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

[silversaver]

Save your money with string inverter, you might have less roof spacing now.....

[wwu123]

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.

Not really that much of a mystery when you think of all the dense material (thermal mass) in your wall studs and floors has been baking in the heat all day and holds way more heat energy than just the "light-as-air" air in the room. If you merely replace the hot air in the room quickly, the warm walls and floors will quickly start warming up the cooler inside air once again. For example, if you install a whole-house fan, a properly sized one can exchange out the entire volume of air in your house and attic with cooler outside in in 3-5 minutes. But that's not going to cool down your house if you then shut it off - you have to keep running it for a few hours to exchange new cool outside air continually that will soak up the heat slowly from the walls and floors.

Ever go to one of those newer "hot stone grill" teppanyaki places where they give you a superhot stone and some raw slices of steak and shrimp? The hot stone is your house after a long summer day, cooking everything coming on top of it including the air and the meat for a good 30 minutes (the poor raw shrimp being the analogy for you cooking inside your hot stuffy house...)

[J.P.M.]

I figured out how to turn on Shadows in Sketchup (this program is pretty damn powerful and useful!) and just with a rough box to represent the neighbor's 2 story house (I guesstimated 23' to the roof, could be less) but it looks to confirm what the guy found today using the SunEye...

10:00 am


1:00 pm


3:00pm

Nice . Sketchup does seem quite useful.

A thought or two:

To get a perhaps better idea od garage location, heights, etc, Go out some day and measure where the garage shadow falls on your south roof. Then, vary the dimensions the software uses until you get a match in 2 dimensions. If the software adjusts for lat./long. and date - solar time vs. civil time, you might get a better guesstimate.

Looks like your south roof is not super good. Any thought to placing south facing panels on the north face of the northern section of your garage ? - that is, have panels facing south on an otherwise unobstructed north facing roof ? South face of garage may have some possibilities too. Just sayin''.

[JCP]

Can always move to a new one, or build a second story on top of your house.

[HX_Guy]

If you got that much of shade, nothing can help you......

[silversaver]

If you got that much of shade, nothing can help you......

[HX_Guy]

I figured out how to turn on Shadows in Sketchup (this program is pretty damn powerful and useful!) and just with a rough box to represent the neighbor's 2 story house (I guesstimated 23' to the roof, could be less) but it looks to confirm what the guy found today using the SunEye...

10:00 am


1:00 pm


3:00pm

[Ian S]

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.

OK, I can see where that could be an issue. I'm surprised the one guy didn't see any problem. Maybe if you asked nicely, your neighbor would lop off his second story.

[J.P.M.]

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.

Everybody's got internet monitoring. Nothing special.

[J.P.M.]

See comments in bold:

Equal size systems produce the same annual output - initially and for some yrs. down the road. I'd suggest A more important efficiency to consider may be PRICE or COST efficiency, including the cost advantages gained by conservation efforts which can first of all lower the bill and then also reduce the optimum size system, thus making possible a less expensive panel with a lower area efficiency that will now fit on the smaller roof.

The lower yearly degradation of S.P. is acknowledged. It can and is being dealt with, but really needs a life cycle cost analysis to be done correctly, and is probably not amenable to blanket statements without gross oversimplification of the type necessary for this forum. One way to consider such matters is figuring out the "levelized cost of electricity". PITA, but it puts things on more or less equal footing, or can do so, depending on smoke/mirrors of perpetrators.

[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.

[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.]

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.

[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.]

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.