SunPower vs LG System?

[J.P.M.]

Happy Holidays to you too J.P.M.! I guess after 4 1/2 years, I find myself kinda taking my solar for granted. I haven't bothered cleaning the panels for a year especially since the new HVAC system has put my electric consumption back to the point where my trueup (which occurred today) leaves hundreds of peak kWh's to be compensated @ a measly $0.029/kWh. So I'm in a sweet spot where I don't pay for any peak kWh at all throughout the year and saving some off-peak kWh's @ ~$0.07/kWh doesn't seem worth the risk to life and limb that I take in going up on my roof for regular cleanings. I still plan to put some bird spikes along the upper panel edges but there are a number of other outdoor home maintenance tasks that have jumped to the top of my winter to-do list!

With regard to the panel degradation, I agree that the warranty would be hard to enforce and in any event, allows for much more degradation than would probably ever happen. My point was that the degradation specification for SunPower panels is superior to other panels even high quality ones like LG. Assuming we can trust such specs from any manufacturer, the difference in energy produced per watt can be significant over the lifetime of the panel system - possibly amounting to between 5 and 10%, perhaps more depending on the difference in spec values of degradation rate and what's considered the life of the product. The degradation occurs both initially and over the long term. LG brags about improving their Mono X2 initial LID (light induced degradation) from -3% to -2% and their long term degradation from -0.7% to -0.6% per year but SunPower specs no initial LID and a -0.25% per year long term degradation rate. Now, can such superior performance over the life of the panel fully offset the higher initial cost of the SunPower panels? Perhaps not but it certainly makes them more competitive and, IMHO, worth considering at least.

Meanwhile, time flies: only 16 months until my buyout date!

Thank you. It seems you had a horseshoe in you butt he day you signed that lease.

I'm not real trusting of most claims on performance/degradation, especially when verification is next to impossible which seems to me to remove most of the consequence of getting caught making unverifiably optimistic claims. But, I,m probably more skeptical and cynical than most.

As for S.P. and their warranty, first off, a lot can happen in the first 6 months after mfg. Then, item 2a of the published warranty and the S.P. definition of minimum peak power contained therein would seem to me go a long way to covering their butts for any light induced (burn in) degradation.

[SunEagle]

SunPower now has AC panels (essentially their panels with their own micro-inverter stuck on the back). This is your solution if you want to use one of their 300 watt plus panels. For myself, I had limited roof space (well enough for 40-ish panels anyway) to generate my 13000 KwH/year needs, so I went with SunPower AC panels with their 345 watt panels. The warranty and less degradation had to be weighed with the current cost of electricity ($0.20/kwh) and it's future cost, the length that the panels and micro-inverters last, the drop in cost for panels over time, compounded interest for the extra spent over time, federal and state credits, SRECs etc.

For my state and tax bracket, I got a 30% reduction in the 1st $35,000 dollars, 1% loan for 10 years for the 1st $35,000 dollars, 30% federal credit for the full cost, plus SREC payments for 10 years. Depending upon actual production (system is new), and the average price of SREC payments, breakeven point for me is 1 to 3.5 years.

As for Micro-inverter vs string inverter, I feel that even though micro-inverters add more points of failure, a failure only affects 1 or 2 panels, not the whole system. String Inverters have a shorter lifetime, and don't accommodate shading. While the power optimizer solution is more reliable than micro inverters (I'm an electronic engineer) on paper, Solaredge is a smaller company, and thus there is some risk there, and have a lot less # of units out on the market than say, Enphase, and thus have less field experience with them. In addition power optimizers, while dealing with shading (and better than Enphase micro-inverters, not sure about the rest) also still need a string inverter, so you lost that advantage. But of course YMMV.

I'd argue that all you really need is to figure your breakeven point, and everything after that is gravy!

Edit:
Also, one other item harder to calculate (because you can't always get the numbers from the install company) is the cost of installing less higher power panels vs more lower power panels) to get the same effective power, and the increase of failure when you add more panels vs less for either the micro-inverters or string inverters.

