Is Solar Efficiency Important When Buying Panels?

If you’re looking at solar, one of the first things that you come across in your research is probably what type of panels to purchase. Like any product on the market, performance is measured by how well the product does what it is designed to do. With solar panels, that means converting sunlight into energy you can use to power you home. This is what is called solar efficiency, and efficiency ratings are a key metric when selecting a solar panel brand for your project. This factor is indicative of the quality of the panels you’re purchasing.

Check out this video from Energy Sage on Why Should You Care About Solar Panel Efficiency?

How is efficiency different from panel wattage?

When quoting an initial solar proposal, your solar salesperson will include what type of panels (1) you have selected or (2) that he recommended based on your preferences. The panel of choice will include a manufacturer name, model and wattage. Wattage refers to watts per hour in direct current (DC) that the panel is capable of producing in ideal conditions.

When sunlight enters a solar cell, it produces a direct current (DC) and then passes through a solar inverter into alternating current (AC) to become usable energy. Efficiency, on the other hand, deals with what % of usable power is left over after that energy has been converted. They are both important factors to consider, because they deal with overall power and performance of your new solar system. To read more about how solar energy works, click here.

What type of efficiency ratings should I be looking for?

It is well known that the price of solar panels has dropped dramatically over the past decade. Solar energy is now an affordable alternative energy source for most homeowners today. It is a viable investment because of its cost in comparison to the high cost of power in some states, particularly California. Advancements in technology lead to product cost dropping, and when it comes to solar–efficiency is a major factor. Efficiency has been improving at a rate of about .5% each year since 2010.

According to an article written earlier this year, What Are The Most Efficient Solar Panels, “…the majority of solar panels are 16 percent to 20 percent efficient at converting sunlight into electricity” ( If the average efficiency rating is around 18%–that means when the sun hits the panels, only 18% of that sunlight would convert into usable energy.

Panels Ranked by Efficiency

  1. Sunpower X22 – 22.8%
  2. REC Alpha Series – 21.7%
  3. LG NeON 2 – 20.3%

Sunpower leads the market when it comes to top-performing panels. Their X22 panels have the highest efficiency rating to date at 22.8%. Their premium products have a slightly higher price tag, but if you’re looking for the best in solar performance– sunpower is it.  LG and REC are two very reputable brands that offer an alternative, more affordable solution for consumers in search of high quality solar panel options.

Will more efficient solar panels last longer?

Solar panels with the highest efficiency ratings will be the least affected by what is called degradation. However, all panels will degradate– or lose efficiency over time. Solar customers will lose about 1% efficiency every year due to: damage from intense sunlight, heat, and thermal cycling. What does that mean to you as a consumer? Most solar manufacturers guarantee 80% output at year 25. Recently, more reputable brands have been increasing it to as high as 90% output, i.e.  Sunpower and LG. A 5% difference in production at your 25 on a 5 kW system would equate to about 350 kW per year at year 25.  The current value of 350 kW per year is about $80 per year.

At this point, the solar manufacturer warrant period will end. This is because the panel manufacturer can’t guarantee your panels will maintain a certain level of production. However, panels are made to last longer than most people will live in the home.

In summary, solar panel efficiency is indeed an important factor to consider when selecting a panel product but it shouldn’t be the only one. Remember these key takeaways from our article when meeting with your solar provider of choice.

During your initial consultation, ask them what efficiency the panels they included in your solar proposal are.

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