Questions on Proposal Comparison

[fordmantpw]

Hello all! We have been doing research and getting proposals in preparation for a PV solar system for our home. First, some background. The panels will go on our detached garage, with a roof facing nearly due south (170 degrees). When we built the garage, we built with solar in mind, so the breaker panel and roof structure for the building were built so that no changes would be necessary (225 amp panel with 200 A main breaker, heavier wiring to meter panel, stronger trusses, etc.). We are located in central Missouri. We are looking for a system to replace 90-100% of our electricity usage, which is currently about 1500 kWh/month, so we need about a 12.4 kW system to meet those goals. Below are some proposals that we have received, and I wanted to ask the experts here for advice on equipment costs, and whether there is an advantage to go with one over the other based on equipment. Prices range from a low of $2.67/W to $2.98/W (well, there was one for $3.78/W that I threw out already). We don't typically just go with the lowest cost option as we are 'value for your dollar' type of people, and not 'lowest-buck'. We typically do a lot of research, reading reviews, etc., and go with what we feel will give us the best service and stay within our budget. That is why I came here for help...I wanted to get thoughts on the equipment and whether one was better than another. With that said, here are the options we are looking at.

System	Company	Size (kW)	Price/Watt	Total Cost	Workmanship / Labor Warranty	Panel Watts (#)	Panel Brand	Inverter	Optimizer
1	A	13.780	$2.88	$39,651	12 years	265 W (52)	Jinko	Fronius	On Panel
2	B	12.180	$2.69	$32,750	1 year	290 W (42)	SolarWorld	SolarEdge	SolarEdge
3	B	11.760	$2.67	$31,400	1 year	280 W (42)	REC	SolarEdge	SolarEdge
4	C	11.970	$2.69	$32,250	5 years	285 W (42)	Suniva	Enphase Micro	N/A
5	D	10.440	$2.92	$30,494	10 years	290 W (36)	SolarWorld	SolarEdge	SolarEdge
6	D	11,700	$2.98	$34,919	10 years	325 W (36)	Panasonic (15 year wty)	SolarEdge	SolarEdge

Company A is a rather large company, started in MO, but branching out across the country. Company B is a really small company, with really only one employee, but others help with install. Companies C & D are medium-sized companies, with company D being one that I have communicated with quite a bit over the past 3 years as we built our home and detached garage, working with them to make sure we had our bases covered for solar. Also, the gentlemen that owns company D is extremely personable, and has said that he will stand by his work, even if something were to happen to his company. I mentioned all that to throw that into the mix to get your thoughts on company size and service.

So, after all that, any advice or thoughts on each system would be helpful. Thanks for your time and help!

[huge]

I'm not an expert, but I would probably go with D. If he's put so much time into it for you already, that's worth a lot. Price is good enough, good components and seems like he will give you a good installation

[J.P.M.]

Somewhat in the spirit of your last sentence, and aside from what looks like first costs, which in your market I'm ignorant of, several things come to mind that you have not mentioned but are some of what many folks think are good design parameters and considerations perhaps worthy of some thought to before getting quotes:

Roof slope ?
Panel layout: Accessibility for service/cleaning ?
Did you estimate output on your own using something like PVWatts to verify vendor estimates ?
String or micro inverters ?
Was the cost of the system with respect to the long term net worth of the estimated savings produced considered ?
Assuming this is to be a grid tie system, were the possible scenarios of future utility prices and possible future changes to net metering rules considered ?. That is, is cost effectiveness a consideration ?
If long term cost effectiveness is a consideration, have the more cost effective and generally more environmentally benign measures of use reduction and conservation measures been considered ?

NOMB, and maybe you've already done all of the above and more, or such things are not a priority for you, but it looks like the cart's before the horse just now.

As part of your research, have you read "Solar Power Your Home for Dummies" yet ? A free net download, or an updated version for ~~ $25 or so. Knowledge is power.

After making sure the equipment is of decent quality, and speaking to your request for info on equipment quality, which, while still a big consideration but somewhat less of a chore now that panels and to some extent inverters are or have become a commodity, the quality, integrity and experience of the installer is your next biggest consideration in the quest for most bang for the buck. The panels will probably outlast your stay in the house. A good vendor and the quality they can bring to a job (but not guarantee BTW is worth a premium. How much ? Your call. Negotiate tough but fair.