I would be hesitant to go with SunPower based on some of what I see in the news about them shedding 1/4 of their staff and cutting costs.

[Ian S]

Ian: First, Happy Holidays. Where/How Ya' been?

Next: I suppose I'd want to have some numbers to verify any performance suspicions I may have. How does one identify annual degradation in the field ? How does one measure it ? All panels in an array or just some ? Without micros, how to determine which ones ?
Who pays the freight to the testing site ?
Who pays what if any of the product is found to be within spec?
As for aesthetics, I'm not sure which if any, panel mfgs. consider appearance to be a warrantable product feature.

Happy Holidays to you too J.P.M.! I guess after 4 1/2 years, I find myself kinda taking my solar for granted. I haven't bothered cleaning the panels for a year especially since the new HVAC system has put my electric consumption back to the point where my trueup (which occurred today) leaves hundreds of peak kWh's to be compensated @ a measly $0.029/kWh. So I'm in a sweet spot where I don't pay for any peak kWh at all throughout the year and saving some off-peak kWh's @ ~$0.07/kWh doesn't seem worth the risk to life and limb that I take in going up on my roof for regular cleanings. I still plan to put some bird spikes along the upper panel edges but there are a number of other outdoor home maintenance tasks that have jumped to the top of my winter to-do list!

With regard to the panel degradation, I agree that the warranty would be hard to enforce and in any event, allows for much more degradation than would probably ever happen. My point was that the degradation specification for SunPower panels is superior to other panels even high quality ones like LG. Assuming we can trust such specs from any manufacturer, the difference in energy produced per watt can be significant over the lifetime of the panel system - possibly amounting to between 5 and 10%, perhaps more depending on the difference in spec values of degradation rate and what's considered the life of the product. The degradation occurs both initially and over the long term. LG brags about improving their Mono X2 initial LID (light induced degradation) from -3% to -2% and their long term degradation from -0.7% to -0.6% per year but SunPower specs no initial LID and a -0.25% per year long term degradation rate. Now, can such superior performance over the life of the panel fully offset the higher initial cost of the SunPower panels? Perhaps not but it certainly makes them more competitive and, IMHO, worth considering at least.

Meanwhile, time flies: only 16 months until my buyout date!

[miracj]

In regards to a central inverter vs microinverters, of course, I guess that would not be an option for me if I decide on S.P. 360W panels. But in general, besides part of my roof getting into shade during part of the day (depending on the season), isn't scalability also another advantage of the micro-inverters? Namely, if we add a couple of Electric cars down the road and want to add more panels then?

SunPower now has AC panels (essentially their panels with their own micro-inverter stuck on the back). This is your solution if you want to use one of their 300 watt plus panels. For myself, I had limited roof space (well enough for 40-ish panels anyway) to generate my 13000 KwH/year needs, so I went with SunPower AC panels with their 345 watt panels. The warranty and less degradation had to be weighed with the current cost of electricity ($0.20/kwh) and it's future cost, the length that the panels and micro-inverters last, the drop in cost for panels over time, compounded interest for the extra spent over time, federal and state credits, SRECs etc.

For my state and tax bracket, I got a 30% reduction in the 1st $35,000 dollars, 1% loan for 10 years for the 1st $35,000 dollars, 30% federal credit for the full cost, plus SREC payments for 10 years. Depending upon actual production (system is new), and the average price of SREC payments, breakeven point for me is 1 to 3.5 years.

As for Micro-inverter vs string inverter, I feel that even though micro-inverters add more points of failure, a failure only affects 1 or 2 panels, not the whole system. String Inverters have a shorter lifetime, and don't accommodate shading. While the power optimizer solution is more reliable than micro inverters (I'm an electronic engineer) on paper, Solaredge is a smaller company, and thus there is some risk there, and have a lot less # of units out on the market than say, Enphase, and thus have less field experience with them. In addition power optimizers, while dealing with shading (and better than Enphase micro-inverters, not sure about the rest) also still need a string inverter, so you lost that advantage. But of course YMMV.

