Solar production. Panel ratings/claim vs reality

[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.