What time of year do solar panels output energy?

February 08, 2017

|

Click here to get more.

Lighthouse Solar

As an owner of a solar system or when considering going solar, it’s helpful to understand what your system will output over the course of the four seasons. Here in the northeastern United States, we do see significant variation in daily energy solar output from our systems over the course of a calendar year.

Solar Power Generation in Summer vs. Winter

Solar panels generally produce about 40-60% less energy during the months of December and January than they do during the months of July and August. This means that solar power generation is significantly less during the winter than it is during the summer. 

Solar Panel Annual Energy Output

Based on real data from the Lightgauge monitoring systems we install for our customers, we can closely track each system’s energy solar output variation during the year. If we split the year into two equal parts at the Vernal and Autumnal Equinoxes (March 21st and September 21st) we can get a quantitative handle on this variation.

• On average, 65% of our local solar system’s annual energy output is generated between March 21st and September 21st of each year.
• The other half of the year, between September 21st and March 21st, accounts for the other 35% of annual solar output.

Furthermore, if we take a look at the two-month windows surrounding both the Summer and Winter Solstices (June 21st and December 21st) by comparing system solar outputs for June and July vs December and January we can further accentuate the seasonal variation. 

Why Do Solar Panels Produce Less Energy During Winter?

The factors involved in this variation are threefold:

• Shorter days - Winter days are significantly shorter than Summer days. This means that the solar system will be running for less time each day and therefore produce less average energy per day.
• The angle of the sun - Compounding the effect of the shorter days is the fact that the sun angle changes dramatically in the winter as well. The sun, even at its peak around midday, is much lower in the sky during the winter months. For most residential rooftops this means that the sun’s rays will be hitting the solar panels less directly than during the summer months. This will cause the system’s power output to be lower which also has a direct impact on energy production.
• Atmospheric conditions - Not only do the winter months provide plenty of stormy weather and cloud cover, but the effect of snow cover on the panels after a storm is significant as well. With a thin covering of snow, the system will often still be able to turn on and output a small amount of energy. Larger snow accumulations on the panels, however, can keep the system from converting energy for up to a few days until the panels clear.

Does Lessened Solar Production in Winter Increase Energy Bills?

So how does this work with your utility billing? Won’t this cause system owners to get high electricity bills all winter long when their systems are under-producing and their usage is increased due to more time in the house, higher lighting loads, etc.? Not necessarily, and this is where net metering comes into play.

When we design solar systems for customers we always look at the total annual electricity usage when sizing the system. For customers with adequate roof space (or area for a ground mount) this allows us to design a system that overproduces enough during the spring, summer, and early fall to build up a bank of kilowatt-hours with the utility, which will carry the homeowner through the winter months, and the effects of reduced energy production during our northeastern winters can in fact be mitigated through correct system design, sizing, and net metering.

With competitive price and timely delivery, BEBEST sincerely hope to be your supplier and partner.

Do Solar Panels Work On Cloudy Days?

The assumption that solar systems can’t work when it’s cloudy is untrue. Solar panels do produce energy on days that are cloudier. However, the amount of energy produced on such days is at a lesser percentage than a clear day. Solar panels can usually generate around 10-25% of their standard energy production when it is cloudy. This percentage can also vary based on how cloudy the weather really is. That’s where net-metering can help. Similar to how net-metering can store energy for the winter months, it can also help provide you with the energy you need on cloudy days.

What We Advise

This is also why, for our customers who get their systems interconnected in months other than March and April, we advise them to utilize their utility’s “Anniversary Date Change” process to make sure that they are optimizing the use of their net-metered energy credits over the course of the year. If you’d like to learn more about optimizing your anniversary date please call Lighthouse Solar and speak with one of our Technical Sales Engineers.

Call Lighthouse Solar at (845) 251-2012 or contact us online to learn more about the seasonality of solar production!

Regardless of what time of year it is, switching over to solar energy is a savvy investment in your home or business. Being able to harness the immense energy of the sun and put it to work powering your home can help you save a bundle on your energy costs. However, as the year ticks by, seasons change, making it important to know the solar panel output in winter vs summer.

Solar Panel Output in Winter vs. Summer

During the winter, solar panels will produce an average of 50% less energy compared to the summer. Less output is produced in the winter because the panels have less exposure to the sunlight. They will still work during the winter, but the output will be much larger during the summer months with additional sunlight.

Influences on Solar Energy Production

In a perfect world, your panels would produce the exact same amount of energy every single day, giving you full control knowledge over how much energy they produce and allowing you to tailor your power demands to match. However, there are plenty of factors that change how much energy your panels produce, and many of those factors are dependent on the season.

These factors include:

• Geographic location - Our geographic location, and change in seasons has a significant influence over the amount of daylight your panels will see each day. The shorter days in the winter and fall will decrease solar energy production. It’s pretty easy to notice how much quicker the nights seem to get dark during winter months, and yes, that will have an effect on your solar panel system’s production. Fewer hours of daylight means less time for your panels to produce energy, which then means you’ll need to rely more on public utility energy.
• Time of day - Daylight hours tend to shift during winter months as well, and this isn’t necessarily due to daylight savings time coming to an end. When winter sets in, the sun rises later in the morning and then sets earlier in the evening, which does change how much power your solar panels can produce. It alsochanges the time at which your system will change over to public utility energy, which could influence how much your energy costs.
• Time of year (season) - The longer days of summer allow us to generate more solar power which can be stored and used on days that are shorter when there is less energy generated.
• Landscape - With the sun setting earlier comes concerns as to where your home is located. California isn’t exactly a flat state, and while the Central Valley has miles and miles of sprawling farmland, there are areas in the mountains that could find themselves in shade sooner than an area out along the coastline. These areas in particular are hit harder by the faster-setting sun, as they lose their direct sunlight sooner than others.
• Atmospheric conditions - It’s no secret that winter is subject to more days of cloudy or even rainy weather. These conditions reduce the amount of sunlight your panels are exposed to, which in turn limits the amount of energy they can produce. This doesn’t mean your lights will turn off on cloudy days, but it does mean that you may find yourself relying on more power from the public grid than you would during a clear day without a cloud in the sky.

What to Expect From Solar Production In Winter Months

So this brings up the question: does solar become essentially useless during winter months? The answer: absolutely not, in fact quite the opposite. For starters, solar panels actually run more efficient during cool winter months because the cool weather allows for a more even flow of electricity from your panels into your home. Likewise, the colder weather actually helps keep your panels cool, which increases their lifespan and longevity as well.

Nations like China, Germany, and Japan are all world leaders in solar energy, and they’re all significantly further to the north than California is. That means you can still enjoy the benefits of solar during winter, just to a different level. For example, many California residents will take advantage of friendly net-metering laws to build up a substantial credit during the summer months when their panels produce the most energy, and then use the credit to help offset the increased utility bill costs during winter.

For more information about solar power during the winter months, talk to the experts from SunPower® by Quality Home Services by dialing (800) 496-3074 today or filling out our online contact form!

If you want to learn more, please visit our website 15w solar panel exporter.