Poly vs mono and SMA vs Enphase

[cyph]

Based on the California Energy Commission report (http://www.gosolarcalifornia.ca.gov/...pv_modules.php) of real world test, at the same watt rating, the poly version of the panels by the same maker best the mono version each and every time. This seems to contradict the conventional wisdom that mono is more efficient. Furthermore, poly panels are better in low light supposedly and cheaper to produce. Is there a reason to pick mono panels?

I now have two homes (one with 5.04kw Trina SMA combo and one 5kw Canadian Enphase combo). Both are free from shades. I will compare the performance tonight after sundown to see if the enphase's supposedly better production in low light will allow it to eek out any performance gains over the SMA.

As a bench mark, the 5.04kw system for the past few days has averaged 31.5kwhr production a day.

[cyph]

The SMA system produced 31.07 and the Enphase produced 29.7. There's a 4.5 percent difference here. This is just by looking at the LCD screen of the envoy. The system hasn't been registered yet so I'll have to revisit this again after the system goes live and I can track the individual panel production.

[cyph]

I'll continue to have this conversation with myself.

It appears I have west side trees that I didn't think would affect my production, but apparently it does. At 5 PM, the Enphase system beats the SMA one by 1 kwhr. By 7PM, the SMA system is .8 kwhr higher. I suspect that I will be losing 5% production each day by by tree shade. Which means my decision to go with Enphase is a good one as it potentially be worse with a string inverter.

[russ]

I'll continue to have this conversation with myself.

It appears I have west side trees that I didn't think would affect my production, but apparently it does. At 5 PM, the Enphase system beats the SMA one by 1 kwhr. By 7PM, the SMA system is .8 kwhr higher. I suspect that I will be losing 5% production each day by by tree shade. Which means my decision to go with Enphase is a good one as it potentially be worse with a string inverter.

Look at the insolation at 5 PM & 7 PM - you are losing nothing measurable. On a site with no shade nearly your entire production will come in a window 5 to 7 hours long - the light before and after is meaningless for solar.

[Naptown]

Look at the insolation at 5 PM & 7 PM - you are losing nothing measurable. On a site with no shade nearly your entire production will come in a window 5 to 7 hours long - the light before and after is meaningless for solar.

Not necessarily. 5:00 is several hours away from sundown and tilt, and azimuth of the array's has not been mentioned or accounted for. Both can have an influence on production.

[cyph]

Look at the insolation at 5 PM & 7 PM - you are losing nothing measurable. On a site with no shade nearly your entire production will come in a window 5 to 7 hours long - the light before and after is meaningless for solar.

Unfortunately for me, from 5pm - 6:30pm, the generation is still part of the fat bell curve. The loss is still neglible and I'm not going to worry about it. I believe I am losing a full 25% of potential solar power after 5PM. The SMA system generates 6.19 kwhr after 5pm . So 25% of that is about 1.5-2 kwhr.

[craeay]

I'll continue to have this conversation with myself.

It appears I have west side trees that I didn't think would affect my production, but apparently it does. At 5 PM, the Enphase system beats the SMA one by 1 kwhr. By 7PM, the SMA system is .8 kwhr higher. I suspect that I will be losing 5% production each day by by tree shade. Which means my decision to go with Enphase is a good one as it potentially be worse with a string inverter.

Are the west side trees on the SMA unit or the Enphase unit?

[craeay]

Based on the California Energy Commission report (http://www.gosolarcalifornia.ca.gov/...pv_modules.php) of real world test, at the same watt rating, the poly version of the panels by the same maker best the mono version each and every time. This seems to contradict the conventional wisdom that mono is more efficient. Furthermore, poly panels are better in low light supposedly and cheaper to produce. Is there a reason to pick mono panels?

I now have two homes (one with 5.04kw Trina SMA combo and one 5kw Canadian Enphase combo). Both are free from shades. I will compare the performance tonight after sundown to see if the enphase's supposedly better production in low light will allow it to eek out any performance gains over the SMA.

As a bench mark, the 5.04kw system for the past few days has averaged 31.5kwhr production a day.

What type of roof is on your homes?

[cyph]

Are the west side trees on the SMA unit or the Enphase unit?

It's on the Enphase unit. The SMA is on a two story house which I think clears most of the trees. My roof is metal. It dents... unfortunately.

[russ]

Unfortunately for me, from 5pm - 6:30pm, the generation is still part of the fat bell curve. The loss is still neglible and I'm not going to worry about it. I believe I am losing a full 25% of potential solar power after 5PM. The SMA system generates 6.19 kwhr after 5pm . So 25% of that is about 1.5-2 kwhr.

Where are you? That is in no way possible - to lose 25% after 5PM

[cyph]

[

Where are you? That is in no way possible - to lose 25% after 5PM

My area is San Jose, CA. The sun here generates 20% of its power after 5PM (6 kwhr) and I lose about 25% of it to shade which is 1.5 kwhr. I didn't mean to say I lose 25% of my power after 5PM. 25% of 20% equals 5% loss of power.

Here is my solar bell curve: powersolar.jpg

[russ]

Apparently you have a west facing roof and lose a great part of the potential daily production - bad location!

[cyph]

It's southwest facing. Is 29-31 kwhr for a 5kw system below average in Northern California? The system is producing 850 this past month.

[russ]

Play with the Sharp calculator - it lets you adjust most things http://sharpusa.cleanpowerestimator.com/sharpusa.htm

Gives you an idea

[cyph]

Awesome calculator! It predicts that I get 18.5 kwhr on average. With E6 it should cover 86% of my bill. The weird thing is that with a HELOC it predicts 5.6 year payback whereas cash purchase is 6.8 years. I'm not sure how it figures that.

In either case, both systems are handily beating the estimate. I expect 28 kwhr average for eight months and 15 kwhr daily for four winter months would still exceed the 18.5 kwhr daily by a healthy margin.