It all depends on what is important to you. Two things that can be important are cost and size.
For applications where space doesn't matter (like putting panels in your back yard or on your roof), you want to make the most power for the least cost. Here is what I've found...
Solar Panels ranked by least cost per unit of power (best first)
Clearly, large panels bought in bulk are more economical. Interestingly, this most economical big panels are also relatively efficient. Unfortunately their large size limits their practical use to stationary applications.
For mobile applications (solar powered cell phone or lawn mower), you want the most power per unit of area. Here is what I found...
Solar Panels ranked by minimum size per unit of power (best first)
|Name||Volts (v)||Current (ma)||Height (in)||Width (in)||Price (US$)||Power (mw)||Area (in^2)||Economy ($/W)||Efficiency (mw/in^2)|
|Special Photo-Voltaics (not soldered, not weatherproof)||0.5||1300.00||2.36||2.76||$ 12.95||650||6.51||$ 19.92||99.85|
|Folding Model||18||1000.00||11.00||17.50||$ 479.95||18000||192.50||$ 26.66||93.51|
|Space Age Solar Panel (1A)||9||1000.00||8.75||12.25||$ 139.00||9000||107.19||$ 15.44||83.97|
|Space Industry Super Cells (not soldered, not weatherproof)||0.5||500.00||1.57||1.97||$ 9.98||250||3.10||$ 39.90||80.65|
|Sharp 200W Solar Panel||28.5||7002.00||64.60||39.10||$ 930.00||199557||2525.86||$ 4.66||79.01|
|SolarPort 4.4||12||366.67||9.30||6.00||$ 139.00||4400||55.80||$ 31.59||78.85|
|PHOTOVOLTAIC SOLAR CELL 8V 50UA (SIOC package)||8||0.50||0.14||0.38||$ 1.63||4||0.05||$ 407.50||75.19|
|Kyocera 40 watt solar panel, KC40T||17.9||2224.00||20.70||25.70||$ 260.00||39810||531.99||$ 6.53||74.83|
|Space Age Solar Panel (500ma)||9||500.00||8.75||7.00||$ 89.00||4500||61.25||$ 19.78||73.47|
|Highest Power-To-Size Ratio Panels||8.5||250.00||3.75||7.75||$ 63.95||2125||29.06||$ 30.09||73.12|
|Northern Industrial Tools Solar Panel — 350 MA||12||350.00||12.00||6.50||$ 79.99||4200||78.00||$ 19.05||53.85|
|SCC3766 - 37 x 66mm Polycrystalline Solar Cell||6.7||30.00||1.46||2.60||$ 11.00||201||3.79||$ 54.73||53.10|
|Encapsulated High Output Solar Cells||6||50.00||3.75||2.00||$ 19.95||300||7.50||$ 66.50||40.00|
|Low Cost–High Output Encapsulated Solar Cells||0.45||400.00||3.00||1.75||$ 5.95||180||5.25||$ 33.06||34.29|
|Northern Industrial Tools High Wattage Solar Panels||12||1250.00||38.00||13.00||$ 79.99||15000||494.00||$ 5.33||30.36|
|PowerFilm MPT6-150||6||100.00||4.50||5.90||$ 23.75||600||26.55||$ 39.58||22.60|
|WeatherPro P7.2-150||7.2||200.00||10.30||6.90||$ 59.89||1440||71.07||$ 41.59||20.26|
|Thin Film Flexible Amorphous Silicon Cells||12||50.00||10.60||3.90||$ 34.95||600||41.34||$ 58.25||14.51|
Interestingly, some efficient panels are also economical. For my application, I picked the "Space Age Solar Panel (1A)" from Edmund Scientifics because it was very efficient and economical and almost exactly the size and power I needed.
Please note that I am basing these lists on the data supplied by the referenced web pages. I have not (yet) tested any of these panels. I have ordered several of the best and will report back when I've had a chance to test them.
Q: Why didn't you include X?
A: If you know about an interesting panel that is commercially available and not included here, send me a link where I can see its specs and actually buy it and I will add it to the list.
Q: It is not fair to mix some raw cells with others that include connection lugs and weather sealing.
A: I agree. I just wanted to get a general feel for what was available, and I was surprised at what I found. The raw cells are not nearly as cheap or efficient as I would have expected compared to some of the fully assembled panels. I've noted which panels/cells are not weatherproof as offered.
Q: I want to install a solar system for my house. Which of these should I pick?
A: You'll want to get very large (typically several feet high) and cheap (typically ~$5 per watt) panels. These are available from a number of great manufactures like Sharp, Kyocera, and Evergreen. Search the web to find the best deal ($ per watt) you can that matches your output requirements (volts and amps needed) keeping in mind that you can combine panels either in series to combine their voltages or in parallel to combine their currents.
Q: Why didn't you make a nice graph?
A: I tried, but gave up getting Excel to do a proper XY Scatter Plot of this data. You are welcome to download my spreadsheet here and give it a try yourself. There is also a Google version here.
If you have any questions or suggestions, you can reach me at...
5/21/07 - Initial upload.
6/1/07 - Added a couple of panels from Northern Equipment.
8/1/07 - Added some really cheap panels from Aten.
8/27/07 - Perfected the embedded Google spreadsheet. Unfortunately I still cannot figure out how to (1) display the spreadsheet sorted on different columns, and (2) create an XY scatter plot of the efficiency/econonmy of the panels where the name of each panel would show up as a label next to its point. If you know how to do this, please let me know!
6/1/09 - Added the Mars Phoenix solar cells to the list thanks to data from Chris Lewicki at JPL. These are pretty amazing cells.