question....and waiting on some follow up emails to different companies....is how well the hoymiles work with the 545 watt panels and/or if I will experience any clipping or want to overheat the inverters or anything. Even though the components for going with the second option and 20 x 545w panels is a few hundred $$$ more, its one less rack to mount (less concrete)....a little less wiring....and about 1.3kw larger system. So total cost will probably be the same for a little larger system.

As much as everyone raves about enphase....they are just too dang expensive and pushes the ROI out too far for my liking given the alternatives out there. And they dont handle the larger panels. So 24 micro inverters, their combiner/monitering stuff, cabling.....Im at nearly $7k for just enphase stuff. About $4000 more than hoymiles.

Again, still just penciling out and researching what is out there to find the most cost effective way to get to 10kw. But things are looking good and this may become a reality sooner rather than later.

 

[tradosaurus]

If you're not getting the solar panels and installation for free you have to factor in that cost.
We looked at solar and minimum cost would be about $30K which would buy a LOT of electricity over the years.
Most solar companies, IMO, are scammers.

 

[Carl_NH]

Hi LD,

December 2014 Installed 24 LG Mono Panels 300 W with Solar Edge inverters for 7,2KW
Garage Roof Mount – 38* angle, 190* south facing, Latitude 42*
Cost installed $26K, State credit $4000 Federal Credit $8500 net cost $13,500
ROI was 8.5 years – electric cost .18 KWH when we installed then rose to .22 then to .33 last year. We are grandfathered into true net metering where they pay us for excess at the same price we pay for electricity so if we over generate they send us a check that month.
Annual use – 10-11,000 KWH vs annual generation 8100-8600 KWH average
Q1 – 15-1800 KWH
Q2 2700 KWN
Q3 2600 KWH
Q4 15-1800 KWH
The lowest generation months are December, January and February mostly due to sun angle and snow, but they shed snow pretty fast.

I like your idea for doing the tilting ground mount, and really I think you need to keep it simple with one adjustment for summer and one for winter – makes it easier?
Also you should factor in some increase in electricity rates – they never go down, and then the cost for delivery (poles lines etc) is going up everywhere.

 

[LD1]

If you're not getting the solar panels and installation for free you have to factor in that cost.
We looked at solar and minimum cost would be about $30K which would buy a LOT of electricity over the years.
Most solar companies, IMO, are scammers.

I did factor the cost of the panels. I gave the prices I could find for both the 545w bifacials and 400w bifacials.

I plan on installing myself

 

[Carl_NH]

Here is a view by month and in 2021 we took down a lot of pine trees and this increased the production by nearly 1000KWH per year.

Also for your install do you have shading - if you don't then the per panel optimizers aren't that necessary. Then on system sizing - I think 6 arrays vs the 5 would be perfect getting you close to 12KW.

Then on the installation - the tax credit applies to the installation too - so if you have $5K in electricians and other costs and your time say its 40 hours at $80/hour should be part of the "costs" for the rebate.

 

[LD1]

I like your idea for doing the tilting ground mount, and really I think you need to keep it simple with one adjustment for summer and one for winter – makes it easier?
Also you should factor in some increase in electricity rates – they never go down, and then the cost for delivery (poles lines etc) is going up everywhere.

The EG4 mount is only adjustable from 25,30,35. And using PVwatts calculator....it actually shows 25 is the best for the april-august then sept through march shows 35. I would have though 30 would have been better for awhile...in september and maybe march. But their calculator doesnt show that to be the case.

But it wouldnt be hard to simply set to 35 laborday, and back to 25 every easter. Easy and simple.

Factoring in the cost rise of electricity is the unknown variable. And no one can accuratly predict the future.

I have electric bills that date back to 2006 where we were paying ~8 cents per kwh......I also have bills from 2018-2019 also showing 8 cents. It wasnt until covid that we rose a little to where we are now which is ~12-12.5 cents.

So when I frst looked at solar and everyone cited the same thing....rising energy costs.....that wouldnt have panned out as our rates didnt increase for about 12-13 years. But what has changed is system/panel prices have came down, and inverter tech has gotten better, and now bifacial panels.....

So yes, while I do know that electric costs will "likely" go up......I couldnt use that logic to justify back when the best ROI I could pencil out was 17-20 years even with the FED rebate.

And about every 2-3 years I have a renewed interest in solar that makes me look into it. And every time in the past I have not been able to even get under 15 years....and alot of that was the net-metering policies (or lack of) for my local electric company.

But the combination of them making some changes to their net metering in favor of solar, and panel prices dropping drastically, and some new players in the inverter space to compete with enphase and the other big names.....now has a payback that looks like I can get under 10 years. So now I have started to get serious about shopping, pricing, and asking questions.

Obviously the ground mount is an added cost. Sure, roof mounts are easier and cheaper....but I have a north-south ridgeline. Almost perfectly north and south....just a couple degrees off. And I have some large trees shading pretty much the whole roof from 1pm to dark. But even if I had an ideal roof....I still dont like the idea of a roof mount, penetrations, less than ideal angle, fixed angle, etc.

 

[tradosaurus]

I did factor the cost of the panels. I gave the prices I could find for both the 545w bifacials and 400w bifacials.

I plan on installing myself

What are the cost of your panels and controls?

 

[LD1]

What are the cost of your panels and controls?

Its all in post #29. The two routes I am considering.

There seems to be many options for panels at ~$0.30 per watt

 

[nyone]

OP I think you should try to lower your 2200kw a month useage before you go solar.

 

[Carl_NH]

I agree with reduction of usage as well - insulation, more efficient heat/air conditioning etc.

As far as the original question about the longevity and loss of efficiency over time, our LG Panels have been installed nearly 10 years and they are as efficient today as when new - LG claims like 2^ annual potential reduction but we haven't noticed much of a change in 10 years.

 

[MAX-24-Dean]

Panel efficiency in the heat and panel degradation per year are factors to look at.
It all depends on what your goals are with your system.
The REC panels you mentioned have a degradation rate of.25% per year and are still producing 92% of original output after 25 years. (I install these or reccomend equivalant specifications to them)
The less expensive panels have a degradation rate of .40% to .50% per year and will be producing 80% to 84% after 25 years.

The temperature coefficient on the data sheet will determine the reduced output as it gets hotter. Something you might want to look at if the weather is hot for extended time periods.

All this being said, it is not as important as it used to be as the price per watt of the less expensive panels justifies adding a panel or two to make up for these losses.

 

[Carl_NH]

Max 24 - yes this is what I recall now 10 years later .25% per year - I thought it was 2% but as mentioned in 10 years we have not seen any appreciable drop of generation with the LG 300 Mono panels. These panels were the best you could buy in 2014 and also you are correct if you buy a lower cost panel with a .4 or ,5% per year, just add 2 or 3 more panels.

I wish I had installed 10KW instead of 7.2 KW ($32K vs 26K at the time) as I got a quote in 2020 to increase to 10KW - a new inverter, and 6 panels was $15K - a no go - and if we installed 10KW initially it would have cost $6K more. Hindsight is 20-20, shoulda bought once and been done with it.