CSI EPBB Calculator Question

[Volusiano]

Thanks Vol, that's really interesting and surprising. Especially since as you said new inverters aren't needed. Did they explain their rationale? Do you have a pretty high level of trust and confidence in them?

I don't remember which panels you have but many have prices online.

I have the Canadian Solar CS6P-250P panels. I've seen prices around $200-$250 for them. At this range, the panel cost would be around 35-44% of the expansion quote.

They didn't explain their rationale. They just gave me a quote like I asked for and that was it. I have not bought the new EV yet, so I'm not ready to engage with them on the expansion seriously yet anyway. So I didn't want to go too deep into a conversation that I'm not ready to have yet.

But I was very happy with their installation and I would say they're trustworthy. They originally proposed 1 big inverter (an 8K Sunny Boy for simplicity) but I told them I preferred a 7K and a 4K instead. 1 inverter would still work OK according to the Sunny Design website but would slightly reduce the energy usability factor to 99.6%. They said no problem, they could do it for the same price. As it turns out, the 7K and 4KTL can handle 12 more panels if I wanted to without having to add more inverter. If I went with the 8K like they wanted, it wouldn't be able to handle any more than the 44 already in place. So that's why I was a little bummed that the expansion quote wasn't more than 8% lower in price without a new inverter.

[J.P.M.]

About over sizing -- it occurs to me that likely the cost of a system could broken down in many ways, here is one hypothetical.

1. Fixed "set up" or "start up" -- design, shipping, transportation of materials, minimum cot to get job going, etc
2. Materials, mostly panels
3. Labor

What I'm getting at is that incremental increase in kW of system will be incrementally lower cost than that kW proportion of system itself. Hypothetically anyway (disclaimer).

This might lead to "do it all now" thinking in scenarios with greater future uncertainty. Eg. Changing rates, changing electricity use (family size, lifestyle, electric vehicles, etc.)

On the other side of the unknown is advances in technology. Look at the differences in phones from just ten years ago.

While I'm on the subject is there a rule of thumb for improvement in solar cell improvements analogous to Moore's Law, which has been accurate since 1970 in stating that processing power will double approximately every two years?

One smart guy here has back calculated the increase in power rates for San Diego over the last ten p,us tears, has anyone computed that for solar panel electricity production?

More like fixed and variable costs. Material costs - panels, racking, wiring, inverters to some degree, more so for micros I'd bet, are more variable and job size related. The cost of running an office, having a truck, inventory, permitting, insurance, etc. probably tends to be more fixed. For example, it'll cost about as much to a vendor for insurance on the truck that shows up at your house with 16 panels as 24, that's a fixed cost. I think Naptown had some comment on this sort of thing not too long ago. Bigger systems tend to cost less to assemble, hence probably less cost to the customer per Watt, the fixed costs being spread over more panels, hence a lower cost per Watt.

"do it all now" can also be do it less now - or not at all now, maybe later - kids will be gone, efficiency improvements will lower my demand, I'm moving in 10 yrs. etc. Believe it or not, (and FWIW, I'm not sure I do, but I'm just sayin'), one of the implied, if not stated goals of AB 327 is to adjust rates in the upper tiers downward from the draconian levels they're at now. If that does occur, high usage customers could possibly see a decrease in their bills. That would make oversized systems less cost effective than they are already. (And, BTW, perhaps make the monthly fixed payment of a lease plus remaining new (reduced) bill greater than the new cost of electricity by itself with no solar electric).

I think I may be the person who back calculated SDG & E rate increase for the last 10 yrs., 11 now. I did it because I wanted to try to make sense of the B.S. vendors were, and still are spewing about utility rate increases. For those who may have missed it, that per yr. ave. compounded rate increase is a relatively strong function of monthly usage, varying between about 1.8 %/yr. for about 6,000 kWhrs./yr. to about 5-6%/yr. for about 15-16,000 kwhrs./yr. usage - at least for SDG & E- and quite "choppy", with several years showing an actual decrease. It's a somewhat weak function of seasonal variation.

Solar electricity production has been increasing but is still a rather small fraction of the total. Reliable #'s are somewhat hard to come by.

[silversaver]

I have the Canadian Solar CS6P-250P panels. I've seen prices around $200-$250 for them. At this range, the panel cost would be around 35-44% of the expansion quote.

