Solar Panels

[mwalsh]

Hey OCC! I agree with Boomer....pretty darn good for a system of that size!

Boomer....would love to share production numbers with you. You PM me yours and I'll PM you mine!

 

[Boomer23]

Hey OCC! I agree with Boomer....pretty darn good for a system of that size!

Boomer....would love to share production numbers with you. You PM me yours and I'll PM you mine!

Fine with me Michael, but we're headed into a week of mostly rainy days, so a) production will be quite disappointing for a week or so and b) even though we're only about 10 miles apart, cloud conditions will vary during storms, so comparisons will be dicey. That said, PM away!

 

[occ]

Hey guys, I just found this thread.

I got a 4kw system (but only half of the panels is facing south, the other half is facing north - not enough room on the south roof - so my system is not 100% "optimized"). Today I generated 10.38kwh.

Check out my output:

http://solarweb.fronius.com
username: public
password: public

Then click "PV Systems" tab, then "Tustin0 (QT)".

My archive data is not complete due to software/website/computer issues for the last 3 yrs.

Hi occ. Actually, that's pretty darn good output for a system with half the panels facing north. Based on my system's output of 13 kWh today, that's right on target for the relative sizes of our systems, but all of my panels are facing south, or actually SSW.

Are you sure that they are north facing and not west? I know, stupid question. You know your own roof layout.

Dang it...brain fart... You're pretty sharp Boomer. My system is South and "WEST" facing not "North" as I stated. I would not have that kind of production if it were North.

 

[Gonewild]

boomer is your system 215 x24 panels that is my Sunpower set I would like to see your numbers

 

[mwalsh]

Shall we make another thread? We can each start a post that outlines our system and then edit it daily to add the production numbers?

 

[Gonewild]

That would be cool short term after the sun comes back I would be most interested in summer sun as my angle is 20 deg's which give me more in summer when the cost of power is the most.

 

[JPVLeaf]

I just noticed this thread and would also like to compare our PV production, since we are all
in the same general area (central/south OC).

MWalsh and Garygid. Could you share what direction your panels are facing?
From what I recall, Boomer (SSW) and OCC (1/2 S, and 1/2 W).

All our panels are west-facing (magn. 257°, true 270°), and we have a std. pitch of 19°.
Yesterday, our production was 8.1 kwh (4.3 kw dc).

Our system has been up an running for approx. 2 mos. and I sometimes feel like ours may be
underperforming given original production projections and hearing your all's production nos.

 

[mwalsh]

MWalsh and Garygid. Could you share what direction your panels are facing?
From what I recall, Boomer (SSW) and OCC (1/2 S, and 1/2 W).

I just started that new thread, entitled "Our Solar Production" - feel free to add a post!

 

[JPVLeaf]

I just started that new thread, entitled "Our Solar Production" - feel free to add a post!

Oh, okay. I just missed it. Thanks.

 

[mwalsh]

Here's the link:

http://www.mynissanleaf.com/viewtopic.php?f=13&t=2029

 

[turbo2ltr]

So my house is oriented rather poorly.

My gut tells me that putting half the panels on one side of the ridge line and half on the other would give a better "under the curve" coverage. Or am I completely off on this?

How much of a difference would racking the panels so they were facing up and south (instead of flat against the roof) make?

 

[DaveEV]

How much of a difference would racking the panels so they were facing up and south (instead of flat against the roof) make?

Yep - you'd lose a lot in aesthetics, but racking tilting them up so they face nearly south would help a LOT.

Of course, if you can afford to simply make up the difference by adding more panels then you don't have to worry about it.

You can run the numbers at PVwatts to see what kind of difference it makes - figure about 15-20% decrease in output for facing west or east instead of south.

For example, here's a direct link to the PVwatts estimator for Phoenix: http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/US/Arizona/Phoenix.html

Using a sample 4kW system:

Tilted 20* south (180*) you get about 6400 kWh/year.
Tilted 20* east (90*) you get about 5500 kWh/year.
Tilted 20* west (270*) you get about 5400 kWh/year.

