Advice needed on Proposals - 9.6 KW - upstate NY

[gcherian]

Hello everyone, I have been reading this forum for about a week now and I have gotten my first proposal. So I thought I would put it here for another set of eyes and ideas. First about my situation - Located in upstate NY (lots of snow), house direction and trees not ideal for roof mount but lots of open pasture available for ground mount. I use about 11,685 units per year. I have read the dummies book, did a lot of reading online about anything I could get my hands on - went to a SolarizeCNY workshop and decided to get 4 to 5 offer before making a decision. Got offer #1 and #2, #3 coming this Wednesday and another couple in progress.

System as designed by #1
9.6 KW
30 JA Solar 320w panels
SE7600 Inverter with optimizers
Ground mount (about 75 feet of trenching)
Cost - $3.23/w (before all rebates and incentives)

System as designed by #2
11.56 KW
34 Q-Cell 340w panels
SE10000 Inverter with optimizer
consumption meter included
Ground mount (about 100 feet of trenching)
Cost - $2.92/w (before all rebates and incentives)

1. I am surprised for the same amount of units used per year (11,685) that 2 installers came with 2 system capacity. I think #2 is over conservative and #1 is a little optimistic. But #1 is willing to offer 5 year performance guarantee and 20 year warranty with their finance offer.

2. Any thoughts or comments on the above?

Any other insights on this would be greatly appreciated. Again apologize for yesterday - I could not cut and paste what I types into this form.

Thanks again.

[J.P.M.]

Well, that was informative.

[gcherian]

I know right - for what ever reason I am not able to cut and paste what I wrote from the notepad to the editor here - gets cut off at Hello everyone. I am going to try again. Sorry.

[ButchDeal]

System as designed by #1
9.6 KW
30 JA Solar 320w panels
SE7600 Inverter with optimizers
Ground mount (about 75 feet of trenching)
Cost - $3.23/w (before all rebates and incentives)

System as designed by #2
11.56 KW
34 Q-Cell 340w panels
SE10000 Inverter with optimizer
consumption meter included
Ground mount (about 100 feet of trenching)
Cost - $2.92/w (before all rebates and incentives)

1. I am surprised for the same amount of units used per year (11,685) that 2 installers came with 2 system capacity. I think #2 is over conservative and #1 is a little optimistic. But #1 is willing to offer 5 year performance guarantee and 20 year warranty with their finance offer.

2. Any thoughts or comments on the above?

.

#1 9.6kw is a bit much for an SE7600. I would put this on an SE10000 there is not that much difference in cost

#2 more reasonable over size


as for the two different capacities. what were their production estimates for these two systems?

[J.P.M.]

I'd do my own output estimate w/ PVWatts and then see if I could figure out why the difference in sizing.

BTW, what's your zip ?

[gcherian]

#1 9.6kw is a bit much for an SE7600. I would put this on an SE10000 there is not that much difference in cost

#2 more reasonable over size


as for the two different capacities. what were their production estimates for these two systems?

The first estimate FY production was estimated at 11984 (or 101% of usage) and second one at 12224.

[gcherian]

I'd do my own output estimate w/ PVWatts and then see if I could figure out why the difference in sizing.

BTW, what's your zip ?

Based on PVWatts Quote #1 is in range - it says about 12010 kwh per year (for 9.6 KW, standard panel, 35 degree at 180 south). Zip is 13032
I do not understand how Quote #2 estimated the system so high.

Thank you.

[ButchDeal]

Based on PVWatts Quote #1 is in range - it says about 12010 kwh per year (for 9.6 KW, standard panel, 35 degree at 180 south). Zip is 13032
I do not understand how Quote #2 estimated the system so high.

Thank you.

is there shadowing?

[gcherian]

is there shadowing?

Nope - open field. Attached is the image created by installer #2 - pretty much the array can go anywhere in the open field.
array_location.png

[J.P.M.]

Based on PVWatts Quote #1 is in range - it says about 12010 kwh per year (for 9.6 KW, standard panel, 35 degree at 180 south). Zip is 13032
I do not understand how Quote #2 estimated the system so high.

Thank you.

As Butch notes, could be shadowing/shade. Might also/or/+ be different parameters used in estimating models used. Many folks find a 10 % loss parameter seems to give better agreement w/actual output when using PVWatts, which, as you probably know, also takes no account of shading.

BTW, old home week: I dated someone from VVS H.S. between Jr.- Sr.yr. high school that I met at Sylvan beach, but that was in the 60's. I also had some shirttail relatives in Chittenango - long gone now.

[sensij]

Based on PVWatts Quote #1 is in range - it says about 12010 kwh per year (for 9.6 KW, standard panel, 35 degree at 180 south). Zip is 13032
I do not understand how Quote #2 estimated the system so high.

Thank you.

