One of the most frequently asked questions by people researching a solar power system for their home or business is the difference between panel and cell efficiency, both which work to determine the energy production and cost saving benefits of a system.

In the solar industry, efficiency refers to the percentage of sunlight energy hitting a cell or panel that is converted into electricity. SunPower’s world-record efficiency Maxeon cells, for example, achieve efficiencies of 22.4%, which means they convert 22.4% of the sunlight that hits them into electricity. Solar technology on the market today is available in a range of efficiencies, from about 10% in the lowest efficiency thin film solar panels to SunPower’s high efficiency products, which are two to four times more efficient than thin film and up to 50% more efficient than standard efficiency solar technology.

The efficiency of a panel is always lower than the efficiency of the solar cells used in that panel. This is primarily because glass is used to cover and protect the cells in the panel, and glass reflects light, preventing some of the sunlight from reaching the cells.

The example below shows the mathematical formulas for determining how 22.2% efficient cells produce a 20.9% efficient panel:

• If, by shining 1,000 Watts of light directly onto a number of cells, you generate 222 Watts of electricity, then you can measure the efficiency of the cells to be 22.2%.The formula is 222/1,000 = 22.2%.
   
• Now, what if those 22.2% efficient cells were used in the manufacture of a solar panel, with glass placed over the top of them? If you then exposed that panel to 1,000 Watts of light, approximately 60 Watts of the light will be reflected by the glass, and only 940 Watts of light energy will hit the cells. Since the cells receive less light, they will produce less electricity. This is the formula for calculating how many Watts the panel will produce: 940 Watts x 22.4% = 209 Watts. Applying the formula in the previous example (209/1,000 = 20.9%), you can determine that the panel is 20.9% efficient.

Panel construction, shading, temperature, mounting and positioning are all factors that affect the amount of power generated by an installed solar power system, but high solar cell efficiency helps ensure that the number of kilowatt hours generated by a system is maximized, maximizing the cost savings realized by the system owner.

Here is an informative interview with SunPower’s founder and president emeritus Dr. Richard Swanson in which he explains SunPower Maxeon solar cell technology.

If you have any additional questions about solar panel or cell efficiency, please post them to our Facebook page or leave them below.

Play for your chance to win a $25,000 SunPower solar energy system installation and much more!

This summer, SunPower is introducing the Solar Discovery Game, an interactive online trivia contest hosted on Facebook that promotes solar energy education and awareness in the U.S. By playing, you can win the grand prize of a complete SunPower solar energy system worth up to $25,000, and will be entered to win more than 60 featured prizes, including plane tickets, video cameras, gift cards, event tickets, SunPower gear, and much more! As the grand prize winner, you can win the SunPower solar installation for your home, add to your existing system, or gift it to your family, friends, neighbor or a local community building, such as a school or recreation center. 

Playing the game is simple. Just visit the Solar Discovery Game on Facebook and answer trivia questions to earn panels (or points) towards the grand prize. You’ll earn “virtual badges” for unlocking achievements along the way and can share your progress with your friends. Each week, we’ll add new questions to answer and new prizes to win.

We’ve collaborated with some of our partners to bring a variety of prizes and contest questions. These partners include the Solar Energy Industries Association® (SEIA®), Del Monte Foods, eBay Green Team, Hawaiian Airlines, Jersey Gardens, California Academy of Sciences and Bay Area Rapid Transit (BART).

With the Solar Discovery Game, we hope to inspire our growing social media community to discover more about emission-free solar power, and share that knowledge virally with friends and family. We’re also looking for you to get involved and tell us what questions you’d like to see in the game. Submit your questions below and we might include them in the Solar Discovery Game!

The contest will run throughout the summer, from June 21^st to September 14^th. We will annouce the winner on September 16^th. Spread the word about solar and ask your friends and family to test their solar skills with the Solar Discovery Game! The sooner you begin playing, the sooner you’ll begin racking up panels towards the Grand Prize. Play now!

---

The Solar Discovery Game is sponsored by SunPower Corp. and available to legal residents in the 50 U.S. states and the District of Columbia.  The promotion starts on June 21 and continues through September 14.  Employees, directors and officers of SunPower Corporation, and any of their respective affiliates, parents, subsidiary companies, and advertising and promotion agencies and members of the immediate families and/or those living in the same household of any of the foregoing are not eligible.  Visit Official Rules to learn more detail about Solar Discovery Contest.

(And read about them soon in the next edition of Guinness World Records…!)

For years, SunPower has focused research and development efforts on offering the most efficient solar cells and panels on the market. As a result, SunPower solar panels allow customers to take best advantage of limited roof or ground space to produce significantly more electricity, and reap significantly more savings. Do you think we’re satisfied?

Well… records are meant to be broken, even our own. We are proud to introduce the E20 Series of solar panels, SunPower’s newest record breaking solar technology, and a new industry benchmark. The new E20 Series sets a new standard for solar, achieving record panel efficiencies of 20 percent or more.

The efficiency of the E20 has been verified by the U.S. Department of Energy’s National Renewable Energy Laboratory and none other than Guinness World Records! We’re very proud to receive our certification of the record from Guinness at a ceremony in Germany.

Following are some of the features of the E20 solar panel:

• SunPower Maxeon™ solar cell technology. Our revolutionary patented, all-back contact, 22.4 percent efficient SunPower Maxeon solar cell technology currently holds its own world record in efficiency for mass-produced cells. As a result, SunPower solar panels deliver up to 50 percent more energy than conventional panels.
• Anti-reflective coating to increase sunlight absorption. E20 panels capture more light to further maximize solar power generated.
• Full compatibility with the most efficient inverters. Inverters convert direct current (DC) electricity from a solar system into alternating current (AC). E20 panels can be used with inverters that require transformers, which are common in North America, as well as the more efficient transformer-less inverters that are now popular in Europe.

What does all this mean to our prospective customers? The key value proposition of the E20, as well as our existing E19 and E18 solar panels, is to generate the greatest energy savings for our customers. The E20 Series is available in Europe and Australia this year, and will come to North America and Asia in early 2012.

Check out this video about SunPower E20 Solar Panel.

On May 25^th, 2011, San Francisco Interim Mayor Edwin Lee and Supervisor David Chiu joined One Atmosphere, Luminalt and SunPower to dedicate a 28-kilowatt AC SunPower solar rooftop system at Telegraph Hill Neighborhood Center in San Francisco. With collective efforts from artists, businesses, environmentalists, government workers and more than 100 community volunteers, the new 28 kWh AC SunPower system provides a great example of how government, local business, artists, and the community can come together to accomplish something truly meaningful.

This solar installation will not only reduce Tel-Hi Neighborhood Center’s energy consumption by more than 85% but also offer the opportunity to educate children and others on the benefits of solar energy through an interpretive greenhouse.

Check out the interview below with Nestor Fernandez, the Executive Director of Tel-Hi Neighborhood Center, to find out why he believes this green initiative is a big step for the entire community.

If you’d like to receive latest solar PV technology updates, please join the discussion on our Facebook community or follow us on Twitter (@SunPower).