There are three important characteristics to look for in solar panels—

• panel efficiency
• panel warranty
• weather resistance

Panel efficiency means how well a panel performs over time. Solar panels lose some ability to generate electricity as time passes—the question is, how much do they lose & how fast.

High-quality panel manufacturers offer a Power Production Warranty that guarantees no more than X% efficiency loss over X years. Inferior panels tend to have a greater immediate drop-off in efficiency and a sharper production decline over the life of the system (20-30 years).

A good panel warranty should guarantee against manufacturing defects and assure efficient performance over the duration of the warranty. Superior panels offer typical 25-year warranties.

Weather resistance is a solar panel’s ability to withstand wear and tear from the elements. People often ask about hail damage, and our standard answer is, hail big enough to break car windshields will probably break a solar panel. But that’s pretty rare, and in any event, would be covered by your homeowner’s insurance. In coastal areas, salt is a big concern. Well-built panels are crafted from high-grade aluminum (6000 series marine grade, for example) and include a salt mist certification for use near the coast.

In short, you’re well advised to go with solar panels that guarantee higher efficiency over a longer warranty period.

But here’s the best advice: with the growth of the solar industry, most panels are now commodity items (except the high-efficiency panels from companies like SunPower). It is far better to spend your time choosing a good solar installer, who will recommend the best panels, than spending time weighing fine specification differences between panels. An experienced installer will know what to recommend—and will protect you (and his company’s reputation) by making good, safe recommendations and offering a strong workmanship warranty.