They didn't explain their rationale. They just gave me a quote like I asked for and that was it. I have not bought the new EV yet, so I'm not ready to engage with them on the expansion seriously yet anyway. So I didn't want to go too deep into a conversation that I'm not ready to have yet.

But I was very happy with their installation and I would say they're trustworthy. They originally proposed 1 big inverter (an 8K Sunny Boy for simplicity) but I told them I preferred a 7K and a 4K instead. 1 inverter would still work OK according to the Sunny Design website but would slightly reduce the energy usability factor to 99.6%. They said no problem, they could do it for the same price. As it turns out, the 7K and 4KTL can handle 12 more panels if I wanted to without having to add more inverter. If I went with the 8K like they wanted, it wouldn't be able to handle any more than the 44 already in place. So that's why I was a little bummed that the expansion quote wasn't more than 8% lower in price without a new inverter.

I guess the installer still need to submit another permit request...etc. I think it might cost them another $1500 to $2000 just like you apply for a new solar system. This is why I want to get the system all setup that is ready for feature (young growing family + EV). Begin with a larger system, cost is going to be much lower than add on later. Lucky you don't need a new inverter If I need to expand my solar array, I think my cost will be much higher than yours. I'm sure I need a new inverter.

[Volusiano]

I guess the installer still need to submit another permit request...etc. I think it might cost them another $1500 to $2000 just like you apply for a new solar system. This is why I want to get the system all setup that is ready for feature (young growing family + EV). Begin with a larger system, cost is going to be much lower than add on later. Lucky you don't need a new inverter If I need to expand my solar array, I think my cost will be much higher than yours. I'm sure I need a new inverter.

Really? You think the permit stuff would cost that much $1500-$2000? Wow, I would guess it may come out to a few hundred bucks, $500 top. But what do I know? I never applied myself.

[J.P.M.]

I have the Canadian Solar CS6P-250P panels. I've seen prices around $200-$250 for them. At this range, the panel cost would be around 35-44% of the expansion quote.

They didn't explain their rationale. They just gave me a quote like I asked for and that was it. I have not bought the new EV yet, so I'm not ready to engage with them on the expansion seriously yet anyway. So I didn't want to go too deep into a conversation that I'm not ready to have yet.

But I was very happy with their installation and I would say they're trustworthy. They originally proposed 1 big inverter (an 8K Sunny Boy for simplicity) but I told them I preferred a 7K and a 4K instead. 1 inverter would still work OK according to the Sunny Design website but would slightly reduce the energy usability factor to 99.6%. They said no problem, they could do it for the same price. As it turns out, the 7K and 4KTL can handle 12 more panels if I wanted to without having to add more inverter. If I went with the 8K like they wanted, it wouldn't be able to handle any more than the 44 already in place. So that's why I was a little bummed that the expansion quote wasn't more than 8% lower in price without a new inverter.

V: I'm not taking sides here, but perhaps the vendor doesn't get as high a markup, or O.E.M./vendor discount on what may be an expensive component (inverters) as they might on wiring/racking/etc., and so can't pass through savings that may not be there to the same extent as for other materials. Or, they may get a real high discount, making the inverter cost a rather small portion of the total job cost, meaning saving to pass through also aren't there to begin with. Either way, perhaps there is not much of a spread between what the vendor pays for the inverter and what the vendor charges for the inverter as there is for some other components -->> less to pass through. I also wonder if there is not as much labor associated with an inverter as with for example, racking, hence, less in the way of labor cost savings to pass along. The truck still has to show up and I'd guess most of the labor is maybe close to what 12 more panels without an inverter would be compared to 12 panels with an inverter, and not a whole lot of material to spread the fixed costs around to. Still, 8% seems a bit low to me also, but I'm not in any position to have an intelligent opinion on it.

FWIW

[silversaver]

Really? You think the permit stuff would cost that much $1500-$2000? Wow, I would guess it may come out to a few hundred bucks, $500 top. But what do I know? I never applied myself.

Not just permit, the installer has re apply to your utilities company and just like apply a new solar system.

I think Naptown might have better answer for you. As I recall when my friend add solar array to his exist solar system, the cost is higher per Watt since the system is smaller.