Looks like you tend to get afternoon clouds in Phoenix - hence the lower output for an array facing west vs east.

So to make the same amount of power as an "ideal" system, you'd need about 4.65 kW instead of a 4kW system to make the same power.

My gut tells me that putting half the panels on one side of the ridge line and half on the other would give a better "under the curve" coverage. Or am I completely off on this?

Only if you have shading issues that would affect enough panels that would offset any east/west production discrepancy. One thing to keep in mind is that if you have panels facing in significantly different directions, you should use separate inverters for each set of panels facing a single direction (or use microinverters).

For your house in Phoenix, you'd want to put most of your panels on the east facing roof because it is facing slightly south and it appears that you get to get afternoon clouds. I imagine that heat tends to be worse in the afternoons, too which would affect afternoon output more.

If you can get them on racks that angle them more to the south then that's good, but often it's cheaper to add more panels than to add more complicated tilt racking hardware.

 

[Boomer23]

boomer is your system 215 x24 panels that is my Sunpower set I would like to see your numbers

I'll post some example outputs here in a few days, Gonewild. But comparing coastal Southern California with Arizona is not going to be highly instructive. That said, my peak output on the longest, sunniest summer days is 33 kWh. My total annual output is about 8600 kWh.

 

[LEAFfan]

How much of a difference would racking the panels so they were facing up and south (instead of flat against the roof) make?

Yep - you'd lose a lot in aesthetics, but racking tilting them up so they face nearly south would help a LOT.

Of course, if you can afford to simply make up the difference by adding more panels then you don't have to worry about it.

You can run the numbers at PVwatts to see what kind of difference it makes - figure about 15-20% decrease in output for facing west or east instead of south.

For example, here's a direct link to the PVwatts estimator for Phoenix: http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/US/Arizona/Phoenix.html

Using a sample 4kW system:

Tilted 20* south (180*) you get about 6400 kWh/year.
Tilted 20* east (90*) you get about 5500 kWh/year.
Tilted 20* west (270*) you get about 5400 kWh/year.

Looks like you tend to get afternoon clouds in Phoenix - hence the lower output for an array facing west vs east.

So to make the same amount of power as an "ideal" system, you'd need about 4.65 kW instead of a 4kW system to make the same power.

My gut tells me that putting half the panels on one side of the ridge line and half on the other would give a better "under the curve" coverage. Or am I completely off on this?

Only if you have shading issues that would affect enough panels that would offset any east/west production discrepancy. One thing to keep in mind is that if you have panels facing in significantly different directions, you should use separate inverters for each set of panels facing a single direction (or use microinverters).

For your house in Phoenix, you'd want to put most of your panels on the east facing roof because it is facing slightly south and it appears that you get to get afternoon clouds. I imagine that heat tends to be worse in the afternoons, too which would affect afternoon output more.

If you can get them on racks that angle them more to the south then that's good, but often it's cheaper to add more panels than to add more complicated tilt racking hardware.

Afternoon clouds? Have you ever lived here drees? We RARELY have ANY clouds during the spring/summer months, except during the monsoon season. I've been in a lot of states, and I've never seen over 330 cloudless days anywhere else. And even on the days that there are clouds, they don't stay long before it is bright and sunny again.
Those figures sound too low for a 4.0. Ours is a 4.8kw and it is projected to produce 8640kwh/yr. and it tilts due West. It will be interesting to see how close the company's figure will be. I know this is the guaranteed output so we will see soon.

 

[Gonewild]

dress- In phx you loose some power do to high afternoon temps. As Leaffan says there are no late afternoon clouds.

 

[turbo2ltr]

So I'm trying to "reverse engineer" a solar lease from Solar City. I like to know how they make money so I know where my money is going.

They offer three options.
zero down lease, $59 lease payment but the payment has a 3.5% annual increase.
The partial payment lease is about $4k down with a $19 payment, no increase
or a one time payment of just under $6k.

