Help with large solar installation estimate

[CHGolferJim]

I was thinking physical depreciation.......should have used another word. Thanks.

 

[Saghost]

I was thinking physical depreciation.......should have used another word. Thanks.

Okay, but I'm still not understanding your point here. How is the reduced future value of the panels relevant to the payback period, since that period is defined based on the assumption that you are getting every dollar out into the construction back eventually?

Or maybe you meant physical degradation - los of generating capacity over time? It's not clear how much of that happens in reality on modern panels, but the warranties guarantee 80% of capacity after 25 years on nearly all solar panels, so any effect would be fairly small.

 

[tomas]

PLEASE READ - regarding flat roof -

1) You do NOT want to penetrate roof to mount racking, so you will want to use ballast system. That means the racks are held down with cinder blocks. Make sure you inquire with your local permitting organization to see what their ballast requirements are and what they use as engineering standard. I recently did ballast system in Chicago. They adopted a new California Board of Engineers standard which resulted in absurd amounts of ballast. I could wax poetic on this forever, but to be compliant, you may have a lot of weight up there, and may need to check your roof construction to make sure it can support the weight. This may be a limitation regarding how many panels you can put up.

2) You do NOT want to panel the whole roof. There's a bunch of stuff up there that needs maintenance (chillers, vents, etc.), and you need to leave sufficient space to get to it.

3) Condition of the roof is very important. If you have to lay out a new roof in 7 years, someone will have to disassemble/reassemble the panels, racking, and ballast. This is relatively easy and should not cost a ton if you have left ample space to stack stuff while roof repairs are going on. If not, you could significantly increase the cost of future roof replacement. On the plus side, panels typically extend the life of the roof below them, so maybe you will get more time than current expectations.

I think, given what you are thinking of doing, you'd probably be wise to get a reputable installer or 2 up there to take a look so you have a clear idea of how they'd install, how you'd remove for maintenance, and how many panels you could fit. They all want business, so I would expect a site survey to be free.

 

[Robert.Boston]

It's also worth talking to your utility. I believe you're in the SCE service territory? Unrelated to PV, SCE offers a no-cost program to improve energy efficiency in multifamily buildings like yours, which might be worth exploring.

Our Multifamily Energy-Efficiency Program offers no-cost energy-saving products including qualified lighting, pool pumps, window evaporative coolers, faucet aerators and low flow shower heads through SCE-authorized contractors.

SCE used to pay for a part of solar installs on multifamily housing through its MASH program, but they filled up their quota last year.

SCE uses a net metering program, which is very advantageous for solar. The details are HERE.

This project will be more complicated if each unit is separately metered, but I'm sure it's not an obstacle.

 

[CHGolferJim]

Okay, but I'm still not understanding your point here. How is the reduced future value of the panels relevant to the payback period, since that period is defined based on the assumption that you are getting every dollar out into the construction back eventually?

Was thinking payback would be based on cost of solar kit and running expenses vs. purchasing electricity from the utility. Are running expenses really low? #noteducatedonsolarinnc

 

[Robert.Boston]

I was thinking physical depreciation.......should have used another word. Thanks.

There is a very slight degradation over time of the panels themselves. According to a 2012 study by NREL:

Nearly 2000 degradation rates, measured on individual modules orentire systems, have been assembled from the literature, showing a median value of 0.5%/year.

The sample set seems skewed towards pre-2000 installations, and they don't have much info on thin-film panels. In any case, the physical depreciation/degradation seems almost negligible.

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Was thinking payback would be based on cost of solar kit and running expenses vs. purchasing electricity from the utility. Are running expenses really low? #noteducatedonsolarinnc

The actual running expense is zero in most months, particularly in a place like NC that gets enough rain to keep the panels clean. The 'running costs' are all about replacement of items:

• Panels: can be physically damaged by winds, hail, falling objects, or have internal wiring issues
• Inverters: like any power electronics, these can fail and need replacement
• Roof: the presence of solar panels adds expenses to any roofing replacement you'll eventually need to do. If you accelerate roof replacement so that you start with a fresh roof when you put up the PV (a good idea), then the lost useful life of the roof should be charged to the project's economics.

 

[CHGolferJim]

Thank you for taking the time, Robert. It's time to carefully assess solar installation for my house. A very quick visit to solarpowerrocks.com suggests (with their probably optimistic assumptions) a 6-year payback in NC on a 5kW system at pre-rebate cost of $20k, excluding a $13k increase in home value. If all that is true, it's a no brainer.

 

[gjunky]

All,
Hopefully one of you can help me out with a very rough order of magnitude estimate for our condominium complex. Here is the story: We had looked into solar panels several years back (~5-6) when I was not on the HOA board. The answer back then was that it was not cost effective. Since then our rates have increased (surprise!) and panel costs have dropped significantly. We just did a building remodeling project that cost about $120,000. It's a 50 unit building. And we do a remodel about every 10-15 years depending on how things wear and who is controlling the money.

Eventually I will be the HOA President again, and I want to get solar panels put onto the building. I would like to send an e-mail out to the board and some residents who are very pro solar power to let them know either: 1) What $120,000 can do with respect to putting a system in, and how much we would save monthly, or 2) If our system would cost less than $120,000, how much would it cost to offset all our power consumption? It seems like a good time to get people thinking about how it might be a good idea to invest some money in something that will pay monthly dividends versus cosmetic things.

Here are the monthly details for both July and December so you can get an idea how much power and cost we are talking about:
July: Kwh/Day was 166 (5,146 total Kwh), and the power bill was $970 ($0.188 per Kwh)
December: Kwh/Day was 199 (6,169 total Kwh), and the power bill was $1,140 ($0.185 per Kwh)

Building is in zip code 91101. I'm really curious to see what our system payback time would be now.

Thanks in advance,
RT

I am not trying to just give you a short useless answer but I think it would be worth it to call someone like SolarCity and have them give you the numbers. That way there is no guess work. Now that I have had their system for over a year, I can compare what they predicted with what my system produced and I am happily surprised that it over produced (planned was 14.5mWh and produced was just over 16). Since I am waiting for the X, I already over sized it a bit as the extra power will be used for the car.

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