AC or DC Solar Panels in Extreme Heat?

[Taylori]

Doesn't seem like there is any consensus among the club here on which setup would work better. I think however if you posted the pricing for each system, AC SunPower or the string CS panels you would get more of a consensus. I'm curious to the responses you will get when you reveal the difference in price.

Sorry, I've been off my computer for a few days. I am still working with the salesmen trying to get an apples to apples comparison. It's like herding cats. As it currently stands, SunPower's system costs $54,932, and the Canadian Solar system costs $57,972, but the cost of the system is of little interest to me because I plan to lease it. The SP lease is for 20 years, whereas the CS system is for 25 years. The SP system is engineered to offset 85% of my electric bill, wheres the CS system's offset is 96%. (why the big difference?) My concern is how much will I save in the first 10 years, since I am an old man and will either die or sell within that time span. 10 years out, with nothing down, 0% annual increase in lease payment, and a 6% annual increase in the electric bill (California's 10 yr. average is 6.7%), I calculate cumulative savings with the SP system at $21,988, and $20,918 with the CS system. That is close enough for me to look at other factors, like which system is likely to be the least trouble free in the extreme heat of the desert. Thus my initial question. From the responses I've received so far, I'm guessing that the jury is out. I have done a lot of online research, and I haven't found the answer. That research though has convinced me that SunPower has the superior panel; at 20%, it is definitely the more efficient panel. The proposed SP system would take up far less space on my roof. I'm trying to get an explanation now as to why the 2 offsets are so different . . .85% and 96%. Surely there is an optimal offset. Warranties, incidentally are identical, at least as far as I can tell. I would appreciate any thoughts as to which direction I should go.

[Taylori]

This is a good point. I was also interested in how much space they take on your roof, as SunPower claims that their panels take up less space, so you can add more/put more.

I don't know the square footage, but the SP system with the inverter in the garage takes up dramatically less space on the roof than the CS system with a microinverter inside each panel. . . 32 panels versus 49 panels. See my response to SoCalsolar.

[Taylori]

My guess is a 6-10 panel difference ( 8-12k system size) they seem to spin their meters pretty hard out in Palm Springs and the "AC" panels are a touch over 19% efficient compared to Canadian S. which are between 14.6%-almost 15.8%. If space is the major concern SP has a panel that is a smidge over 20% efficient but those are not "AC" just regular "DC" but they are half the cost of the "AC" panels. Still waiting for the cost of the "AC" panels I want to see the talking heads explode.

See my earlier responses. The difference is 17 panels. The SP system is 32 panels and the CS system is 49 panels, but there is a big difference in electrical bill offset. See my earlier response to you.

[SoCalsolar]

Taylor just a few thoughts

Taylor looking back over your posts you mentioned using 32 SP AC panels in a lease compared to 49 CS panels. As far as I am aware the SP AC panels only come in 240w or 225w and they are not offered by SP through their lease. Now your lease could be a third party lease CPF, Sun Cap, etc. However using those panels rarely saves you any money in CA, not to mention if I use 32 240w panels i get a system size of about 7.7kW. If I then use 17 more (49 CS panels) and that system only eliminates 10% more of your bill then the CS panels would need to be about 200w each? Does this sound right? It also sounds like most of your 21k in savings comes from anticipated SCE rate increases of 6% a year? Just so you are aware in some leases the lessor will try to attach the terms of the lease to the estate of the lessee upon their death. Is the lease payment lower than your current payment? If so by how much? Let me know the size of each of the panels. These days there are usually more financially sound ways to go solar than a month to month lease but every case is unique. The more info you give the better the advice or suggestions you will receive.

[SolarJoe]

The Panels should be fine it's the micro-inverters that's going to be problem, do your research and find micro-inverters that works better in heat.
Hope this help

[Taylori]

Taylor looking back over your posts you mentioned using 32 SP AC panels in a lease compared to 49 CS panels. As far as I am aware the SP AC panels only come in 240w or 225w and they are not offered by SP through their lease. Now your lease could be a third party lease CPF, Sun Cap, etc. However using those panels rarely saves you any money in CA, not to mention if I use 32 240w panels i get a system size of about 7.7kW. If I then use 17 more (49 CS panels) and that system only eliminates 10% more of your bill then the CS panels would need to be about 200w each? Does this sound right? It also sounds like most of your 21k in savings comes from anticipated SCE rate increases of 6% a year? Just so you are aware in some leases the lessor will try to attach the terms of the lease to the estate of the lessee upon their death. Is the lease payment lower than your current payment? If so by how much? Let me know the size of each of the panels. These days there are usually more financially sound ways to go solar than a month to month lease but every case is unique. The more info you give the better the advice or suggestions you will receive.

Boy, am I ever embarrassed! Your response caused me to look back at my initial post, and I stated the situation exactly backwards! Although SP sells AC panels, the panels they quoted are DC. It is the Canadian Solar panels that are AC, i.e., panels with a microinverter built inside each panel. I couldn't be more embarrassed by that gaffe, and I apologize profusely. I will answer your questions as best I can, as you sound like someone who might truly help me make my decision.

The lease is directly through SP, whereas the CS lease is through a 3rd party. In both cases the lease is assumable by a purchaser of my house at any time throughout the duration of the lease. I will have to enquire as to what happens upon my death. Thanks for the heads up. My average monthly payment now without solar panels is $419/mo. (gasp!) That is why I am looking into a solar system. Whether I go with the DC panels or the AC panels, the savings are substantial. Right now I am up to my ears with different proposals: $0 down, 0% annual increase in the cost of the lease; $2500 down, 0% annual increase in the cost of the lease; $0 down, 2.9% annual increase in the cost of the lease; and $0 down, 3.9% increase in the cost of the lease. The latter 2 options clearly save me the most money in 10 years, which, because of my age (74), is all the further out I am looking. But I am concerned as to how attractive taking over the lease would be to a potential buyer of my home. Clearly, the 0% annual increase options would look the more attractive, especially as each year passes, but those are the options that would cost me the most over the next 10 years! As of this morning, and because of my incessant questions, SP is going to do a site analysis at no obligation to me next Thursday, so they can present me with a "best fit" proposal. They should have done that in the first place! I've asked the CS salesman if they would like to do the same thing, and I haven't received a response. Thank you for looking closely at my situation. I do appreciate it. If you have any more questions I would be happy to answer them, although I will probably have better data after the site survey next Thursday.

[SoCalsolar]

How did the site survey go?

Usually the site survey happens after the contracts are signed it saves the install company from spending more money than the sales guy gas. You can either Private Message me or post your leases minus any personal information and I can give you some very specific feedback regarding the terms and some pitfalls.

[russ]

The Panels should be fine it's the micro-inverters that's going to be problem, do your research and find micro-inverters that works better in heat.
Hope this help

Pardon? Where does this tidbit come from and how much better?

[inetdog]

Pardon? Where does this tidbit come from and how much better?

Well, I suppose that just as there are some string inverters and CCs that work better at elevated temperatures than others (not better than at normal temperatures, but degrading less), there may well be a brand among the large number (2?) of major microinverter manufacturers that has done better than all of the rest.

Now if only they would produce directly comparable specifications, the choice should be easy.
But a difference of a couple of percent at high temperatures may not be the deciding factor given other things like cost, reliability, etc.