How Solar Module Efficiency Affects ROI

How Solar Panels Work
Solar Module Energy Production

When considering solar for your home, deciding on a type of solar panel becomes very important. Energy production starts with the solar panel. If this device isn’t efficient, then the rest of the system’s efficiency doesn’t matter. That said, how much power a solar panel produces and whether it’s efficient comes down to a couple of factors. Let’s explore them together.

How Much Power a Solar Panel Produces

Since not every solar panel has the same specs, they’ll produce different amounts of power. Both the size of the solar panel and the wattage rating play a role in the amount of electrical current an average solar panel will produce.

Solar Panel Sizes and Wattage

A residential solar panel typically covers a 65-inch by 39-inch surface area, which equals 17.6 square feet of roof space. While the average panel size hasn’t changed, the efficiency of these solar panels has increased over time. 

In 1954 the average residential solar panel generated 20 watts, whereas today’s solar panels for homes produce 320 watts. The 1954 solar panel could power one-third of a 60-watt light bulb, while today’s solar panel powers five and one-third light bulbs.

The average solar panel in 2020 produces between 285 and 360 watts, representing a large gap between production among solar panels. This gap increases with premier solar panels, which can generate up to 400 watts.

Daily kWh’s Produced by Solar Panels

The daily production of a solar panel depends on the wattage of the solar panel and the peak sun hours in the area. Peak sun hours are the times when the sun generates the most solar energy. While the sun shines throughout the day, the intensity of its radiation varies. 

The United States has an average of four peak sun hours per day. To find the kWh’s of production for a single solar panel, multiply the peak sun hours by the wattage of the solar panel. Depending on the wattage of the solar panel, it could produce between 1.14 kWh’s and 1.6 kWh’s per day. 

Importance of Solar Panel Efficiency

The efficiency of the solar panel determines how much of the sun’s rays the solar panel can absorb. Solar panels with higher efficiency percentages typically have higher wattage yields. 

Solar panels with greater efficiency often come with a greater price tag as well. However, the price difference makes it worth purchasing a solar panel with slightly lower efficiency for most homeowners. 

When the homeowner doesn’t have a lot of roof space or uses more energy, a solar array with average solar efficiency may not fit. These homeowners may have to consider paying more for solar panels with higher wattage and efficiency. 

Solar Panel Efficiency Factors

To determine the difference between solar panels, simply divide the size of the solar panel by its wattage. This equation will determine the wattage difference per square foot between solar panel types. 

E.g., a solar panel with 17.6 square feet and 285 watts can produce 16 watts per square foot, while a solar panel with the same square footage but more power at 400 watts equals 22 watts per square foot.


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