Help deciding on which panel/company

Hmm, prices sound to close to be a coincident. Just thinking.out loud.
Partial shading? Partial shading kills series wired arrays.

I'd be more concerned about other aspects of the system such as the inverter choice. One feature that Sunny Boy now offers on some inverters provides a small amount of backup power for grid-tied systems. In general, grid tied systems don't provide any usable power to the site when the grid is down.
As far as the panels, I'd consider snow loading where you are and whether any of the panels handle that better than the others. Some may allow snow to slide off better maybe due to frame construction??? The sooner the panels are clear of snow the sooner they'll start producing.

Solarworld panels are well regarded by our local Solarize installers.
My understanding is that the micro inverters will only help if you have instances where some panels are shaded while others are not. If there is never shading, or if all panels are shaded simultaneously I don't think they are needed.
Be patient on response, we have some resident experts here that may reply.

In my opinion, avoid microinverters unless you have shading issues, Bolted under a panel on a roof is tough place for electronics. Enphase had issues with early models not surviving and even their new units are not proven over the long haul. With a 5/12 pitch you will have occasional snow buildup issues, microinverters are nice as usually the top of array is exposed so you get some generation until the panels melt off. If you are going with a 10 KW (make sure that you don't exceed a utility threshold as many utilities treat you differently over 10 KW) I would go with two 5KW central inverters and make sure they have dual MPPT inputs, that way you can configure the array for 4 strings each on a MPPT so that if part of the array is covered, the other strings will run. Central inverters usually live in far cleaner cooler environments and are a lot easier to change out if there is an issue. If you get the SPS power supply on the Sunny boys you would have 3000 watts of backup power from two outlets if you have two inverters.

The trade off is central inverters need more design skills than microinverters, microinverters are plug and play while string inverters requires some code skills to do the calculations

Solarworld panels seem to have good rep, I would avoid the other panel lesser name poly panels. Mono panels have the longest life that's been proven in the field. If you have plenty of room on the roof no need to go with Sunpowers, they are really only worth it if you are short on roof space. One caveat on the 320 watt Sunworlds is you want a microinverter sized for the full panel output. I think Enphase only makes 250 Watt units that will take 300 watts input but you only get 250 watts out. I don't believe in overloading inverters, running anything at 100% for extended periods is not great for longevity. Be aware in New York on a bright cold days with snow on the ground your panels will exceed your nameplate, I have seen 10% over on some occasions. I would even slightly oversize the central inverters but sticking with nameplate beats the Enphase concept of clipping the input.

A couple of last things. Make sure what code cycle you have to meet, the latest electrical code requires that the panels can be made safe (disconnected) within a short distance of the panels. With central inverters you may need an remote automated disconnect and a additional conduit up to the roof for a signal wire. My understanding is that microinverters do not need this. Midnight Solar makes one of these disconnects and I expect others do http://www.midnitesolar.com/rapidShutdown/rapidShutdown.php
Second thing is don't go cheap on surge suppressors, I had Deltas (the cheap ones most installers use) and lost an inverter. Midnight Solar makes a SPS with much lower clamp voltage. With a SPS a surge will go to ground and your electronics should survive but a Delta will clamp at too high a voltage to save the electronics but might keep them from burning. I would put a SPS's at the combiner box on the roof and one at the input and output of the inverters.

I have two Fronius inverters, one got zapped by the utility under warrantee and they had a new unit at my house in two days. The other is humming along fine. Sunny Boys have good rep. but I havent used one.

Shading can be quite deceptive, from trees to shade cast by puffy cumulus clouds passing overhead as their shadows rolls across the panels. Shade on one panel in a string will knock the whole string down. I have micros, and a typical "sunny" summer day with cumulus clouds still can easily reduce production by 20%. I don't know what the impact would be if had strings of panels.

Winter shading from trees ... the low winter sun angle will bring shadows from trees a long ways off. December sun for me gets down to 19* at noon, and trees 60' high need to be about 175' away to cast no shadow, and even further away as the morning sun climbs to 19* and then sets again in the afternoon. At 15* trees need to be 230' away.

There is a globe device your installer can use at the panel location to determine shading potential.

There are a couple of handheld systems that can predict shading quite accurately. They don't figure out how much snow will stick to the panels. No real difference between solarworld 250 and 320 modules. In theory larger panels may slightly reduce the amount of mounting parts.

How do you get up there to say, replace a microinverter? The roof is covered with panels.

Coincidentally, we're getting a visit from a solar company tomorrow morning.

Good Q on replacement of micros. As you see from my picture, my panels are ground mount and micro accessibility and snow clearing are very easy. Micros also excel in snow cover because as each panel clears it produces power and does not knock down other panels. I always clear snow from my panels; letting them melt can be a long wait.

Ground mount would be great, but I don't have the space. What do you do when you have to replace something like a microinverter when it's on the roof, and you can't get any footing on 'terra roofa"?

With a 5/12 pitch, a roof ladder with hooks on the top that goes over ridge will probably work to get access but it definitely would be a PITA to have to pull a panel from a ladder and definitely not OSHA. To me the safe approach is set up a scaffold at the base of the panels and then remove the lowermost panel below the bad one then work up using the racking roof mounts to stand on until the bad panel is reached.

One positive in that situation is unlike a string inverter, only the bad panel needs to be covered while with a string of panels, all of them need to be covered to work on any one of them. Having disconnected a string once with the sun out and seeing the resultant arc in the connector, I sure wouldn't do that again. I now cover the panels and do my final connections at night with a headlamp.

Good thread. The three good things I've learned from this post so far, consider

• snow shading as well shading from nearby objects
• access issues when using microinverters
• how to service an array that's producing power

I just got a quote from a local solar place who's been in business a while.

16 LG panels, 4.48 kW, estimated to produce 4,614 kWh/Yr for my setup, SunnyBoy inverter, $19,268 before NYSERDA rebate and federal tax credit.

She said something about the panels having 'bypass diodes' to help with shading, but I'm not sure what that means. I like the concept of an inverter located in the house for weather protection and serviceability though.

I'm still a leary about putting them on a metal roof, but she says they do it all the time.

They want $500-1000 before they actually get an 'engineer' working on it. I'm surprised they can come up with a quote without that-must be enough profit in it.

velvetfoot said:

How do you get up there to say, replace a microinverter? The roof is covered with panels.

Click to expand...

In my case, I mounted the microinverters along the rails nearest the edges of my array which is 2x10 (rows x columns) in portrait and has 3 rails under each panel. If I need to get to a microinverter, I believe I can technically do it without removing any panels. Your average hang'em and drive installer probably wouldn't take the time to mount the Enphase micros where you can reach them.

Checking today at noon, my upper row of inverters runs ~10°F higher temperature than the lower row on a 93° summer day.

Seems like a good deal to me.
We're not eligible for the NYS tax refund.