[J.P.M.]

Like I said, doesn't matter V1, V2 or CSI calculator, they came pretty close in CA 92887. If you base on your zip code, you probably getting 600 to 700 more with PVWatt. I have never said vendor or I using CSI calculator as sizing tool, it just happen those datas were used as expected generation in Locus monitoring.

I'll say this one more time and then shut up about it: I'm of the opinion that the .77 default factor that PV Watts uses is most often unrealistically low and most people are unaware of it, resulting in systems being less cost effective because they are oversized, usually by 10% or more. Whether oversizing is the customer's intent or not is not my concern or business, but I believe it's better to start with more accurate information about expected performance. My experience is that better, more cost effective equipment that is more fit for purpose is more likely to be one result.

[silversaver]

I'll say this one more time and then shut up about it: I'm of the opinion that the .77 default factor that PV Watts uses is most often unrealistically low and most people are unaware of it, resulting in systems being less cost effective because they are oversized, usually by 10% or more. Whether oversizing is the customer's intent or not is not my concern or business, but I believe it's better to start with more accurate information about expected performance. My experience is that better, more cost effective equipment that is more fit for purpose is more likely to be one result.

I know what you mean, but can you listen to what I'm telling you? You have all my datas, please plug them in both CSI calculator and PV Watt V1 or V2. The result from CSI is 9,972kWh vs. PV Watt 10,215kWh using (SolarAnyWhere weather. If I use TM3, the result is lower a 9600s. )

I know your point trying to say vendors usually offering oversize system to gain profit. In my case, the few hundreds kWh per year doesn't really matter. The weather has more affect than that per year.

[albert436]

Comments in bold within the text

Thanks russ, yeah I get you.

If you think however that I was suggesting that Moore's Law would apply to solar panels, well then, OK never mind.

[Naptown]

OK here is my take on why it costs more to do an add on in most instances but not all.
Depending on the AHJ they may require structural engineering on the addition of only one panel.
It costs more per panel to ship a small amount than to ship a pallet or more. Ones and two's cost a fortune.
Building permit costs the same or more per panel depending on the permit cost structure of the AHJ.
If the system is an enphase and there are < 17 panels or more than 17 panels existing then there is infrastructure there existing to add up to 17 modules per string of modules. I it does not fall into this there there is a need for more wiring to be done.
If the service is large enough to accommodate the additional panels without having to change to a line side tap then all is good.

Here is an idea of what it would cost in Washington DC to permit an addition.

Plat from City $85.00
Someone to draw up the site plan and one line drawing $100.00
Structural engineering (wet stamped plans) and structural drawings.$1200-1500
Basic permit fee $35.00
Labor to run permit $100 This can tie up one person all day but this is an average.
Gas mileage and parking to get permit $50.00 (it may be less but this is what it costs us at the IRS rate and we are 25 miles away from permit office)
Actual permit fee $35.00 + 2% of module cost which they determine to be $1500 each so it may vary
Time to register the SREC's and do the interconnect agreement say $50 each or $100
So adding that up it costs to add 2 panels a total of about $1700.00
This is the non marked up cost to the contractor on top of labor and materials.
I would expect a contractor to mark these items up as they are costs like anything else and there is overhead and a profit to be made.

[Naptown]

I'll say this one more time and then shut up about it: I'm of the opinion that the .77 default factor that PV Watts uses is most often unrealistically low and most people are unaware of it, resulting in systems being less cost effective because they are oversized, usually by 10% or more. Whether oversizing is the customer's intent or not is not my concern or business, but I believe it's better to start with more accurate information about expected performance. My experience is that better, more cost effective equipment that is more fit for purpose is more likely to be one result.

I agree with your assessment of PV watts and you are correct the system should be derated according to the specifications of the components and wiring and not by a default derate.

[J.P.M.]

I know what you mean, but can you listen to what I'm telling you? You have all my datas, please plug them in both CSI calculator and PV Watt V1 or V2. The result from CSI is 9,972kWh vs. PV Watt 10,215kWh using (SolarAnyWhere weather. If I use TM3, the result is lower a 9600s. )

I know your point trying to say vendors usually offering oversize system to gain profit. In my case, the few hundreds kWh per year doesn't really matter. The weather has more affect than that per year.

