How does winter affect solar panel productivity?

Commercial solar projects are often analyzed based on their annual performance: electricity generation in kilowatt-hours and the corresponding dollar amount the homeowner can expect to save. This approach is useful when presenting a quick financial overview of a commercial solar project: high-quality PV modules can last more than 25 years and a month-to-month cash flow would be more than 300 lines.

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Annual cash flow projections are convenient, but commercial solar owners should be aware that sunlight conditions change throughout the year. A 220 kW solar panel may have an estimated annual output of 300,000 kWh, but that doesn't mean the owner will get exactly 25,000 kWh per month. This is the average monthly production, but actual monthly production varies throughout the year due to changing sunlight conditions:

• Abundant sunlight results in above-average production during the summer.
• Low sunshine results in below-average production during winter.

Commercial solar system owners should also be aware that the productivity of photovoltaic modules decreases over time. If you compare the electricity production of a given month over several consecutive years, you will notice that the productivity gradually decreases. However, quality solar panels typically have a productivity loss of 2-3% during the first year and then less than 0.50% per year thereafter. You can now find solar modules that still have more than 85% of their initial output after a 25-year lifespan.

Solar Generation in Winter: Using the World Bank's Global Solar Atlas

The Global Solar Atlas is a very useful tool from the World Bank Group that provides detailed information about solar resources at any project location. This includes an estimate of annual productivity in kWh/kWp (kilowatt-hours per kilowatt-peak of solar capacity) and a breakdown of monthly productivity.

If you research locations in and around New York City, you will find that solar panel productivity is typically between 1,300 and 1,500 kWh/kWp per year. For the owner of a 200 kW solar panel, output can range from about 260,000 to 300,000 kWh per year.

Keep in mind that these are general productivity numbers based on solar maps. To determine the productivity of a commercial solar panel in a given location, you need a professional feasibility study and PV system design . However, approximate numbers are useful as a starting point.

Comparing Solar Panel Productivity in Summer and Winter

Suppose you plan to install a 200 kW commercial solar array generator, and the Global Solar Atlas shows an estimated electricity production of 275,000 kWh/year (275 MWh/year) for your site. However, this production is not evenly distributed throughout the year, and the Atlas presents the following results:

In this case, July is the most productive month with an electrical production of 26,900 kWh, while December is the least productive month with only 15,800 kWh. In this case, the electricity production of the most productive summer month is 11,100 kWh higher (70% higher) compared to the least productive winter month.

• Considering 275 thousand kWh/year, the average monthly production is 22,917 kWh.
• The months where the estimated production comes closest to this value are September and October, with estimated productivity values ​​of 24,100 kWh and 21,400 kWh.

Having greater solar production during the summer is convenient as it helps to compensate for high air conditioning loads. Solar productivity decreases during the winter, but buildings also use less electricity on average. Most air conditioning systems are all-electric, while space heating systems often rely on natural gas and heating oil. However, this is starting to change with the increased use of all-electric heat pumps .