This is for a 4.14kw DC system,which is probably a bit small (I had him quote a 5.1kw system as well)

So in order to see how they make money, I plotted out the payments over the 20 years and did an ROI analysis.

I found the biggest "fudge factor" is their calculated utility rate inflation. They quote it at 6% which to me sounds very high. I asked him to run his report with a 2% annual increase and he gave me one for a 4%. So that begs to ask the question why. Well it's because of the lease payment increase in the zero down option, it *requires* that the utility rate inflation be at least that much or you actually end up negative ROI after about 16 years.

He sent my a list of rate adjustments supposedly from APS and his comments about it are below (I haven't verified):

Below is the actual history of rate increases over the last 38 years sent to me from a Customer Service rep at APS. The link at the very bottom takes you to the APS website to view this chart directly. We came up with 6% based off the history of rate increases and more importantly on where we feel future rate increases will be over the next 20 years. APS will continue to sell less power because of solar, and other energy efficient methods along with greener construction of homes and buildings, so naturally APS will continue to raise rates as they lose profits. That is all explained in the article I left with you.

As you can see from below, there was a steady rate increase between 1972-1991. During that 19 years there was an average rate increase of 7.06%. Then from 1992-2004, there was a decrease of 1.32%, because the ACC (AZ Corporation Commission), who regulates utility companies, got involved to help make up for the steady rate increases the prior 19 years.

Over the last 38 years there has been a rate increase of 3.97% and an increase of 6.46% over the last 5 years. Another rate increase will happen in 2012 which should be close to the last rate increase a year ago of 12.99%. So technically, if you have been in your home for the past 7 years your rate increase would have been 4.6%...but keep in mind per the chart below, in 2007 when solar really started to take off there was a whopping 15.1% rate increase followed by the 12.99% in 2010.

Do you guys think 6% is a decent number or more/less?

The break even point for the second and third option is about 6 years, depending on the actual utility rate increase.

The lease numbers he quoted assumes a $1.60/kw rebate from APS.

The downside: their current install timeframe is 8-10 months but I'm really liking the one time lease.

spreadsheet..
https://docs.google.com/leaf?id=0B-DGAXnbchK0ODNjNzVlNzQtNTFhZC00MDliLThhNzYtOTBkYzJjYTc4ZGE1&hl=en&authkey=CODJqfAB

 

[turbo2ltr]

APS Rate history i was sent.

https://spreadsheets.google.com/ccc?key=0AuDGAXnbchK0dHpuQzN6bkNtT0hGcVBzTUJWQ3Jtemc&hl=en&authkey=CK2CxK4D

 

[SilverLeaf]

Just contracted to put in a 5.52 Kw System

24 SunPower 230 Panels
1 SunPower 6000 Inverter
1 SunPower Internet Monitoring
10 Guage Wire

They will install a string of 13 Panels at the top of the roof and 11 Panels in the next string.

The roof is a S-Tile Roof with a 20% pitch facing nearly due south.

Qualifies for a $1.75 per Kw Rebate from APS plus all the standard fed/state rebates.

Should cover 100% of my PRIME On-Peak usage. Off-Peak is billed at $0.55 (approx).

Any comments, suggestions would be greatly appreciated.

 

[Jimmydreams]

Just contracted to put in a 5.52 Kw System

24 SunPower 230 Panels
1 SunPower 6000 Inverter
1 SunPower Internet Monitoring
10 Guage Wire

They will install a string of 13 Panels at the top of the roof and 11 Panels in the next string.

The roof is a S-Tile Roof with a 20% pitch facing nearly due south.

Qualifies for a $1.75 per Kw Rebate from APS plus all the standard fed/state rebates.

Should cover 100% of my PRIME On-Peak usage. Off-Peak is billed at $0.55 (approx).



Any comments, suggestions would be greatly appreciated.

VERY nice!! You'll love it, especially out in the Arizona sunshine!! Make sure you get the "kiosk" link to your monitoring so people can see it and drool!!! :mrgreen:

 

[garygid]

Better to have the 24 wired as two strings of 12, I believe.