Thoughts on this SolarCity proposal? **Photos inside**

[russ]

Is microinverter better? Because I asked the guy that is trying to sell me the kyocera system with central inverter told me it would cost $3,000 more to change to microinverter.

Always discussion about this but if you have a shade problem then microinverters or solar optimizers are necessary. No shade then string type is better.

The micros allow (for a price) one to see individual panel outputs - something to show the neighbor but pretty much useless otherwise.

[russ]

fit

You are either an engineer or someone who seems to know a lot about solar technologies.. so as I was almost ready to make up my mind then now I am not sure. I met up with this gentleman from the installation company that I thought would come out and tell me if the 24 panels canadian solar would fit on my roof, as it turned out, he was just another salesman. So now I hear there is another option- prepaid lease. He explained to me that it is like you are purchasing the system, but the company give you the cost after the 30% federal rebate and you own the system. So basically, if my system to purchase is $21K, I only have to pay $14,700 for a prepaid lease and that they would maintain the panels. So I asked them what do they do to maintain? couldn't really say much... This plan is different than PPA which I forget what it stands for but it is a lease. I think I need to get another quote. I feel a little uneasy with the purchasing from one company and then work with their contracted installer (so basically having to deal with 2 companies but save $4K). Another quote is needed I think.

Get several quotes - With any luck you will find a salesman that gives you confidence and you will learn more about pricing.

PPA - power purchase agreement

[skinnywalletana]

what parts?

Mod note within the text.

Is microinverter better? Because I asked the guy that is trying to sell me the kyocera system with central inverter told me it would cost $3,000 more to change to microinverter.

[skinnywalletana]

I thought the article seems to be tailored too...

Lots of thoughts on the article. As Russ said, it is tailored to promote a specific agenda. It is riddled with misleading or totally incorrect statements that cry out for refutation.

For a start:


Well, for a given cell type (say mono silicon) and number of cells, the Vmp voltage is remarkably constant with light level over the whole range which produces a significant amount of power. If you are trying to run your array by moonlight you will find that Vmp is reduced, but this is because of the internal leakage resistance inside the cells lowering the fraction of the output current that is available externally.
What does change is the available current, and the MPPT input needs to change its effective resistance to draw just the amount of current that will correspond to Vmp.
Some cheap MPPT devices cheat and instead of seeking the highest power point they just measure Voc and then assume that Vmp is around 80% of that. That strategy actually works surprisingly well in the absence of partial shade on the array.
The only times that the Vmp of a single panel will change significantly are:
1. The panel is at a much different temperature than the other panels. Both Vmp and Voc will be changed in the same ratio.
2. The panel itself is partially shaded. For a panel with three bypass diodes (three bypass cell groups) the Voc will remain pretty much unchanged but the Vmp will decrease to 2/3 or 1/3 of the full light value, depending on how bad the shade is. If the whole panel is equally shaded, the Vmp will be unchanged but Imp will be drastically cut.


This is basically total bull. If the bad panel is in one string of a group of parallel strings sharing a single MPPT input, then the output of that single string will suffer.
But if the bad panel is in a single string connected to an MPPT input and has working bypass diodes, all that will be lost will be the output of that single panel plus the energy wasted in the bypass diodes. (Note however that for a psuedo-MPPT device that estimates Vmp as a fraction of Voc the result will be bad for the whole string, since the current will be reduced to that produced by the bad panel. Some very low cost imported "MPPT" devices are believed to operate this way, FWIW. A true MPPT device will not have any problems with the situation.)

fit

You are either an engineer or someone who seems to know a lot about solar technologies.. so as I was almost ready to make up my mind then now I am not sure. I met up with this gentleman from the installation company that I thought would come out and tell me if the 24 panels canadian solar would fit on my roof, as it turned out, he was just another salesman. So now I hear there is another option- prepaid lease. He explained to me that it is like you are purchasing the system, but the company give you the cost after the 30% federal rebate and you own the system. So basically, if my system to purchase is $21K, I only have to pay $14,700 for a prepaid lease and that they would maintain the panels. So I asked them what do they do to maintain? couldn't really say much... This plan is different than PPA which I forget what it stands for but it is a lease. I think I need to get another quote. I feel a little uneasy with the purchasing from one company and then work with their contracted installer (so basically having to deal with 2 companies but save $4K). Another quote is needed I think.

