Solar Panel Comparison Tips

By Finn Peacock, Chartered Electrical Engineer, Fact Checked By Ronald Brakels

How do you compare solar panels? I’m glad you asked! Here at SolarQuotes we’ve put together a handy comparison tool:

If you want a higher level view on the differences between brands, in the video below  I go through 3 simple things you can look out for when comparing products.

If you’re in a hurry, just watch this and you’ll massively reduce your risk of buying a crappy product that won’t last. After the video I go into even more detail if you are feeling like getting knee deep in solar panel comparisons!

There is a bewildering array of solar panels on the Australian market. At the last count, there were over 4,300 models from nearly 100 manufacturers approved for use in Australia!

If you look at a solar panel specification sheet (aka datasheet), it can often look like a physics textbook, full of numbers and strange symbols. For those of us without a degree in rocket-science, how do we make an informed solar panel comparison?

Well, I reckon there are 5 things you need to look at when choosing solar panels for your home to maximise the chances you are getting good quality products.

1) ‘Tier 1’ solar panels – does it matter?

‘Tier 1’ refers to a ranking given to solar panel manufacturers by ‘Bloomberg New Energy Finance’. They publish a quarterly list and charge thousands of dollars to access it.  Tier 1 is not a direct measure of quality or performance. It measures how ‘bankable’ the solar panel manufacturer is.  In other words – how likely are they to stay in business. Solar farm builders use it to reduce the risk of panel manufacturers going bust. If you are building a large-scale solar power station, your investors won’t go near you unless you use solar panels from a Tier 1 company. Getting a panel from a Tier 1 manufacturer is pretty low risk because the big manufacturers used in solar farms are almost all on top of quality control.

Just be aware of less-than-honest salespeople who will insist their panels from WaWaSuperHappySolar are Tier 1!

Tier 1 manufacturers include: Trina, Canadian Solar, Longi, JA Solar, and REC to name a few.

Non-Tier-1 manufacturers are the smaller players that produce panels. You can get some good panels from them, but unless you know the solar manufacturing landscape, it is a lot riskier – because 80% of the lower tier panels are junk. Also, the smaller companies are less likely to be around in the future. For those reasons, I always recommend the non-solar expert to stick to Tier 1 panels – unless the manufacturer has a good record for reliability and customer service in Australia.  For example, Australian made Tindo Solar panels are not Tier 1, but I’m more than happy to have them on my roof because I know they’re well made.

You can read more about the tier ranking system for solar panels here.

2) Comparing Warranties

Be aware that all solar panels come with two warranties – a performance warranty and the product warranty (also known as the manufacturer’s warranty). 

Performance Warranties:  Most performance warranties are for 25 or 30 years and promise a panel’s performance won’t deteriorate by more than a given amount.  Some performance warranties are better than others, as the following graphs show:

Two solar panel performance warranty graphs.

The first allows up to 2% capacity loss in the first year and then up to 0.45% of its original capacity each year after that.  This means, after 30 years, it will have at least 84.95% of its original capacity.  (The grey area on the graph is meant to show how much better it is than an older 25 year warranty.)

The second allows just 1% loss in the first year and then 0.4% loss each year after that.  This gives a minimum of 87.4% of original capacity after 30 years.

The second performance warranty is clearly better.  If both panels degraded by the maximum permitted amount, the second panel would, all else equal, produce around 1.5% more energy over its first 20 years.  However, because panels normally deteriorate by less than the maximum allowed, the actual difference is only likely to be around 1%.

Product Warranties:  The second type of warranty panels have is the product or manufacturer’s warranty.  This covers panels against faults in materials and construction.  They’re easy to compare because longer is better.  They are also normally considered much more important than the performance warranty because, in practice, it’s very difficult to accurately measure panel deterioration.

Don’t buy a panel with a manufacturer’s warranty of less than 10 years.  These days most good quality panels have at least 12 or 15 year product warranties.  It’s also now easy to get low cost but well made panels with 25 year product warranties.  Some manufacturers now offer 30 years and, if you don’t mind paying a premium, the longest product warranty around is 40 years from SunPower.

4) Power Tolerance

Power tolerance refers to how close a solar panel will be to the specified wattage in real-world conditions. For example, if it is a 440-watt panel and the power tolerance is +/-3%, your actual wattage could be from 427 watts up to 453 watts.

These days many quality panels have a “positive only” power tolerance, with +0-3% being common. That means a 440W module will never be less than 440 watts and could be up to 453 watts.  A positive only power tolerance is better than a plus or minus because always getting at least what you paid for is better than a 50% chance of getting less.  But it normally makes little difference to total output over a panel’s life.  In practice, the extra amount from from positive tolerance usually averages to under 1%.  Because of the small difference it makes, power tolerance is probably best used as a tie breaker when making a choice between very similar panels.   

5) Efficiency Comparison

When comparing panels, efficiency is not as important as most people think.  As long as the module efficiency is over 20%, it should be fine. More efficient panels don’t produce more electricity, they just take up less room on your roof.  Unless roof space is critical, don’t stress about efficiency.

If roof space is critical, a 23% efficient panel can produce 15% more energy per square metre than a 20% efficient panel.  As this difference is worth chasing, higher efficiency panels are definitely worthwhile, given it’s no longer necessary to pay premium prices for them.  

5) Compare Temperature Coefficient

Solar panels love sunlight, but they hate heat. Their power drops as they get hotter. The temperature coefficient measures how much their power output reduces for every degree rise in temperature above 25°C – and that’s panel temperature, not ambient temperature. The temperature coefficient generally ranges from under -0.3% per °C (good) to -0.4% per °C (not as good). In the latter case, if the panel temperature goes up 20°C, the power will drop 0.4 x 20 = 8%.

While this loss of power isn’t good, it’s not a major problem because panels only get really hot when there’s plenty of direct sunshine and so plenty of solar generation.  A low temperature coefficent is still useful, but only to a modest extent.

That’s All

By keeping the above 5 points in mind, you can compare solar panels with a good degree of confidence and sift out the spin.

>> Next: Is Your Roof Angle Suitable For Solar Panels? >>

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