I'd argue that all you really need is to figure your breakeven point, and everything after that is gravy!

Edit:
Also, one other item harder to calculate (because you can't always get the numbers from the install company) is the cost of installing less higher power panels vs more lower power panels) to get the same effective power, and the increase of failure when you add more panels vs less for either the micro-inverters or string inverters.

[J.P.M.]

It's not so much the warranty with regard to degradation, it's that the degradation spec itself is better and, over time, SunPower panels will produce more energy than panels with a higher degradation rate. That better performance will offset at least some of the initial price premium.

Ian: First, Happy Holidays. Where/How Ya' been?

Next: I suppose I'd want to have some numbers to verify any performance suspicions I may have. How does one identify annual degradation in the field ? How does one measure it ? All panels in an array or just some ? Without micros, how to determine which ones ?
Who pays the freight to the testing site ?
Who pays what if any of the product is found to be within spec?
As for aesthetics, I'm not sure which if any, panel mfgs. consider appearance to be a warrantable product feature.

[musklover]

I agree with Ian...I got my panels from SunPower and have had no complaints. However, I am based in Colorado so the tax credits might be different? I got 30% federal tax credit and I get rebates from my utility company. Unfortunately, utility companies have started charging higher utility rates for those who have solar panels.. damn them!! > monopolistic companies...
So I would definitely look into that before getting solar. I just the info on this for California: https://www.solarpowerauthority.com/home-solar/ca

[Ian S]

The degradation warranty is something I would imagine would be very difficult to warrant new panels. You would have to take the panel off of your roof, send it back to the manufacturer, and let them test it. If it still is within spec, you just wasted a couple hundred bucks in shipping.

It's not so much the warranty with regard to degradation, it's that the degradation spec itself is better and, over time, SunPower panels will produce more energy than panels with a higher degradation rate. That better performance will offset at least some of the initial price premium.

[littleharbor]

Another view, Sunpower brown cells (2).jpg

[littleharbor]

Sunpower brown cells 2 (2).jpg Here's something to keep an eye out for with Sunpower modules,

http://guntherportfolio.com/2013/03/new-sunpower-solar-cell-discoloration-anomalies-at-the-photovoltaic-demonstration-project/

I've had some Sunpower Modules with this anomaly. If your rooftop system were clearly visible these "browned out" cells would be pretty butt-ugly for all to see.

[emartin00]

JPM makes some excellent points. Failures of panels is extremely rare these days. If they do fail, it's usually early on, due to manufacturing defect, and that is what the warranty is for.
The degradation warranty is something I would imagine would be very difficult to warrant new panels. You would have to take the panel off of your roof, send it back to the manufacturer, and let them test it. If it still is within spec, you just wasted a couple hundred bucks in shipping.

I have no problem with Sunpower if you need that efficiency. But as many others have said, you can get the same power output significantly cheaper from a number of reputable companies.

[J.P.M.]

FWIW, I own a S.P. system, but my choice had nothing to do with economics. Long, boring story. If it had, I could have gotten equal or better performance for about a buck a Watt less before tax credit.

I've monitored ~ 100 system installs for my HOA and keep track of performance for several of them. When adjusted for orientation and some shading, output per installed STC kW is about the same for all systems, including mine. My own system's output is about 1,780 or so kWh/yr. per STC kW.

Check PVOutput for systems near you for reasonably unbiased estimates of systems' outputs. My S.P. output is about the same as other similarly oriented nearby systems., sometimes less.

As for warranty claims, my experience is that panels tend not to fail. There are about 1,400 -1,600 separate panels in my HOA of all stripes/mfg. Over the last 9 or so yrs. I've been keeping track, I think there has been 1 panel failure and that was a fluke that happened on/around startup and a couple others due to wiring screw-ups. There was one golf ball strike.