PVWatts doesn't really do anything to estimate loss from snow cover. Could installer 2 be assuming they will be buried for some portion of the winter?

[gcherian]

BTW, old home week: I dated someone from VVS H.S. between Jr.- Sr.yr. high school that I met at Sylvan beach, but that was in the 60's. I also had some shirttail relatives in Chittenango - long gone now.

Small world...lol


---- Could be either of the issues that has been raised. Either way which is the ideal option for me - I do not want to be spending money over-building if it is not needed for the situation/application. We still have couple more quotes coming - that should give a general idea for sure.

Thank you.

[gcherian]

So - now I have 3 additional quotes

The price / installed watt - range from $2.90 to $ $3.45 (before all rebates and incentives + all ground mount)
All are using SolarEdge inverters
The system size range from 11.56 KW to 9.6 KW for annual usage of 11685 watts.

The biggest system (11.56 KW comes with the lowest per watt cost $2.90)
The cheapest out of pocket system (10.2 KW @ 3.17) only offers 5 year warranty

Panels are

QCell 300W, JA Solar 320W and Trina 275W

At this time, I am thinking these are all very close to everything and I should go with who I am most comfortable working with. Or am I missing anything or overlooking anything?

How to make the final decision?

Thank you for all your help and insights...

[J.P.M.]

So - now I have 3 additional quotes

The price / installed watt - range from $2.90 to $ $3.45 (before all rebates and incentives + all ground mount)
All are using SolarEdge inverters
The system size range from 11.56 KW to 9.6 KW for annual usage of 11685 watts.

The biggest system (11.56 KW comes with the lowest per watt cost $2.90)
The cheapest out of pocket system (10.2 KW @ 3.17) only offers 5 year warranty

Panels are

QCell 300W, JA Solar 320W and Trina 275W

At this time, I am thinking these are all very close to everything and I should go with who I am most comfortable working with. Or am I missing anything or overlooking anything?

How to make the final decision?

Thank you for all your help and insights...

Since you ask:

It comes down to most bang for the long term buck for what you want to accomplish. Most long term cost effectiveness and low initial cost are not the same.

Getting the most long term cost effectiveness often involves balancing priorities and some tradeoffs.

Assuming you have chosen to get a PV system over other means of offsetting your electric bill, one high project priority is vendor quality. Whatever size system you choose, the vendor must know what they are doing, and also be ethical, before you can have any trust in them. Good equipment can be short circuited by poor quality installation. Choose a vendor wisely, deliberately and carefully. Read this paragraph again.

Also, Download and read:" Solar Power Your Home for Dummies". A free net download for a slightly dated version, or ~ $25 for a newer hardcopy at bookstores/Amazon. Knowledge is power. Read the book and get some of both. Comes in very handy during negotiations. You'll find out some of how much vendors don't (or do) know. A valuable education in itself.

The size disparity in your quotes would be a concern to me. In the best of all worlds, and before you called any vendors, you would have a good idea of :

1.) What your current usage is and not only what, but how you are charged for it. You seem to have current usage.
2.) At least a SWAG of what your plans are and how those plans affect your future electrical use.
3.) An estimate of what ground mount PV systems in your area cost. The vendors know. Ask them via quotes and they'll tell you higher. Find out on your own or get as much info as possible.
4.) How much a system with your constraints will produce per installed kW in a "typical" year. As you have already done, you can use the PVWatts estimates for some/most of that (and read the help/info screens for info on limitations and assumptions the model uses), but, as we know, you'll need to adjust that estimate for shading somehow. There are shading tools available. Some vendors use them. Snoop around in the quotes and see if any of them include a shade analysis, and if so, to what degree, if any they seem to agree. I've found I can get an educated SWAG on shade without tools but I'm a bit eccentric about such things and have been at it a while.
5.) How much of your current and estimated future usage you want to offset. With a short study of the time value of money, you may well come to the conclusion that a 100 % offset is not the most cost effective choice in system size.
6.) Whatever your priorities, divide your chosen annual system production (your goal) as determined/estimated from above, and divide that by your educated estimate of the per kW output of a system as you envision it. The result will be an estimate of the system size (in kW) that will probably get close to meeting your goals as far as bill offset goes, +/- about 10 % per year. This is not an exact science.

As you've already done most of the above, and that's a lot, you could do a lot worse. Read the book. Go over the quotes. Choose your size, and CAREFULLY choose a vendor thinking long term and most bang for the buck based on how and what you want for system performance. Use you knowledge and negotiating skills ( and remember - EVERYTHING is negotiable) to get the best quality for the best price. Be deliberate. You have time. This is not a race.

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

Good Luck.

[gcherian]

Thank you very much for the reply - everything you say does make sense. I do have the free book as PDF and did skim through it - maybe I will go through it again over the weekend.

Thank you.