Solar panels – High vs. regular efficiency. What’s best?

From time to time some customers ask about high efficiency solar panels (aka. Sun power). Some  say, “I don’t want Chinese made solar panels.” This blog post will analyze the issue and provide you a framework to make a smart decision.

If you are not blinded by the marketing blitz of some solar panel manufacturers, you will realize that for the most part there are very subtle differences among solar panels. They are like a commodity. Here is a framework to decide what solar panels are good enough for your project:

1. It’s easy to compare  the output of solar panels side by side.

The purpose of a solar panel is to convert sunlight and generate electricity. Many years ago the solar industry settled on how to rate the output of each solar panel with the same bar. This is called the Standard Test Conditions or STC. Each solar panel is exposed to artificial sunlight with an intensity of 1000 watts per square meter at a temperature of 25°C (77 °F) with an atmospheric density of 1.5. This represents the position of the sun at noon in the spring and autumn equinoxes for the continental United States with the surface of the cell aimed directly at the sun. What does it mean? If you have 2 modules from different manufacturers but with the same STC rating (example 310 watts) you would expect to have very similar electricity generation.


2. What about high efficient solar panels? is high efficiency important?

The solar panel efficiency is the ratio of the electrical output of all  the solar cells in the panel to the sunlight received (incident energy). In other words, how good is a solar panel to convert sunlight to electricity. But high efficiency doesn’t mean better, it just means high efficiency solar panels use less space on your roof. But remember all panel output is measured equally, under STC. The STC output rating does not change if the panel is more or less efficient. A 310 watt module that is high efficiency is no better than a 310 watt module that is not high efficiency. So efficiency isn’t usually a critical concern unless you have an unusually small space for your solar panels. The most efficient solar panels cost a little more, so they are a less common choice.

If you are still not convinced, think about this, if high efficiency solar panels were the best possible option, wouldn’t you think the designers of large utility scale projects would use them? Afterall, the sharpest financing minds have evaluated these projects and products used to build them. Read below.

3. The most important CRITERIA to watch… “Bankability.”

Make sure your solar system has solar panels and inverters with warranties from manufacturers that will be around to honor the warranties. In large utility scale projects, this is referred as “bankable” manufacturers. Investors and lenders conduct extensive due diligence into these manufacturers. These projects are financed by the smartest financiers like Wells Fargo, Bank of America, US Bank, Morgan Stanley, JP Morgan, etc. Nothing can doom a solar project faster than selecting non bankable equipment. The same solar panels that are use to install on the rooftop of a commercial building are the same used to build utility scale solar power plants.

Wiki-Solar has done the work for you by compiling a ranking of the most popular solar panel manufacturers for utility scale solar projects as of the end of 2014. So, make sure the solar panel for your commercial solar system is on the list below.

Leading suppliers of modules for utility-scale solar power plants

  1. First Solar 4.6 GW
  2. Yingli Solar 1.2 GW
  3. Hanwha / QCELLS, 1.1 GW
  4. Suntech 1.0 GW
  5. Canadian Solar 0.9 GW
  6. SunPower, 0.8 GW
  7. Trina, 0.8 GW
  8. Jinko, 0.8 GW
  9. JA Solar, 0.5 GW
  10. Kyocera, 0.4

Note: 1 GW = 1,000 MW = 1,000,000 kWp (STC)


  1. SMA, 1.7 GW
  2. Schneider Electric, 0.7 GW
  3. SunGrow, 0.6 GW
  4. Santerno, 0.4 GW
  5. ABB, 0.4 GW

4. The real efficiency you need to care about… the economic efficiency.

The ratio of dollars to electricity generation. How much does it cost to generate 1 kWh? (Kilowatt Hour) The key here is to compare apples to apples. To do so, you can use the U.S. Department of Energy tool to produce an energy forecast, or use a more sophisticated tool such as PVSyst, Helioscope, or others. But beware of forecasts not generated by a third party (aka generated by solar panel manufacturers). So, to calculate this ratio simply divide the cost to install your solar system by the forecast kWh generation for the first 12 months.

5. DO I get a Flash test report for the specific solar panels to be installed on my project?

A solar flash test measures the output performance of a solar panel at industry standard conditions. At K12 Solar we have the solar panel manufacturer send us the flash test results for every single solar panel we install.  We share this report with any customer who is interested. This is a way to ensure our customers are getting what they pay for by verifying all panels are within the tolerance. A solar module tolerance is the specified range within which a solar panel will either over-perform or under-perform its rated power at STC. All modules we install are positive tolerance. Power tolerance can vary greatly from solar panel to solar panel, so make sure the panels being installed for your project are all positive tolerance.

6. Where are the solar panels manufactured?

Some customers do not want to have Chinese solar panels. But keep this in mind, 8 out of the 10 most used solar panels for utility scale projects are from Asian companies. Remember, these are “bankable” manufacturers and have been vetted by the sharpest investors. Also to consider, because a company is headquartered in the U.S., does not mean the products are manufactured in the U.S. for example SunPower.

7. Who’s behind the solar panel manufacturer?

Customers are sometimes fixed on “not Chinese” and they usually forget to ask who owns or is behind the solar manufacturer. For example, it is not highly advertised that 66% of SunPower is owned by an French Oil company, Total. For some this can be negative, but not for others.


I hope these comparison frameworks will help you decide if the solar panel your solar installer is proposing is good enough for your project.


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