BTW: forget the smiles and "comfort factors". This is business. A lot of unprofessional peddlers will smile. Read the book, and at initial vendor contacts, ask vendors questions you already know the answers to. You'll probably find you know as much or more than some vendors. You'll quickly separate the wheat from the chaff.

With panel longevity in mind, make sure the roof under the array will last as long as the panels, although over a garage is not the most disastrous place for leak.

Take what you want of the above. Scrap the rest.

Welcome to the neighborhood.

[ButchDeal]

personally I would stay away form the fronius/Tigo solution form company A.
If there is room to fit 13.78kw of 265W modules, have you thought of trying 275W QCell? maybe from company D

[fordmantpw]

I'm not an expert, but I would probably go with D. If he's put so much time into it for you already, that's worth a lot. Price is good enough, good components and seems like he will give you a good installation

Those are my thoughts as well, but wanted to get other input to make sure I'm not off base.

I put my answers inline below...

Somewhat in the spirit of your last sentence, and aside from what looks like first costs, which in your market I'm ignorant of, several things come to mind that you have not mentioned but are some of what many folks think are good design parameters and considerations perhaps worthy of some thought to before getting quotes:

Roof slope ? 5/12, decided on after initial planning for solar.
Panel layout: Accessibility for service/cleaning ? That is one of my concerns with option #1...how they are fitting all of them on the roof. The others have definitely taken that into account as they mentioned it in their proposal.
Did you estimate output on your own using something like PVWatts to verify vendor estimates ? Yes, everything checks out really close. Seems they all use the same software as PVWatts.
String or micro inverters ? Noted in the table. All are string with the exception of the Enphase micro
Was the cost of the system with respect to the long term net worth of the estimated savings produced considered ? I have all of that in the proposals, but left it out. They are all different as they use different estimates for future electricity costs, but in the end, it all looks OK on paper.
Assuming this is to be a grid tie system, were the possible scenarios of future utility prices and possible future changes to net metering rules considered ?. That is, is cost effectiveness a consideration ? Yes.
If long term cost effectiveness is a consideration, have the more cost effective and generally more environmentally benign measures of use reduction and conservation measures been considered ? Yes. We took all that into consideration when we built our home. LED lights, geothermal, etc.

NOMB, and maybe you've already done all of the above and more, or such things are not a priority for you, but it looks like the cart's before the horse just now. No cart before the horse, I just really didn't have questions in those areas.

As part of your research, have you read "Solar Power Your Home for Dummies" yet ? A free net download, or an updated version for ~~ $25 or so. Knowledge is power. I have not read that yet, but I will. Thanks for the suggestion.

After making sure the equipment is of decent quality, and speaking to your request for info on equipment quality, which, while still a big consideration but somewhat less of a chore now that panels and to some extent inverters are or have become a commodity, the quality, integrity and experience of the installer is your next biggest consideration in the quest for most bang for the buck. The panels will probably outlast your stay in the house (not likely...we plan to be here forever. We just built our home on our tract of land and have no plans to move). A good vendor and the quality they can bring to a job (but not guarantee BTW is worth a premium. How much ? Your call. Negotiate tough but fair.

BTW: forget the smiles and "comfort factors". This is business. A lot of unprofessional peddlers will smile. Read the book, and at initial vendor contacts, ask vendors questions you already know the answers to. You'll probably find you know as much or more than some vendors. You'll quickly separate the wheat from the chaff. I actually did that, and all vendors (with the exception of the one I threw out) were very knowledgeable and I had a high comfort level with them all. I have an electrical engineering degree, so have a decent amount of knowledge in this area myself.

With panel longevity in mind, make sure the roof under the array will last as long as the panels, although over a garage is not the most disastrous place for leak. Roof is a metal roof, and I have no concerns about longevity there.

Take what you want of the above. Scrap the rest.

Welcome to the neighborhood.

Thanks for the help!

[fordmantpw]

personally I would stay away form the fronius/Tigo solution form company A.

Good to know.

If there is room to fit 13.78kw of 265W modules, have you thought of trying 275W QCell? maybe from company D

No, I haven't brought up anything specific as far as panels, just having the contractors make their proposal for what's best. I can contact them and ask, but company D is ensuring proper set-backs for code and room to work around the array on the roof. I don't think company A has done that, otherwise they couldn't fit 52 panels on the roof. The roof is 21'-8" x 44'.

