There are a bewildering array of solar panel brands out there. How do you sort the wheat from the solar chaff and be sure you are getting the best solar panels for your roof?
My advice is go thru the spec sheet for each panel and judge them on the following criteria.
If you haven’t got a spec sheet, then get another quote!
If the spec sheet combined with the quote doesn’t have the answers, call up the solar supplier and ask. If they don’t know the answers, that’s a bad sign.
The Top 10 Criteria
It seems that all panels claim to have a minimum 25 year Power Output Warranty. I’ve covered the common myths about solar panel warranties here. But the main criteria is to check that the Warranty is backed by an Australian Entity that has to comply with Australian Consumer Protection Laws, and that it is an “on site replacement” warranty. You really don’t want to be removing the panel from your roof and going down the post office to send it back to China! Plus the last time I checked, Chinese consumer protection laws weren’t that hot. (Note: There are some excellent solar panels, made in China, these days and also some shocking ones – the best way to know if the supplier believes in their quality is to see what responsibility they take for the warranty they offer on them)
Typical prices for solar power systems of different kW sizes are shown here. If the cost of your quotes solar system is substantially less, then make sure you are getting a bargain, not a liability by reading this post about the perils of cheap solar panels.
If the price is much more expensive than those show, then either you have a particularly difficult install, or you are paying too much. Get multiple quotes to check which is the case.
Do a quick Google of the manufacturer – What’s their website like? Is there a “warranty” section? Is there an Australian office? How long have they been around? Has anyone had any bad experiences with them on the forums?
4. Panel Type
Is it a mono crystalline, multi crystalline or thin film solar panel, or some wacky new technology? The types of solar panels and their pros and cons are discussed here. Make sure you are happy with the technology that you choose.
5. Solar Panel Efficiency
Unless you have a huge roof, you probably want an efficiency of at least 12%. Otherwise if you ever want to upgrade in the future, you’ll probably struggle to find any roof space left over. However don’t fall into the trap of believing that efficiency is the be all and end all of solar panel quality. You can get great quality panels at the lower end of the efficiency scale. There’s an in depth discussion on solar panel efficiency, when it matters and when it doesn’t here.
6. Power Tolerance
This is the amount that the actual power output of your solar panel can vary from the output specified by the supplier. For example a 165W module with a tolerance of +/- 5% could actually produce from 156.75W up to 173.25W.
So be aware of this number, as it will directly affect the amount of power you can get.
The best solar panels have a “positive only” power tolerance, which means you are guaranteed to get at least the specified output from the panel and usually more. For example: a 200W solar panel with a tolerance of +5%/-0% will produce a minimum of 200W and a maximum of 210W.
7. Framing Quality
The aluminum frame which goes around the solar panel is a good indicator of the overall quality of the solar panel’s manufacture.
Look at the corners. Are they tidy joins? Are they anodized after the cut, or before. Anodizing after the cut is more time consuming, but means that the 45 degree edge is anodized too, helping protect from corrosion. Are the panels glued (bad), screwed or welded at the corners.
If looks are important to you – then you may want to look for a black anodized frame – they look damn sexy when mounted in a solar array on a roof (I can’t believe I just wrote that what a solar geek I am!)
8. The Backsheet.
All solar panels have a plastic backsheet glued on the the back of the panel to protect the solar cells. A flimsy backsheet with any air bubbles or signs of coming unstuck is a sign of a crappy panel.
9. Bypass Diodes
If your panel is mono or multi crystalline then these are a must. They are diodes that cost a few cents each and are put across neighboring of cells inside the solar panel. If you don’t have bypass diodes then a small shadow on a tiny part of your solar panel can stop the entire panel from making electricity.
10. Temperature coefficient.
This is especially important in sunny Australia!
The temperature coefficient is a number that describes how well the panel handles hot temperatures – where hot is defined as greater that 25 degrees Celsius.
The units of this number are “% per °C”
The lower this number, the better.
The higher this number, the more your power will degrade on hot days, when the sun is at full force! And you thought hat the more sun you had on your roof the more power you would get. Not if this number is too high…
A high temperature coefficient is a sign of a crappy panel. A reasonable number is about 0.5%. The best solar panels get this down to 0.3% and that is the sign of an excellent panel. Over 0.7% is a warning sign.