Did I Get Ripped Off?

[sunshine_eggo]

This is why I expected them to perform better. SunPower claims 20% effiency. Talesun only claims 16%. Yet they perform the same.

Oh, and if you think that picture is seductive, you are playing for the wrong team buddy. So keep your fantasies to yourself.

No fantasies here. I just thought it was funny.

View attachment 81285

Sadly, you've been misled by marketing.

They're just saying they'll get more for the same surface area ("45% more energy from the same space"), and they degrade slower.

You're confused about efficiency. These are 435W rated panels. Their efficiency manifests as their size. They are smaller than a 16% efficient 435W panel, but BOTH 16% and 20% efficient panels will produce 10% of their rating if they're getting 10% standard insolation.

Explained in numbers:

435W panel #1:
16% efficient
2.72m^2 surface area
43.5W produced when solar insolation is 10% of standard.

435W panel #2:
20% efficient
2.18m^2 surface area (about 20% smaller)
43.5W produced when solar insolation is 10% of standard.

Again, $0.38/Watt is great. Take the win.

If nothing else, they make a hard claim that they have a slower degradation rate than other panels. There's your $0.18/Watt premium. You'll be getting more energy over the years.

 

[ed6269]

No fantasies here. I just thought it was funny.




Sadly, you've been misled by marketing.

They're just saying they'll get more for the same surface area ("45% more energy from the same space"), and they degrade slower.

You're confused about efficiency. These are 435W rated panels. Their efficiency manifests as their size. They are smaller than a 16% efficient 435W panel, but BOTH 16% and 20% efficient panels will produce 10% of their rating if they're getting 10% standard insolation.

Explained in numbers:

435W panel #1:
16% efficient
2.72m^2 surface area
43.5W produced when solar insolation is 10% of standard.

435W panel #2:
20% efficient
2.18m^2 surface area (about 20% smaller)
43.5W produced when solar insolation is 10% of standard.

Again, $0.38/Watt is great. Take the win.

If nothing else, they make a hard claim that they have a slower degradation rate than other panels. There's your $0.18/Watt premium. You'll be getting more energy over the years.

exactly , this is what i was thinking while reading all the comments.

 

[Ralo]

You're confused about efficiency.

I figured that out by myself by reviewing my spreadsheet. Covering my roof with the Sunpower panels produce 13,050kw, using the cheaper panels only produces 10,000kw. So looks like the Sunpower panels are much more effiecient for the space used. To bad you didn't lead with that info, that would have been much more help. I see you have a reputation for insulting people. I guess that helps your eggo.

 

[iamrich]

I purchased 30 used Sunpower E-Series Commercial Solar Panels E20-435-COM from ebay and they are advertisted to be working at 98% of out of the box capacity. However, when I tested several of them today in clear, direct sunlight, I'm only getting 80-85% of the rated 435w output. Did I get ripped off?

This time of year, I would be very surprised if you got 98% out of a brand-new panel, never mind used. You could have gotten 250w panels for half that price, but if you are working with limited real estate, that limits your options. I have been looking at those same panels for a while now (I assume the outfit out of Florida), but the cost is still a little high for me. Still panels less than 3 years old should serve you well for decades to come.

 

[sunshine_eggo]

I figured that out by myself by reviewing my spreadsheet. Covering my roof with the Sunpower panels produce 13,050kw, using the cheaper panels only produces 10,000kw. So looks like the Sunpower panels are much more effiecient for the space used. To bad you didn't lead with that info, that would have been much more help.

It took several posts to figure out what your motivation was.

I see you have a reputation for insulting people.

Really? Where?

I guess that helps your eggo.

Please... Please... Please... tell me that's a play on words and not a typo, because it's GENIUS!

 

[RCinFLA]

'Low light' panels are built with PV cells selected for low shunt leakage current (high parallel shunt resistance). A usable PV cell can have an effective shunt resistance from 5,000 ohms (exceptionally good) to less than 1 ohms (very poor).

PV Cell shunt leakage is one criterion tested and sorted for by panel manufacturers. Spot defects in the PV wafer are the cause of the shunt leakage current.

This does not preclude a PV cell from developing a worse shunt defect after some usage.

 

[iamrich]

Please... Please... Please... tell me that's a play on words and not a typo, because it's GENIUS!

You do have a reputation for insulting breakfast...

 

[Ralo]

This time of year, I would be very surprised if you got 98% out of a brand-new panel, never mind used. You could have gotten 250w panels for half that price, but if you are working with limited real estate, that limits your options. I have been looking at those same panels for a while now (I assume the outfit out of Florida), but the cost is still a little high for me. Still panels less than 3 years old should serve you well for decades to come.

I had the cheaper panels in my spreadsheet, but I could get 3000 more kilowatts on my roof with the Sunpower panels. An I'd hope for better low light performance. Now I'll just have keep my 20 265w panels in a group mount array. Hopefully that will be enough to keep 50kw of batteries charged up.

 

[iamrich]

I had the cheaper panels in my spreadsheet, but I could get 3000 more kilowatts on my roof with the Sunpower panels. An I'd hope for better low light performance. Now I'll just have keep my 20 265w panels in a group mount array. Hopefully that will be enough to keep 50kw of batteries charged up.

What is your daily usage? In theory, your array just has to outproduce your usage before the battery hits bottom.

 

[Ralo]

What is your daily usage? In theory, your array just has to outproduce your usage before the battery hits bottom.

My daily useage is not what it would be if I had more juice. I run through 5 gallons of gas and 40 pounds of propane every two days in the winter just to stay warm and keep the lights on. And my batteries haven't had a full charge in over a month. Not enough time in the day and I'm using them again at night.

I need all the solar I can get. I'd rather have too much than too little. Panels are bought. Going up the weekend. Sunny Boys on the way.

 

[sunshine_eggo]

My daily useage is not what it would be if I had more juice. I run through 5 gallons of gas and 40 pounds of propane every two days in the winter just to stay warm and keep the lights on. And my batteries haven't had a full charge in over a month. Not enough time in the day and I'm using them again at night.

I need all the solar I can get. I'd rather have too much than too little. Panels are bought. Going up the weekend. Sunny Boys on the way.

Fun with math, translating BTU to kWh to equate to shifting fuel consumption to solar:

1 gallon of gas = 116,090 BTU
1 pound of propane = 21,600 BTU

21,600BTU = 6.36kWh
116,090 BTU = 34.023kWh

5 gallons of gas is 170kWh
40 lb of propane is 254kWh
Two day total = 424kWh

Fuel consumption per day: 212kWh

If the bulk of your propane consumption is your RV furnace, those are maybe 60% efficient. Since electric heat is close to 100% efficient, let's apply that to the total:

.6 * 212kWh = 127kWh

You're going to be hard pressed to offset 127kWh of fuel consumption with solar. That's more than my home in phoenix uses running the A/C when it's 120°F outside.

5th wheels have shit insulation. Have you considered skirting with foamboards? You'll probably save a fair amount.

EDIT: incorrectly used energy for gal of propane vs. lb. Revised to use lb.