Looking to go solar...everything looking good, am I missing something?

[Ian S]

Ian, I got some clarification on the 11.2 SunPower vs the 12.24 Canadian Solar.

With the SunPower, they are figuring that they can fit all the panels on the south facing slopes while with the Canadian Solar, and needing quite a few more panels, some of them would have to go on the east facing slope. Because of that, they are saying that they would need 12.24kW of Canadian Solar panels to produce the same power as 11.2kW from the south facing SunPower panels. Does that make sense or are they feeding me some BS?

There's also another kink in the quote...the SunPower panels are E19 panels which I guess are discontinued, and also don't include internet monitoring, it would require a separate kit...is that right? Newer E20 panels, which would cost more, apparently include the internet monitoring?

That could certainly explain the difference in output. In addition, those east exposure panels won't contribute much to on-peak production if you were to go with the TOU rate plan. I really don't know about the difference in internet monitoring between E19 and E20 but it's something you absolutely want to have. I can't imagine not having it myself. I wish Rich (Naptown) would drop by as he probably knows the most about Sunpower around here. I would also just say that no matter what panels you wind up going with, they will likely be discontinued within a year or two. Mine were only installed two years ago and seem like virtual relics at 230 watts per panel. LOL!

[HX_Guy]

Haha good point about the discontinued stuff. And I agree, the internet monitoring is an absolute deal breaker for me. I love that kind of stuff...I check my Nest thermostats all the time. SunPower is starting to look better as we could have more kWs facing the south direction.

[HX_Guy]

We'll this is turning out to not be quite as rosey as I initially thought, the shade issues seems to be much bigger.

The guy who was pushing SunPower and the micro-inverters(the brand is Solar Bridge BTW) came by and did measurements and a shade analysis himself and according to him, we have full shade on the majority if the south roof in Nov/Dec/Jam so he recommended not putting any panels there at all. So with that, filling up all south facing non-shades parts AND the east facing side, we could only get about a 9kW system with the bigger cheaper panels like Canadian Solar. Even with the 327W SunPower panels, we wouldn't get full 100% coverage. Incidentally, and seems like BS, be said with the 240W micro-inverter panels we could get full coverage because the panels are so much smaller and he can more/different layout.

That's at least how I remember it, waiting on actual quotes. I'm pretty skeptical on the shade thing though, I don't recall the neighbors 2 story house shading out house that much and the other guy's analysis said otherwise. I may just wait until winter and see for myself before going forward.

[silversaver]

Look for any shading around your house, you can find out if there's any shading taking palce. I know I have late shading from tree and chimny, they are easy to spot. If the shading were later afternoon or early morning, then don't worry about it. Solar production mainly from 9am to 3pm to 5pm (Winter and Summer).

[HX_Guy]

There is zero shading now but there is a 2 story house literally 10ft to the south of our house and they are saying that in the winter months with the sun being south lower in the sky it will shade our roof partially.

[Ian S]

There is zero shading now but there is a 2 story house literally 10ft to the south of our house and they are saying that in the winter months with the sun being south lower in the sky it will shade our roof partially.

If the guy has the specialized equipment and knows how to use it, he should be able to predict shading quite well. But you apparently have different outfits telling you different things which presents a problem. Maybe press the other guy on why he feels shade won't affect winter production. From the original image you shared, you've got panels right down to the gutter on the south roof. It may well be that with the other house so close, winter shade would be cast on part of the panels next to the gutter and that would be bad. What about west facing roof?

[wwu123]

I get pretty bad shading on my south-facing array in those winter months as well, almost no production after 1 pm for three months. But I put them there anyway because the production is lowest in the winter due to cloudy weather and low sun angle anyway, so you're losing out then but gaining best productivity during the summer months otherwise. If your utility's TOU plan has peak summer pricing, it works even better if you can use excess summer peak production to offset off-peak consumption in the winter.

Installers sometimes have tools that can do a shading survey with tools that photograph the entire horizon 360 deg and can tell exactly what days you'll be shaded. They can then plug that data into models of production and tell you whether you will get more production overall from those south roofs or from the east ones. If they have more sophisticated models that include TOU utility pricing, they could calculate whether the TOU pricing will make the south roof still advantageous from a $$$ standpoint even if they produce less than the east roof.

[J.P.M.]

Interesting, I have the same issue. In winter time here in socal we may have big fluctuations in outside temp where it may get into 70's during day but then cool at night down to 50 or even lower. Still what happens in my house is the second floor gets hot at night while it's cold outside. And the attic temp is cool (I have a remote thermometer). If I cool it down either by AC or by opening a window and whole house fan it will cool temporarily but after I shut the window or turn off AC after a while the second floor is hot again. I don't understand where the heat is coming from. Haven't heard this term "thermal mass" before, i'll have to look that up and see what that means. My house is a stucco house as I suspect the AZ house is as well.

