An article by: Keith Hertz of Haleakala Solar
There is no denying that 1000W = 1kW = 1000W
The same holds true for a typical system size of 6200W = 6200W. So why choose one panel over the other? Haleakala Solar has installed panels from over 20 different panel manufacturers over the last 37 years. With over 12,000 installs you could say we have some experience (more so than any other Hawaiian solar company).
A simple web search of “Top PV Panel Manufacturers” will result in many Top 10 lists. All are relatively different. Some of these lists have repeat offenders but for the most part if you have your eye on a specific panel and you look far enough, chances are you will eventually find it in a Top 10 list somewhere. Once you do, you will have the piece of mind knowing you have selected the right panel… right?
After perusing PV manufacturer site after PV manufacturer site, it becomes apparent that almost every panel manufacturer out there is the #1 panel manufacturer. So what are you to do? Who do you trust? Are more expensive panels better?
If you have limited space on your roof, consider a panel with higher wattage density. These panels produce more watts in a smaller footprint. You may think this is the way to go with every situation however if cost is an issue, keep in mind higher density panels come with a higher price tag.
Remember, a watt is a watt, so if you need 7500w and have enough space, go for a standard density panel of 250W and use (30) panels. If space is not available consider the same 7500W system using (25) 300W panels. Both systems given the same architecture will produce 7500W. The last scenario might save you an additional 90sqft of roof space but usually cost you a little more because you will be getting the same 7500W but in a smaller footprint.
Panel Manufacturers History Matters
Sure, everyone seems to have a 25 year warranty these days. But what if the manufacturer isn’t around in 10 years? It’s important to choose a panel whose company will be around to service the warranty period. Not all manufacturers have a stellar financial forecast so do some checking and a little predicting.
Some manufacturers have even gone to the extent of offering 3rd Party Insurance good for 25 years just in case they go out business. This insurance gives their customers the peace of mind knowing they will be covered in the unlikely event their panels fail and they are no longer in business. I like these companies.
I subscribe to Homepower Magazine. Every two years they come out with a very comprehensive PV Module Specification spreadsheet. The latest list to come out was in 2012 and it has 53 panel manufacturers with 833 different panels. The list is complete with Model Numbers, Cell Types, STC and PTC ratings, Power Tolerance, Module efficiency, physical size, weight, etc… you get the point. It’s comprehensive.
My background as an Engineer pulls me into these details like a tractor beam. After reviewing the list for over an hour it appears very likely most of these panels would perform very similarly given they were all the same rated wattage. Say I took panels from five different manufacturers with the same rating and placed them on my roof. Would I be able to see a discernable difference in the output wattage in a blind test. The answer is NO. We’ve tried it. We have had eight different panel manufacturers on the same roof plane with the same size micro inverter for over two years. The LG, Sanyo, Samsung, Mitsubishi, Hyaundi, Sharp, SolarWorld and Canadian Solar all look the same when the numbers come in.
If the numbers look the same then how do we as a contractor decide which panel manufacturer to go with? It’s easy. Look at the warranty, salt mist rating and the price. You wouldn’t by a new $30,000 car without a good warranty and service plan so why buy a $30,000 solar system without a good warranty and service plan.
The largest contributing factor to the system efficiency is not the panels. It is the inverter. This is where the bottleneck occurs.
System Design Matters
Over the past 37 years we have come to realize the system design plays the most important roll in performance. By design we mean panel layout and inverter selection or architecture.
You can purchase the most expensive, most efficient panel on the planet but if the system architecture doesn’t share the same efficiencies then you’ve just wasted a whole lot of money.
There are two main system architectures (we have installed thousands of each) the string inverter verses the micro inverter. Once again a quick web search will show you that each technology is superior to the other. We install either depending on the circumstance. Here is a little Pro-Con list we’ve put together.
During the past several years we have moved further away from the string inverter architecture and on to the newer micro-inverter technology. This move is mainly due to system reliability and performance. We run a full service department and warrant our systems, which means we are liable if these systems are under performing.
Since the switch to micro inverters (Enphase), troubleshooting by our Service Department has become very easy and we have fewer and fewer production complaints from customers.
In the past if a customer lost a string inverter, we would receive a call as soon as they realized the sting inverter had failed because that meant the entire system failed. With micro inverters it’s usually Haleakala Solar Service Department informing the customer they need an inverter serviced because the customer didn’t notice the loss in production… at least not an entire catastrophic failure.
We have found upfront costs for the micro inverter architectures to be 5 to 10% more than traditional string inverter architectures. However, the added monitoring capabilities and long term system production have always surpassed the string architecture efficiencies. This then decreases the payback time and increases the return on investment. In recent years the costs associated with micro inverters have come down so this price discrepancy is now becoming smaller and smaller. So… in a nutshell, you either pay a little more upfront for Micro Inverters or get less efficiency in the long term and limited troubleshooting with string inverters.
Each customer is different. Each situation has design criteria that must be met. Very rarely is there a case where one size fits all in construction. My advice to investing in a good solar system is:
- Consider the panel placement and determine if higher density panels are required. If not, go with standard panels (1 high density panel watt = 1 standard density panel watt).
- Consider a panel manufacturer that will live up to its warranty (some have salt water exclusion clauses you need to be aware of here in Hawaii).
- Strongly consider the investment in Micro Inverters given their warranties, waterproof enclosures, system efficiencies and monitoring capabilities.
- Choose a solar contractor with a track record… a good track record. According to Forbes magazine 80% of small businesses fail within the first 18 months. The trend is your friend and we’ve already witnessed this struggle with PV Contractors in the Hawaiian Islands (mostly due to utility grid saturation). Your system warranties are only as good as the contractor who installs your system.
In the end, all solar power is good. It’s a never-ending free resource. I think Thomas Edison put it best in 1931. We are like tenant farmers chopping down the fence around our house for fuel when we should be using Nature’s inexhaustible sources of energy — sun, wind and tide. … I’d put my money on the sun and solar energy. What a source of power! I hope we don’t have to wait until oil and coal run out before we tackle that.
Have a Great Sunny Day,