At the risk of breaking my word, I was looking at your Jan. stuff while composing a different rant 1-2 days ago to Bando and noticed how much your Jan. data overshot the est. like hers did, for what I believe is a month that I measured, in spite of what my gut, perception and sensibilities all tell me, as being not that much sunnier than normal. Can you post or P.M. the monthly data you have so far ? I'll ask the same of Bando if she ever talks to me again.

[Volusiano]

OK here is my take on why it costs more to do an add on in most instances but not all.
Depending on the AHJ they may require structural engineering on the addition of only one panel.
It costs more per panel to ship a small amount than to ship a pallet or more. Ones and two's cost a fortune.
Building permit costs the same or more per panel depending on the permit cost structure of the AHJ.
If the system is an enphase and there are < 17 panels or more than 17 panels existing then there is infrastructure there existing to add up to 17 modules per string of modules. I it does not fall into this there there is a need for more wiring to be done.
If the service is large enough to accommodate the additional panels without having to change to a line side tap then all is good.

Here is an idea of what it would cost in Washington DC to permit an addition.

Plat from City $85.00
Someone to draw up the site plan and one line drawing $100.00
Structural engineering (wet stamped plans) and structural drawings.$1200-1500
Basic permit fee $35.00
Labor to run permit $100 This can tie up one person all day but this is an average.
Gas mileage and parking to get permit $50.00 (it may be less but this is what it costs us at the IRS rate and we are 25 miles away from permit office)
Actual permit fee $35.00 + 2% of module cost which they determine to be $1500 each so it may vary
Time to register the SREC's and do the interconnect agreement say $50 each or $100
So adding that up it costs to add 2 panels a total of about $1700.00
This is the non marked up cost to the contractor on top of labor and materials.
I would expect a contractor to mark these items up as they are costs like anything else and there is overhead and a profit to be made.

Thanks for the detailed cost layout, Naptown. It looks like the biggest part of the cost would be a structural engineering and drawing plan for $1200-$1500. I'm not sure if my installer ever did one. All I saw was a layout of where the panels go on the roof and where the inverters and boxes will be placed on the house. I also saw an electrical schematic drawn up for the system. But there was no paperwork seen for a structural drawing plan and nobody mentioned to me about having a structural study done on my house. So how do I know whether they spent the money on doing a structural study on my house or not?

Also, if this is an expansion of an already existing design, can't they reuse the original structural study (if they ever did one)? It doesn't make sense that this would have to be done twice. The structure of the house hasn't changed from before afterall, except for the original panels on the roof that were already approved anyway.

[Naptown]

Thanks for the detailed cost layout, Naptown. It looks like the biggest part of the cost would be a structural engineering and drawing plan for $1200-$1500. I'm not sure if my installer ever did one. All I saw was a layout of where the panels go on the roof and where the inverters and boxes will be placed on the house. I also saw an electrical schematic drawn up for the system. But there was no paperwork seen for a structural drawing plan and nobody mentioned to me about having a structural study done on my house. So how do I know whether they spent the money on doing a structural study on my house or not?

Also, if this is an expansion of an already existing design, can't they reuse the original structural study (if they ever did one)? It doesn't make sense that this would have to be done twice. The structure of the house hasn't changed from before afterall, except for the original panels on the roof that were already approved anyway.

Good point about the structural part. It may or may not be needed. However it is my experience with engineers that they will look at the addition as closely as the original and charge the same for the wet stamped drawings. Keep in mind that their license is on the line therefore the same due diligence is required. And this requirement is becoming universal among jurisdictions

[silversaver]

At the risk of breaking my word, I was looking at your Jan. stuff while composing a different rant 1-2 days ago to Bando and noticed how much your Jan. data overshot the est. like hers did, for what I believe is a month that I measured, in spite of what my gut, perception and sensibilities all tell me, as being not that much sunnier than normal. Can you post or P.M. the monthly data you have so far ? I'll ask the same of Bando if she ever talks to me again.

Ok, this is the last time I'll talk about this. Estimate is just an estimate. Please feel free to take a look of each screenshoot, and I hope you have a better idea what I'm say. They aren't really much different. Our vendor (bando and I) hasn't over sizing our systems. I know you don't like them, but please let it go....