[ButchDeal]

that makes since. stick with the higher performance modules for the higher wattage then.

[J.P.M.]

Those are my thoughts as well, but wanted to get other input to make sure I'm not off base.

I put my answers inline below...



Thanks for the help!

You're welcome. Good luck.

[solarix]

I think you ought to at least have someone quote you on a SunnyBoy inverter.

[DaveDE2]

That's highly debatable. My 13kW system came out costing about $800 less in parts going with SMA vs Solaredge, including rapid shutdown. It's also highly debatable (and unlikely imo) that Solaredge would outproduce SMA in a shade-free environment. I'm getting 97.8% efficiency with the 6.0's right now. I'd be interested in knowing if Solaredge can come close to that.

[ButchDeal]

So you installed two inverters but could have installed one instead. Our costs would be cheaper with solarEdge even before labor. You then hit a great performance of 97.8%. SolarEdge is higher but you also would have more performance per module nearly all tier 1 modules come +x% -0%. It is that x% solarEdge can pull more from on no shadow roofs.

[DaveDE2]

No, I don't think so.

Solaredge 11.4kW inverter: $1970
36ea optimizers @ $65ea, $2340
total: $4371


SMA 5.0 $1541 x2 = $3082
SMA rapid shutdown $292
total: $3374

SMA savings $997

SolarEdge is NOT higher in efficiency. Even at (generous) max efficiency of 98% for the inverter and then 99% for the optimizers that puts them at 97.0 combined. The extra you mention for per panel efficiency will indeed draw in a little more power but at most is a wash imo.

Labor-wise, installing a rapid shutdown box is a snap compared to 36 optimizers.

[J.P.M.]

Overall, and only FWIW, and since you've done your homework, if it was me, I'd go w/D, #5 as being a fan of smaller is better than larger, or #6 if I wanted a bit more capacity - 12 % increase in capacity not being as much of an issue as the NPV of $3K extra (after tax credit) cost vs. the NPV of the extra power the larger array will provide.

Experience and working history with the vendor would tip the balance and my opinion toward that vendor.

[fordmantpw]

Actually, I'm leaning toward #6, for the reasons you mention.

[rmk9785e]

Which price/Watt is in this table of options - STC, PTC which is probably the same as CEC? What would be competitive $/W CEC in Northern California?

[ButchDeal]

comparison is generally done with STC, and pre incentive money

[fordmantpw]

You're gonna have to help me out with the acronyms. All listed costs are before incentives. I have no idea how that would compare with CA.

[J.P.M.]

You're gonna have to help me out with the acronyms. All listed costs are before incentives. I have no idea how that would compare with CA.

The common standard is STC == Standard Test Conditions = = output of a panel under test when the normal (perpendicular), and artificial by the way, irradiance (somewhat spectrally corrected to represent irradiance passing through 1.5 sea level air masses is equal to 1,000 W/m^2, while the temperature of the panel under test is maintained at 25 deg. C. That measured output is the number that appears on panel nameplates.

PTC, CEC and other test methods are similar, but mostly, IMO, useless and only serve to muddy the waters. They may be good to know but not worry too much about. See the book I referenced for the gory details. Sort of like knowing about ISO standards but living with the NEC or other national standards day/day when working in the U.S.

[rmk9785e]

comparison is generally done with STC, and pre incentive money

Sub $3/Watt is pretty good for the quotes being compared. The quotes I have received in California Central Valley are all between $3.19 to $4.16/W.

[J.P.M.]

Sub $3/Watt is pretty good for the quotes being compared. The quotes I have received in California Central Valley are all between $3.19 to $4.16/W.

Not to imply anything, but, the CA prices might be considered an example of selling to the market, or as it is sometimes thought, tacit price fixing, although there are probably too many players in the solar market for that to actually work.

[aliris]

I think the way the market is sold to in SoCal is that while $/W is quoted on pre-incentive prices, things are sold viscerally on that post-incentive price and the quoted price gets raised accordingly.

[fordmantpw]

Thanks for the help everyone. One thing I forgot to mention is that this is a shade-free environment. No trees or shade of any type near the roof.

[J.P.M.]

Thanks for the help everyone. One thing I forgot to mention is that this is a shade-free environment. No trees or shade of any type near the roof.

Good luck. I'd be interested to read how it all works out.

Regards,