Houses can be dynamic creatures when it comes to heat flow and w/out knowing the particulars it's hard to predict/analyze. However, I finally made some sense of this a long time ago by visualizing heat "leaking" through exterior walls, being stored there by the building materials, insulation, etc. while flowing inward in sort of wavelike fashion, reaching the interior surface some time (hours) later. Years later I learned this was all part of the concept of thermal lag, or more accurately called building thermal capacitance or some such name and related to the building time constant which in very over simplified form is the effective building thermal mass divided by the overall building heat loss coefficient. Somewhat analogous to capacitance and time constant in an electrical circuit.

[HX_Guy]

The problem with the TOU stuff is that the local electric company separates that so you can't apply power produced during TOU hours to non-TOU hours.

I took a current photo showing the relation of the neighbor's house to our southern facing roof, not sure if it can really tell us anything.
Here's the photo from the east, looking west.



I did find this good aerial photo from Nov 6th but it looks like its earlier in the morning since there is a shadow on the back fence (meaning sun is rising in the east). I really need to know end of December anyway.

[Ian S]

I get pretty bad shading on my south-facing array in those winter months as well, almost no production after 1 pm for three months. But I put them there anyway because the production is lowest in the winter due to cloudy weather and low sun angle anyway, so you're losing out then but gaining best productivity during the summer months otherwise. If your utility's TOU plan has peak summer pricing, it works even better if you can use excess summer peak production to offset off-peak consumption in the winter.

Yes, we have peak summer pricing on TOU but generally rely on winter production to bank credits for the summer where solar usually falls far short of our needs. My trueup is in early December, and in the following 3 months even with inferior insolation, I will typically bank 600 or so peak kWh which come in handy on those 115+F days in late June early July.

[J.P.M.]

For some reason, the annual production for the LG system is somewhat higher than expected compared to that expected from the Hanwha system. The nameplate power of the Hanwha system is 42 X 240 = 10.08 kW; that for the LG system is 42 X 260 = 10.92 kW.
(10.92/10.08) X 16564 = 17944 which is 177 kWh less than the 18121 given. Since it was the same guy doing the estimating, I wonder why that is. Maybe the LG panels have less deterioration or just better performance wrt nameplate? Dunno.

I found something similar in running SAM for my area. According to that design tool, an LG300 equipped system will produce slightly more per D.C. Watt on a yearly basis than a S.P 327 equipped system in the same orientation and service. The differences were small enough however, that I figured them within error margins.

[J.P.M.]

Jon, same exact issue here. I always find myself wondering how in the world is it hotter inside the house than outside if I cool the inside but then after shutting off the A/C, the temp in the house starts to increase even though the outside temp is lower.

See other post. The heat may be "leaking" through the walls and takes awhile to get to the interior.

[J.P.M.]

If you want a 25 year warranty it will cost more any item with better coverage and build will. The smaller size helps on a lot of roofs that have limited space. As far as will the warranty and service be around is yet to be seen. You can say that about any product made cars, Home builders anything. I wanted the warranty and got the extended 20 year on the inverter. All anyone can due is research and try to get the best product, installer, warranty for the best price. Everyones comfort zone is different.

Pay your money, take your choice and take your best shot. It's a free country and opinions vary.

[silversaver]

The problem with the TOU stuff is that the local electric company separates that so you can't apply power produced during TOU hours to non-TOU hours.

I took a current photo showing the relation of the neighbor's house to our southern facing roof, not sure if it can really tell us anything.
Here's the photo from the east, looking west.



I did find this good aerial photo from Nov 6th but it looks like its earlier in the morning since there is a shadow on the back fence (meaning sun is rising in the east). I really need to know end of December anyway.

Base on the photos, looks like your will have shading issue during Winter. If you are using 2 inverters+, then choose the one with dual MPP trackers. At lease you can put those possible shade ones in same string through one MPP tacker. Take a look at SMA TL-US series.

[J.P.M.]

your milage may vary but I almost never get an extended warranty. The terms are usually crappy and the price of the products covered usually goes down over time, meaning replacement costs is often cheaper than repairs.
Put the money you would have put into said extended warranty for your :

• car
• cell phone
• TV
• Fridge
• Computer
• Stove
• microwave
• washer / Drier
• inverter
• etc etc

all into a savings account.
YMMV

If people had any idea how much pure profit is tied up in extended warranties, and thus an indication of what a poor deal the fear mongering in the peddling of those bogus instruments engenders, toilet paper sales would go through the roof. From the inside, many years ago: they are a rip off.