Is Sunpower price difference worth it? -- thoughts, posting as new topic

[sunnyguy]

Really, if given a reasonable estimate for sunpower, which for a 3kW-5kW system is around $4.40-4.60 per watt and $4.10-$4.30/watt for 6kW-9kW and $3.90-$4.10 for 10kW+ systems, the price difference IS worth it. You will get 75% more energy over the lifetime of the panels. 8% more per rated watt, the degradation rate for Sunpower is actually only 33% of or 3 times better than the LG panels. You'll use, in your case, 1 less panel. I'd take a hard look at the extended production guarantee on the LG proposal before you go forward with it. If you need any more info I'd be glad to help.

Ooooh. Ahhhhh. What other dancing monkey tricks do you have for us?

[solar pete]

Really, if given a reasonable estimate for sunpower, which for a 3kW-5kW system is around $4.40-4.60 per watt and $4.10-$4.30/watt for 6kW-9kW and $3.90-$4.10 for 10kW+ systems, the price difference IS worth it. You will get 75% more energy over the lifetime of the panels. 8% more per rated watt, the degradation rate for Sunpower is actually only 33% of or 3 times better than the LG panels. You'll use, in your case, 1 less panel. I'd take a hard look at the extended production guarantee on the LG proposal before you go forward with it. If you need any more info I'd be glad to help.

Hi Advice4SoCal it is not cool for newbies to come here seeking free advertising or self promotion, and trying to justify Sunpowers sales hype BS is not going to go down to well either, cheers.

Really, if given a reasonable estimate for sunpower, which for a 3kW-5kW system is around $4.40-4.60 per watt and $4.10-$4.30/watt for 6kW-9kW and $3.90-$4.10 for 10kW+ systems, the price difference IS worth it. You will get 75% more energy over the lifetime of the panels. 8% more per rated watt, the degradation rate for Sunpower is actually only 33% of or 3 times better than the LG panels. You'll use, in your case, 1 less panel. I'd take a hard look at the extended production guarantee on the LG proposal before you go forward with it. If you need any more info I'd be glad to help.

[KingAntonio]

I had this question when i started doing my research and going by everything i read the short answer is NO. I'm installing RenoSolar in a few days. Good luck

[J.P.M.]

You are correct, it's a marketing tool the really means nothing, but people pay up for it.

Well, some people do. (A few) Others know better.

[Yaryman]

Enough already. The S.P. warranty, like most solar warranties, is a marketing tool. Leave it at that.

You are correct, it's a marketing tool the really means nothing, but people pay up for it.

[sensij]

Suddenly one panel drops to 75%. So I now have 17 panels producing 1.44 kWh and one panel producing at 75% or 1.08 kWh for a grand total of 25.5 kWh.

Your definition of "failure" is much too narrow. How often does a single panel drop 25%? Most of the common failure modes, which are already rare, would drop the panel voltage by at least 33%, which is relatively detectable because it isn't very sensitive to irradiance. Yes, any failure mode that affects *only* current output would be harder to detect, but can you even propose how that could happen? The monitoring on string inverters is sufficient to detect most of the known types of failure, especially with two similar arrays to compare.

[J.P.M.]

Solar Pete, bcroe, and samotlietuvis,

My point still is that without individual panel monitoring, the Sunpower warranty is virtually useless.

You represent the elite of the elite solar panel owners. You aren't the 1%, you are the .1%. ( congratulations )

How many owners can look at the temp and wind speed and determine what their output should be? ( Solar Pete )
How many owners have identical strings and take DC meter readings? ( bcroe )
How many owners check string Voltage and Current over time. ( samotlietuvis )

How would any of you three know which panel had gone bad?

Would you call your installer and say, well my production has dropped from 25.86 kWh to 25.50 kWh, could you come out and check all my Sunpower panels?
What would you say after the laughter on the other end of the phone call ended.

Here's the math on those numbers just using my panels. ( not sunpower )
18 280 watt panels producing 25.86 kWh. That's about my average for the last week on sunny days.
Suddenly one panel drops to 75%. So I now have 17 panels producing 1.44 kWh and one panel producing at 75% or 1.08 kWh for a grand total of 25.5 kWh.

I'm not pimping micro inverters or Solar Edge, just saying without one of those 2 systems its, VERY, VERY, VERY unlikely most people
that own Sunpower systems could or would EVER detect a single panel failure.

I don't think anyone is disagreeing with the idea of the difficulty of monitoring individual panel output. Similarly, most folks who have vehicles powered by multicylinder ICE's will probably have trouble monitoring individual cylinders. More to the point, most don't care. An 8 cylinder Camaro costs less than an 8 cylinder Mercedes roadster. The Mercedes warranty is a bit better. Most owners probably don't monitor each cylinder, but probably notice a performance drop off if the vehicle's performance is important to them.

Same goes for solar array performance. Some folks care. Some not so much. Some, none at all.

Enough already. The S.P. warranty, like most solar warranties, is a marketing tool. Leave it at that.

[cebury]

Here's the math on those numbers just using my panels. ( not sunpower )
18 280 watt panels producing 25.86 kWh. That's about my average for the last week on sunny days.
Suddenly one panel drops to 75%. So I now have 17 panels producing 1.44 kWh and one panel producing at 75% or 1.08 kWh for a grand total of 25.5 kWh.

Is the math even close to accurate for string inverter systems?

