We broke our scoring down into five categories. Each category awards up to three points, allowing up to 15 points total. Here is an explanation of each of these categories and why they are important factors to consider when evaluating solar panels for homes:
Solar panel cost
The cost of solar panels is by far one of the most important considerations for consumers, and for good reason. Solar panel costs can range from a few hundred dollars into the thousands. To ensure that our reviews of each solar panel remained clear and relevant for all consumers, we looked at the average cost range per module (or per panel). Based on our research, the average cost of a solar panel by module checked in around $322 per panel.
Based on this average, we broke down ranking the cost of solar panels in the following way:
- 3 points – Less than $320
- 2 points – $321 – $450
- 1 point – More than $450
Solar panel temperature coefficient
A solar panel’s temperature impacts how much power it can efficiently generate. This is why it’s important to measure a panel’s temperature coefficient, which is how well a panel will operate in warm climates. The temperature coefficient is expressed in the percentage decrease a panel will experience for every degree increase in temperature above 25 degrees Celsius (77 degrees Fahrenheit). The lower the temperature coefficient, the better a solar panel will operate. Most solar panels have a temperature coefficient of around -0.3%.
Based on this, we broke down our ranking of temperature coefficient like this:
- 3 points: -0.29% or lower
- 2 points: -0.3% to -0.35%
- 1 point: -0.36% or higher
Solar panel warranty
The warranties on solar panels are important because they guarantee that the panel will operate efficiently for a certain amount of time. In the solar industry, the warranty is split into two: a panel’s performance warranty (how well it generates electricity) and a panel’s material or product warranty (that the panel itself does not have any defects or issues). The industry standard for the performance warranty is 25 years. The product warranty usually sits between 15 and 20 years, although newer solar panels often have material warranties of between 20 and 25 years.
Based on this information, we awarded warranty points in the following way:
- 3 points: 25+ years performance warranty and 21+ years material warranty
- 2 points: 25 years performance warranty and 16-20 years material warranty
- 1 point: 25 years performance warranty and 15 or less years material warranty
Solar panel efficiency
A solar panel’s efficiency measures how well a panel converts sunlight into electricity that can power your home. Solar panel companies provide an efficiency range that the panel will operate within. For example, the Panasonic EverVolt solar panel’s efficiency ranges from 20% – 21.7%. For the purposes of this guide, we looked at each solar panel’s maximum efficiency. Most solar panels operate at a max efficiency of around 20.5% – 21%. By far the most efficient solar panel on the market currently is the SunPower A-Series with a max efficiency of 22.8%.
Based on these industry standards, here is how we scored solar panel efficiency:
- 3 points: 21.1% or higher
- 2 points: 20% – 21%
- 1 point: 19% or lower
Solar panel materials
There are different types of solar panel materials on the market, with the three main types being monocrystalline, polycrystalline, and heterojunction. Currently, heterojunction and monocrystalline solar panels are the most efficient types and generally have the highest output levels. Polycrystalline and amorphous panels normally cost less, but also have lower efficiency levels.
Using this information, we ranked the top solar panels in the following way:
- 3 points: Heterojunction and Monocrystalline
- 2 points: Monocrystalline
- 1 point: Polycrystalline or Amorphous