Being in this industry I have to be careful what I say about particular brands. But I can probably make the following points:
- The cheaper end of the market has its place. I have clients who have five year leases (commercial lessees) and just want the cheap stuff because it's a two year payback and they don't care if it doesn't last anymore than five years. Doubling their capital in five years is fine by them. That's fair enough but they still want the cheap stuff from a reputable long term retailer and distributor so they have someone to chase for the warranty issues. This strategy makes sense for them - they can take comfort in the warranties from the distributor and the retailer at least. That can work for some panels but getting real long term support on cheap inverters is less certain.
- Apart from that particular situation, I would never advise a client to go to that end of the market. This industry has been around for a long time now and there is regular churn of suppliers (distributors and retailers) going broke in that space. The long term successful solar companies (with one or two notable exceptions who are currently facing big challenges in any case) are the ones selling the quality gear.
I continue to be amazed that people who wouldn't dream of buying a Great Wall or Chery will go for the equivalent in the solar market, with roughly the same price differential in play.
If you want technical reasons, silicon ain't silicon - it comes down to:
- Obvious efficiency and degradation differences
- Hand laid panels and frames with poor adhesives / epoxies made in poor conditions vs automated assembly lines with quality materials in clean room semiconductor conditions. The difference is obvious upon close inspection and comparison.
- There is a world of difference in just the panel connectors and their safety. There is a PV World article you can download here on it:
http://www.multi-contact.com/products/original.php
Plenty of others around the traps too - quick google and you will see them. Same applies to rooftop DC isolators.
- This video is also worth a look on inverters:
http://www.energymatters.com.au/renewable-news/em3152/
- Many inverters are able to pass current testing requirements but still not actually be compliant with the underlying technical rules - the new AS4777 will hopefully help weed this out in future but currently it's a big problem and has long been an issue with network companies being "unhelpful" in solar connections because they can't differentiate by brand but in truth they are much more comfortable with the algorithms used at the top end of the market rather than elsewhere...
This issue has been a terrible one for this industry - we just haven't done a good job (as an industry) of educating the public on what constitutes good quality panels and inverters and why they are worth paying for. If someone really wants to know they have to spend hours and hours trawling Whirlpool threads for the info. The car industry is a good model for us about how to do it properly. Very few people will want the Porsche level ($2/W) but I reckon a lot more people would go for the Toyota ($1.5/W) if they knew the real differences over the Chery ($1/W). Unfortunately the people selling the Chery will deny their being any differences. While this is somewhat debatable on panels, it really isn't on inverters. At the end of the day, this is just the same as any other semiconductor device in the market except when you buy a bottom of the range TV you don't expect it to last twenty years operating outside for 8 hours a day, 7 days per week!
Keep in mind also that this isn't a China thing despite the brands I've used above for comparison - some great stuff comes out of China in solar. But the reality is that, for equivalent quality, China no longer enjoys any real price advantage. It's just that a lot more Chinese manufacturers are prepared to bring to market poor quality panels and inverters than is the case in other countries. You pay for that in lower energy production (which only a tiny % of the market ever properly checks) and much higher failure rates, particularly on inverters. And discoloured panels aren't a good look, regardless of whether they're still producing. You pay for what you get, just like everywhere else.
In my personal view, if this is a >5 year investment, the marginal cost of stumping up for the Toyota level is well worthwhile.