Looking for advice: is this a fair price?

[fraser]

Yep the higher tilt angle causes a loss of usable roof space. I think I also mentioned that as a reason the east west 10 degree racking is preferred, but there are a lack of options for that for residential flat roofs in seismic areas. The gain from 20 to 30 degree Tilt at the 37 parallel is negligible about 1.5% or so. It’s more about roof space optimization while maintaining the minimum row spacing. There is a calculator online if you need it. That’s what I used. However you might as well have the most northern row at the optimum tilt as shading isn’t a factor. One more row of 30 degree tilt since I need a 36 inch walkway for permitting. Also all tilted racking is in landscape as it fits my roof better. Racking cost differences are inconsequential compared to the roof utilization losses. Finally I’m pretty sure I mentioned that the bifacial cost is cheaper per watt, for just the front side. The back is just extra. The key for solar installation is optimizing your roof space and minimizing your.cost per installed watt. Not trying to get the most from every panel. Unless of course you have no roof space limitations. Everyone should be over sizing not right sizing like the sales people try to tell you.

[J.P.M.]

So there are two answers. 1) I have a flat roof . I wanted to go with 10 degrees east west tilt and regular panels but have been unable to find a residential provider. So panels will be tilted south’ish (196degrees) at 20 and 30 degrees. Tilting will be just enough to use the backside space which would have been wasted on inter row spacing without bifacial panels. 2) the panels are rated for the front side and they were the best price to size ratio that I found just for the front. It would be even more important with microinverters (fewer per watt) but they will clip a lot on 540w panels. Now I’ll just have to paint the roof white or something.

Interrow spacing in necessary to avoid array self-shading.
If the row pitch (the distance between the same point on any two rows) is too small, the more southerly panels will shade the more northerly panels.
That will more than kill any small advantage of bifacials which need a high(er) tilt, high albedo and a lot of open space behind them to add anything to array production.

If a sawtooth array is tightly packed (small row pitch), painting the roof white will gain little as a high proportion of the roof will be shaded and so will have nothing to reflect.

So as not to rehash a lot of the same material, see the thread you started on 05/13/22 that asked about row spacing calculators and such. My suggestions at that time were to get familiar with SAM. There may be other algorithms available that I'm unaware of that are openly available and there are some that are proprietary.
And, as I wrote in that other thread, also to know that, to a first approximation the highest annual output of any sawtooth array on a (mostly) horizontal roof is pretty much limited to the output of a flat, continuous array that's parallel to that roof.
Bottom line why: The higher tilt angle of a row (up to about the location latitude) will increase the annual output per square area of panel, but that is offset by the increased row pitch that is required because the increased panel tilts will require increased row pitch which will decrease the available panel area. It's one of those situations where there ain't no free lunch.

I worked on this for a couple of years back in the early ,80's and the early days of PC's. The horizontal array approximation, while not exact, is a semi fact of life in a practical sense and is not much affected by using bifacial panels which don't add much to most residential arrays. They might be worth a few cents more per PTC watt, but that's usually more than offset by the increased cost of racking and loss of area/output caused by the tilting requirements as described above.

Also, and in spite of what those who peddle bifacials would like us all to believe, bifacials for common residential horizontal roof applications (and most other residential applications s for that matter) are of little benefit.

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

[fraser]

Sorry forgot to answer planned layout. 6 rows of landscape 540 panels (4 or 3 to a row), middle and last rows at 30degrees (one for required 3 foot walkway) and rest at 20 degrees.

[fraser]

So there are two answers. 1) I have a flat roof . I wanted to go with 10 degrees east west tilt and regular panels but have been unable to find a residential provider. So panels will be tilted south’ish (196degrees) at 20 and 30 degrees. Tilting will be just enough to use the backside space which would have been wasted on inter row spacing without bifacial panels. 2) the panels are rated for the front side and they were the best price to size ratio that I found just for the front. It would be even more important with microinverters (fewer per watt) but they will clip a lot on 540w panels. Now I’ll just have to paint the roof white or something.

[J.P.M.]

I decided to change to a string inverter system with optimizers and using large bifacial panels, the total system cost is right about $1.2/w for a 10kw system.