[Yaryman]

Solar Pete, bcroe, and samotlietuvis,

My point still is that without individual panel monitoring, the Sunpower warranty is virtually useless.

You represent the elite of the elite solar panel owners. You aren't the 1%, you are the .1%. ( congratulations )

How many owners can look at the temp and wind speed and determine what their output should be? ( Solar Pete )
How many owners have identical strings and take DC meter readings? ( bcroe )
How many owners check string Voltage and Current over time. ( samotlietuvis )

How would any of you three know which panel had gone bad?

Would you call your installer and say, well my production has dropped from 25.86 kWh to 25.50 kWh, could you come out and check all my Sunpower panels?
What would you say after the laughter on the other end of the phone call ended.

Here's the math on those numbers just using my panels. ( not sunpower )
18 280 watt panels producing 25.86 kWh. That's about my average for the last week on sunny days.
Suddenly one panel drops to 75%. So I now have 17 panels producing 1.44 kWh and one panel producing at 75% or 1.08 kWh for a grand total of 25.5 kWh.

I'm not pimping micro inverters or Solar Edge, just saying without one of those 2 systems its, VERY, VERY, VERY unlikely most people
that own Sunpower systems could or would EVER detect a single panel failure.

[solar pete]

So the Forum Administrator of the most popular Solar Forum in the known solar system has a pretty good read on his solar production.
( triple word score for using the word solar three times in one sentence )

Sorry to give you the bad news, but you aren't they typical residential solar panel owner. Not by a long shot.

It doesnt matter, the point is that after looking at my solar system practically everyday and at various times of the day over several years, I have come to be able to predict quite acuratly what my system will be producing , anyone will be able to do that after enough time, well ok a lot of people will be able to work it out. Like many thinks its a personal choice thing, me I hate micro inverters and avoid them like the plague, but I work with people who like them, in the same office, go figure.

[bcroe]

If over time, one of those 17 Sunpower panels dropped to 75% production vs the other
panels, you are claiming you would know?

How? You have no baseline you can compare the output to. How often do you check the sting voltage and current?

How would you know which one went bad? Are you going to call your installer and ask them to check each panel
cause you think production is down 25% on one?

Sure there is a baseline, use another string. Even if a different length, with the same orientation (and no shade)
the outputs will be directly proportional, assuming each has its own MPPT.

If one panel in a string fails, the output of the string will drop. If you study up on panel curves, you will see that a panel
or maybe 1/3 of a panel will be bypassed, causing the rest of the string to ramp up their voltage (to match another
parallel string) and drop current. I have detected 1/3 panel not keeping up in a string of 10. Once the failure is
detected, tracking down the panel is on the same level of difficulty as replacing it.

In addition, you will find that the MPPT voltage of a panel varies little, mostly with temperature. Variation are
not hard to spot. Of course all this is a lot easier with a ground mount; difficult access might justify more elaborate
monitoring. But in the bigger picture, the panels are the thing least likely to fail. All the other stuff can and will fail,
and panel monitoring won't pinpoint the issue. The simplest system able to serve the situation will be the most reliable.

Some people drive a car, some change the oil, that is fine. I rebuild my automatic transmissions. Not everybody
is up to system operational details or hands on with meters and dangerous wiring. So a fancy software monitoring
system can help compensate, but in the end it will rarely be used or needed for fault finding. Production over time
is a simple occasional number off your inverter display, which is more accurate than the individual monitoring since
it also takes into account DC wiring losses. Bruce Roe

[Yaryman]

I would know if I had an issue with my system, after looking at it a lot over several years I pretty much know what to expect, ok I will do a live experiment its 12.37 pm here in SA its 28 dgree;s I ill guess my little array will be pumping out around 1400 watts, now I will run outside to check.....its 1451watts.....I consider that good enough for me

So the Forum Administrator of the most popular Solar Forum in the known solar system has a pretty good read on his solar production.
( triple word score for using the word solar three times in one sentence )

Sorry to give you the bad news, but you aren't they typical residential solar panel owner. Not by a long shot.

[sensij]

If over time, one of those 17 Sunpower panels dropped to 75% production vs the other panels, you are claiming you would know?

How? You have no baseline you can compare the output to. How often do you check the sting voltage and current?

How would you know which one went bad? Are you going to call your installer and ask them to check each panel cause you think production is down 25% on one?

On paper, it seems like it would be easier to identify a panel that has gone bad with a microinverter or SolarEdge system. In practice, if you look over the forum content of the past couple years, it looks like the only failures that have been identified are with the panel level electronics themselves (micros or optimizers). When the tool you are hoping will help find problems is the one creating them, that isn't very good.

I'm not sure what the right answer is... there are tradeoffs to every system currently on the market today. All I can suggest is to get educated about the strengths and weaknesses of each and choose what is likely to be the best fit for you.

[solar pete]

If over time, one of those 17 Sunpower panels dropped to 75% production vs the other panels, you are claiming you would know?

How? You have no baseline you can compare the output to. How often do you check the sting voltage and current?

How would you know which one went bad? Are you going to call your installer and ask them to check each panel cause you think production is down 25% on one?

I would know if I had an issue with my system, after looking at it a lot over several years I pretty much know what to expect, ok I will do a live experiment its 12.37 pm here in SA its 28 dgree;s I ill guess my little array will be pumping out around 1400 watts, now I will run outside to check.....its 1451watts.....I consider that good enough for me