Sunpower's good stuff, but so is a Mercedes. Solar panels are now a commodity. A Ford is as good a grocery hauler as a Mercedes in terms of fit for purpose. LG or most any quality panel is as fit for purpose as S.P. LG or the others just doesn't come with bragging rights or snob appeal.

Pay your money. Take your choice.

[Sunking]

Thanks everyone... Not much love for SunPower on this forum apparently...

Not if you understand most of the negative comments come from the pros which ought to tell you something valuable. Those that recommend SP are customers to embarrased to admit they made a mistake, and installation contractors who install the panels. Small crowd.

LG and SP are good panels. No one is saying otherwise. What we are saying is they are not worth the price they are asking because you can buy = or better panels for significantly less than both LG and SP.

As a consumer making such an investment, I want to find a company that will be around 20 years from now after the Solar Bubble bust. I would not want to use a company who have a very limited products line restricted to Solar Panels like SP. I want a company where solar is just a side show and solar makes up a very small percentage of their product line. Names I know and trust that have been around a long time and will be around tomorrow to honor their product and warranty. Names like Panasonic Sanyo, GE, Kyocera, and even LG. Companies that only make panels will go bankrupt when the bubble burst never to be seen again Many have already gone bust.

[Ian S]

To add yet another angle, what do you guys think of Panasonic 330W panels? They seem to have slightly better specs and better product warranty (15 yrs vs 10 yrs) than the LG panels but offered at similar price.

Don't be put off SunPower. While the higher efficiency spec is usually not any advantage for most rooftops, the better degradation performance, IMHO, narrows the price gap significantly. Especially if you consider that the lifetime of the panels is far greater than 25 years and that degradation advantage is apt to continue well beyond the 25 year mark. The warranty is nice too but maybe just icing on the cake.

[Mike90250]

Thanks everyone... Not much love for SunPower on this forum apparently.....

It's because they sell moondust, when most folks are just fine with plain dust, IF you have limited space, and IF you need every last bit of power, then I would consider them.
And the other option is to add one or two plain jane panels, and have the same overall harvest or more....

Micro inverters have their scaleability issues, along with a problem they output power at 240V instead of 450-550V and require larger wire gauge and are more prone to tripping off-line from high AV voltage.
To add just one more panel & inverter, requires a new permit and Grid agreement,

[J.P.M.]

On the worth of the POSSIBLE (but effectively impossible to verify) extra (or deficient for that matter) S.P. output over any future period: The accurate way to do it is compare the net present value (NPV) of any possible or expected output of the S.P. system vs. the possible or expected future output of the LG, or any other system. If, any expected additional future savings have a NPV => than the extra S.P. system cost, then the S.P. system is the better choice. Or, a second way to do it: Take the savings by buying the LG system and look around for some other semi liquid investment that will, when left untouched for the same time period, have some probability of producing the same future value as the future value of the possible future additional output of the S.P.system.

Most folks eyes glaze over when such things dealing with NPV or time value of money analysis is involved, which is pretty much what the S.P. folks bet on to sell the premium for their product. But, similar to the value of compounding you may have heard about, things change more than simple +,-,*,/ when time enters the equations.

Usually, with a set of realistic assumptions on such things as time frames, possible (?? - crap shoot - both ways, up and down) electric rate increases, and alternate financial instrument investment rates, and in the end, no more than FWIW, I figure if a S.P. system can be installed for no more than 5 % or so more than a competing system, it's a wash. Any more than that, S.P. is not justified from a cost standpoint with a fair consideration for the ideas, as a practical matter, and based on some measurement and observation, output will be essentially equal for most any quality system for as long as most folks will own it, panel reliability will be about the same, one mfg. to the next and resale value (if any) will be about equal, as will maintenance costs.

But, opinions vary. Some are more informed is all. Knowledge is power.