A bit off topic, but what's your planned panel layout ? I ask because for most residential projects with panels parallel to a flat (but tilted) roof with about a 15 cm or less separation distance roof to panel, the output gain of a bifacial panel over a monofacial panel is pretty close to zero.
My apologies for mansplaining if you already know this or are designing a tilted, sawtooth array in reflective surroundings.

[SunEagle]

At .11 kWh and .13 for the service provider (National Grid), we have to assess the ROI. I worry far less about the kWh, it’s National Grid rates I’m most concerned about. They keep raising them, 45% in January.

Sounds like you have a good reason to install solar. I guess I am lucky my rates have gone up but only a fraction of a cent due to higher fuel costs. I am still paying about $0.10/kWh and it has been pretty stable for over 6 years.

[GDunk]

At .11 kWh and .13 for the service provider (National Grid), we have to assess the ROI. I worry far less about the kWh, it’s National Grid rates I’m most concerned about. They keep raising them, 45% in January.

[SunEagle]

Actually, I know that I will not install and I feel perfectly comfortable paying somebody to install our solar system. Looking at various quotes. I’ll have an idea of what is fair and whether I’m being scammed by some installers at least that’s my hope.

I hope all goes well for you. Keep us informed on how it goes.

[GDunk]

Actually, I know that I will not install and I feel perfectly comfortable paying somebody to install our solar system. Looking at various quotes. I’ll have an idea of what is fair and whether I’m being scammed by some installers at least that’s my hope.

[SunEagle]

I suppose you can spend whatever price they charge and say it’s reasonable, since essentially you are buying an asset and not paying for an expense. Buuuuut, I am actively pricing systems and when you get the installers to separate the labor/permits from the system cost, you see the big upcharge. The ones that don’t want to separate those costs, they are definitely overcharging. They know the costs for sure. I decided to change to a string inverter system with optimizers and using large bifacial panels, the total system cost is right about $1.2/w for a 10kw system. Labor and permitting should not be more than $1/w. Mine will be about .6-.7 based on the quote I received from my contractor, but I’ve shopped around a lot since I am using this as a test case. I’d like to get the cost of solar installation for everyone down to under $2/w. Really it should be about $1.5/w, before govt incentives. My quote above is buying through a U.S. intermediary, but buying panels and racking directly from the manufacturer would bring down the cost even more. I have found 2 manufacturers that offer sub .50/watt panels delivered to the US including customs. With transport costs coming down from the highs of the last 2 years, we should see better prices all around.

The problem is unless you have ever owned a business it is always hard to justify the cost. Remember the workers want more then minimum wage and that unfortunately drives up the cost to do business. Add to that the cost of owners equipment that you want to pay off also increases what the system may cost someone.

It sucks but unless you can perform a safe DIY you will end up paying someone more then you think it is worth.

[fraser]

I suppose you can spend whatever price they charge and say it’s reasonable, since essentially you are buying an asset and not paying for an expense. Buuuuut, I am actively pricing systems and when you get the installers to separate the labor/permits from the system cost, you see the big upcharge. The ones that don’t want to separate those costs, they are definitely overcharging. They know the costs for sure. I decided to change to a string inverter system with optimizers and using large bifacial panels, the total system cost is right about $1.2/w for a 10kw system. Labor and permitting should not be more than $1/w. Mine will be about .6-.7 based on the quote I received from my contractor, but I’ve shopped around a lot since I am using this as a test case. I’d like to get the cost of solar installation for everyone down to under $2/w. Really it should be about $1.5/w, before govt incentives. My quote above is buying through a U.S. intermediary, but buying panels and racking directly from the manufacturer would bring down the cost even more. I have found 2 manufacturers that offer sub .50/watt panels delivered to the US including customs. With transport costs coming down from the highs of the last 2 years, we should see better prices all around.

[GDunk]

In my region $3.50 watt seems to be common.

[SunEagle]

Isn’t $/watt dependent on location? Won’t New England be a higher cost per watt than southern states?

I feel it comes down to what the installers are charging. Here in Florida I have seen costs above $3 per watt but since my cost of electricity is way below New England it makes it harder to justify any system installed by others.

[GDunk]

Isn’t $/watt dependent on location? Won’t New England be a higher cost per watt than southern states?

[fraser]

If you are paying more than $3/w, installed, then you are paying too much. solar reviews and solar estimate.org, and similar online quoting services will get you under $3/w. If you want to buy the equipment and just pay for labor and the permitting, you should be closer to $2/w.