[russ]

After reading this write up: http://energyinformative.org/are-sol...ral-inverters/Mod note - the site the link take you to is basically BS in a fairly nice package - wrong and misleading information in large quantities.

Sounds like micro inverters are better based on this article and also the mono crytalline panels are better. My husband doesn't like what is said about the potential life threatening issue with the central inverter
"Solar panels are connected in series before they are fed into a central inverter, typically with an effective nominal rating of 300-600 VDC (volts of direct current). This current is potentially life threatening.

Micro-inverters eliminate the need for high voltage DC wiring, which improve the safety for both solar installers and system owners."

So he basically say no to Sun Power or Kyocera since these two system comes with a central inverter and to get the micro inverter in place of the central, and extra $3,000 on top of already higher cost system.

I was almost ready to go with the Kyocera system if the company is willing to lower the price a bit. But now after reading this article, I should go with the least expensive system which is the monocrystalline with micro inverter. I am wondering if this article is biased? Any thoughts about the DC wiring?

Mod note within the text.

[inetdog]

I am wondering if this article is biased? Any thoughts about the DC wiring?

Lots of thoughts on the article. As Russ said, it is tailored to promote a specific agenda. It is riddled with misleading or totally incorrect statements that cry out for refutation.

For a start:

One of the tricky things about solar cells is that voltage needs to be adjusted to light level for maximum output of power. In other words, the performance of a solar panel is dependent on the voltage load that is applied from the inverter.

MPPT is a technique used to find the right voltage – the maximum power point. When MPPT is applied to each individual panel, as opposed to the solar system as a whole, performance will naturally increase.

Well, for a given cell type (say mono silicon) and number of cells, the Vmp voltage is remarkably constant with light level over the whole range which produces a significant amount of power. If you are trying to run your array by moonlight you will find that Vmp is reduced, but this is because of the internal leakage resistance inside the cells lowering the fraction of the output current that is available externally.
What does change is the available current, and the MPPT input needs to change its effective resistance to draw just the amount of current that will correspond to Vmp.
Some cheap MPPT devices cheat and instead of seeking the highest power point they just measure Voc and then assume that Vmp is around 80% of that. That strategy actually works surprisingly well in the absence of partial shade on the array.
The only times that the Vmp of a single panel will change significantly are:
1. The panel is at a much different temperature than the other panels. Both Vmp and Voc will be changed in the same ratio.
2. The panel itself is partially shaded. For a panel with three bypass diodes (three bypass cell groups) the Voc will remain pretty much unchanged but the Vmp will decrease to 2/3 or 1/3 of the full light value, depending on how bad the shade is. If the whole panel is equally shaded, the Vmp will be unchanged but Imp will be drastically cut.

If one solar panel in a string had abnormally high resistance due to a manufacturing defect, the performance of every solar panel connected to that same central inverter would suffer.

This is basically total bull. If the bad panel is in one string of a group of parallel strings sharing a single MPPT input, then the output of that single string will suffer.
But if the bad panel is in a single string connected to an MPPT input and has working bypass diodes, all that will be lost will be the output of that single panel plus the energy wasted in the bypass diodes. (Note however that for a psuedo-MPPT device that estimates Vmp as a fraction of Voc the result will be bad for the whole string, since the current will be reduced to that produced by the bad panel. Some very low cost imported "MPPT" devices are believed to operate this way, FWIW. A true MPPT device will not have any problems with the situation.)

[SunEagle]

So the $21K breakdown is this:

$13,160 for the system and the $7,632 is the cost for installation. I got this quote from Grape Solar which is affiliated with Costco (I told them when I got a quote from another company that actually came out went up the roof and told me 24 panels is how much can be installed, so I asked for a quote for 24 panels)

The installation company that works with Grape Solar is coming out this morning to make sure the 24 panels system does fit. Will keep you update.

Wow. $7632 for a 6360 watt system = $1.20/watt for installation. That is pretty good.

Please make sure that the costs include all of what is required including permitting and inspection approvals for a completely installed and working system. Hopefully it all works out for you.

[skinnywalletana]

That's what I am going to find out this morning...

It seems strange to see a 6360 watt system using microinverters costing less ($21k / 6360 watt = $3.3/watt) than a smaller 6000 watt system using a string inverter ($25k / 6000 watt = $4.17/watt).

Usually it is the other way around where a microinverter system costs more than a string inverter.

