When thinking about powering your home with solar, it’s important to understand the concept of solar seasonality and its impact on your electricity bill: reduced sunlight during certain seasons of the year can impact the amount of solar energy that your solar panels can generate, and the amount of electricity you need to pull from the grid.
While most homeowners recognize that solar panels don't work at night, or produce less electricity when it's cloudy and raining, they don’t realize how the changing of seasons can impact solar power generation and their electricity bills. In this article, we’ll help you understand solar seasonality and why daily solar energy production can vary depending on your location and the time of year, to help you better anticipate fluctuations in your energy production and energy consumption.
What Is Solar Seasonality?
Solar seasonality refers to the variations in solar energy generation that can occur as a result of seasonal patterns in weather and sunlight coverage. Just as you expect different temperatures between spring, summer, fall, and winter, you can also expect different levels of sunlight that’s available to use for home solar power.
How Does The Sun’s Position Affect My Solar Panels?
Solar panel systems are most effective during the peak sunlight hours of the day. It’s the time of day when the sun delivers the most direct sunlight over the most sustained time frame.
That doesn’t mean your solar panels don’t work outside of that peak time frame. It just means that the power of the sun's radiation varies, based upon the sun’s brightness, sunlight angles, and the expected position of the sun during seasons or on certain days of the year. As a result, those fluctuations can alter the amount of energy your solar power system can create.
Your solar panels are set at a specific angle when installed on your roof by your solar company because that angle directly impacts solar panel efficiency, and it’s calculated based upon factors such as:
- The average number of daylight hours
- The average level of cloud cover
- Historic precipitation levels
- The angle of your roof
- The direction of your roof compared to the sun
When designing the size and shape of solar panel systems, solar installers use sun databases that are built on historical data to determine the expected solar irradiation levels for different geographic regions and adjust your system accordingly.
Average Daily Sunlight Numbers by Season
The position of the sun during each season of the Earth’s orbit is a core aspect of solar seasonality, so it’s important to know the average peak sun hours for each season. For example, here are the seasonal averages for the continental United States, courtesy of the National Renewable Energy Laboratory:
- Winter: 4 to 4.5 hours
- Spring: 4 to 5.75 hours
- Summer: 6 to 8 hours
- Fall: 4 to 7 hours
Seasonality of Electricity Consumption
In addition to changes in your energy production as a result of seasonality, keep in mind that seasonality has an impact on the amount of electricity that you consume as well. During hotter months, you may be running your air conditioning more, and during colder months, your heater use may increase your electricity demands, so your energy needs are going to fluctuate throughout the year.
If you live in an area with net metering, you may be able to offset some of your peak season electricity usage with overproduction during the more temperate months. For example, if you build up net metering credits during the warmer summer months when you’re not using air conditioning, it may help offset some of your electricity use during the colder, darker winter months when you’re using your heater and lights more.
Your energy usage can also change depending on who’s in the house, and the summer and winter months have very different energy needs. If you’re away for a week on vacation during the summer months, you’re using little to no electricity, which can help to offset future costs if you earn net metering credits. In the winter months, if you have friends and family visiting for the holidays, you may use more electricity than usual thanks to increased demand on your home’s solar system.
Why Does Seasonal Solar Panel Performance Matter to My Utility Bill?
Solar seasonality can significantly influence solar panel efficiency and performance. There is a direct correlation between the amount of sunlight your panels can receive, and the amount of electricity they can generate. (And as a result, the amount of money you can save!)
The winter months historically have shorter days which means less sunlight, and the less sunlight your panels receive, the less electricity they will create. The less electricity your panels create, the more electricity you’ll have to use from the electricity grid. And the more electricity you take from the grid, the higher your bill can be.
Even if your solar power system includes enough panels and generation capacity to meet all of your energy needs, that doesn’t mean you’ll always have enough power available every single day. Each time your home draws power from the electricity grid instead of your solar panels, your electricity bill goes up. By recognizing the different expectations for seasonal solar panel performance, you can better anticipate fluctuations in your energy bills.
How Do Different Weather Conditions Influence Solar Panel Efficiency?
Anything that gets between your solar panels and the sun can affect the amount of solar energy your system generates. This includes clouds, rain, shade from a nearby tree, and other weather-related situations. Keep in mind that just like you can still get sunburned on an overcast day, your panels will still be generating power during a variety of weather conditions, it’s just the total output that might change. Thus, it’s helpful to dig into the ways that weather can affect your solar panels:
Most people think that the more sunshine there is, the more electricity solar panels can generate. That’s generally true, but there’s more to consider. Temperature can affect the performance of many electronic devices, including solar panels.
As the temperature increases, panels can create less voltage and become less efficient in generating power. Solar panels actually work best on clear days when the temperature is under 80°F, so if it gets hotter, your performance may actually decrease.
Contrary to what you might believe, colder locations are still suitable for solar production. Modern solar panels are more efficient in cooler temperatures between 45°F and 75°F, as long as they have direct sunlight on a clear day.
Even on cloudy days when it’s raining outside, your solar panels are still working. They just aren’t generating electricity at peak efficiency. If the sun is shining in any capacity, diffuse or indirect sunlight will still reach your solar panels and create energy.
Solar panels can still produce power, even when covered in a thin layer of snow, as sunlight can still penetrate solar panels through the snowfall. While it’s good to clean your solar panels when they get dirty, a thin sprinkling of snow will typically melt quickly because of the heat generated by the panels.
While more snow can prevent a lot of your electricity generation, the angle your panels are installed at, and their slick surface can help the snow slide off once the sun comes out.
Solar Seasonality and Solar Panel Performance
Solar panels can be a good investment no matter where you live. However, it’s important to consider how seasonal solar panel performance can impact your electricity bill. The amount of sun your solar panels receive can vary depending upon the time of year, and that can contribute to the size of your utility bill.
Certain seasons of the year provide more daily sunlight than others, while other solar seasons can deliver adverse weather conditions that decrease the efficiency of your solar panels. Understanding the relationship between solar seasonality and energy generation will help you plan your usage, anticipate when you will need to use the utility grid, and budget for your total energy needs.
To find out what size solar power system is right for your home’s needs, based on location data and other seasonal factors, get started today with the free Palmetto Solar Design and Savings Tool.