So the $21K breakdown is this:

$13,160 for the system and the $7,632 is the cost for installation. I got this quote from Grape Solar which is affiliated with Costco (I told them when I got a quote from another company that actually came out went up the roof and told me 24 panels is how much can be installed, so I asked for a quote for 24 panels)

The installation company that works with Grape Solar is coming out this morning to make sure the 24 panels system does fit. Will keep you update.

[SunEagle]

Micro inverters are about $150 per panel or so. 24 panels = $3600. How much is a string inverter?

It depends on the MFG. Also we are not only comparing the cost of specific components but the total installed cost which includes the labor and type of installation which can be higher than the material costs.

Just saying that most of what I have read on this forum showed a string inverter system costing less than a microinverter system. Of course you have to weigh in the type of panels and location of the installation.

So it is possible that skinnywalletana is getting a better deal with the canadian solar panels with micros with respect to the kyocera panels with a string inverter.

[J.P.M.]

Sure sounds like that it is. I was told if I want to switch to a micro inverter, I have to pay an extra $3,000 which would take the system to $28K

So looking at the system from a financial standpoint only, before federal rebate, I should go with the 24 canadian solar (6.36kw) which is monocrystalline and with the microinverter for $21K, about 4K less than the 24 kyocera solar (6.0kwh) which is polycrystalline with central inverter, which is $25K.

Appreciate all the posts and the posts responding to my questions. I have read and learned a lot about solar.

Before I spent 25 large on something, I'd like to learn about it too.

[JCP]

It seems strange to see a 6360 watt system using microinverters costing less ($21k / 6360 watt = $3.3/watt) than a smaller 6000 watt system using a string inverter ($25k / 6000 watt = $4.17/watt).

Usually it is the other way around where a microinverter system costs more than a string inverter.

Micro inverters are about $150 per panel or so. 24 panels = $3600. How much is a string inverter?

[SunEagle]

Sure sounds like that it is. I was told if I want to switch to a micro inverter, I have to pay an extra $3,000 which would take the system to $28K

So looking at the system from a financial standpoint only, before federal rebate, I should go with the 24 canadian solar (6.36kw) which is monocrystalline and with the microinverter for $21K, about 4K less than the 24 kyocera solar (6.0kwh) which is polycrystalline with central inverter, which is $25K.

Appreciate all the posts and the posts responding to my questions. I have read and learned a lot about solar.

It seems strange to see a 6360 watt system using microinverters costing less ($21k / 6360 watt = $3.3/watt) than a smaller 6000 watt system using a string inverter ($25k / 6000 watt = $4.17/watt).

Usually it is the other way around where a microinverter system costs more than a string inverter.

[skinnywalletana]

So it sounds like..

The article is a sales pitch for peddlers masquerading as experts. Follow the money. Folks on this forum may be rough around the edges sometimes, but they also, except for a couple of financial slug types, have no skin in the game, nothing to sell and collectively, while not always bullet proof on answers, usually do pretty good.

BTW, for the most part, central inverter systems usually cost less than micros.

Sure sounds like that it is. I was told if I want to switch to a micro inverter, I have to pay an extra $3,000 which would take the system to $28K

So looking at the system from a financial standpoint only, before federal rebate, I should go with the 24 canadian solar (6.36kw) which is monocrystalline and with the microinverter for $21K, about 4K less than the 24 kyocera solar (6.0kwh) which is polycrystalline with central inverter, which is $25K.

Appreciate all the posts and the posts responding to my questions. I have read and learned a lot about solar.

[J.P.M.]

I was in sales, a long time ago, and the one thing I learned (the hard way): people buy all kind of things for the wrong reason(s) all the time. That's just the way it is. And I'm no different. Human beings are not very rational. If we were, we'd all be driving crappy econo cars.

I spent about 10 yrs. as a sales rep. I did OK, but what I learned from real salespeople about human nature was invaluable and scary. As you, I'm also no different than most everyone else.

[JCP]

The article is a sales pitch for peddlers masquerading as experts. Follow the money. Folks on this forum may be rough around the edges sometimes, but they also, except for a couple of financial slug types, have no skin in the game, nothing to sell and collectively, while not always bullet proof on answers, usually do pretty good.

BTW, for the most part, central inverter systems usually cost less than micros.

I was in sales, a long time ago, and the one thing I learned (the hard way): people buy all kind of things for the wrong reason(s) all the time. That's just the way it is. And I'm no different. Human beings are not very rational. If we were, we'd all be driving crappy econo cars.