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Should You Size Your Solar Panels for Winter or Summer?

Published Aug. 02, 2023

Solar energy systems remain the best way for homeowners to save money on their electricity bills while reducing their home’s carbon footprint. They reduce homeowners’ dependence on utility companies and help shelter them from the effects of ever-rising electricity costs.

But solar energy systems aren’t one-size-fits-all. It’s crucial that your solar system design is optimized for ideal energy production. And new 2023 regulations make optimal sizing more important than ever for homeowners in California.

Seasonality is a crucial element when sizing a solar panel system. We at Citadel always educate our prospective solar customers on this topic.

In this blog post, we’ll explore the following:
  • How solar energy production varies between seasons
  • Pros and cons of sizing for winter
  • Pros and cons of sizing for summer
  • 2023 regulations that impact ideal system sizes in California
  • The impact of adding a solar battery
  • How to find your right system size

Understanding Seasonal Variations in Solar Energy Production

Solar energy production isn't consistent throughout the year. There are fluctuations tied to the changing seasons.

Let’s discuss some of the factors surrounding solar’s seasonal productivity. We’ll focus on the northern hemisphere.

Sun position—Sunlight angles vary seasonally. In summer, the sun sits higher, providing more direct sunlight for maximum energy production. Conversely, the sun sits lower in the sky in winter, resulting in less direct sunlight and reduced energy production. 

Daylight hours—Summer’s longer daylight hours give more time for your panels to absorb sunlight. This increases overall energy production compared to the shorter days of winter.

Seasonal shading—Ideally, sunlight’s path to your solar panels should not be obstructed by trees. If it is, there are seasonal factors to consider. Dense foliage in the summer can partially block sunlight and decrease energy production. Trees that lose their leaves in the fall will cast less shade during winter, improving energy production.

Does summer heat lead to more solar energy production?

You might be surprised to learn that higher temperatures do not increase solar energy production. While other aspects of summertime conditions increase overall energy production, high heat can actually slightly reduce your solar system's efficiency.

The good news is that when high temperatures strike, you’ll enjoy your air-conditioned home with far lower utility bills and with far less impact on the environment.

Overall, solar panels are most productive in summertime conditions.

But the question remains: What season should I size my solar panels for?

Sizing Your Solar Panels for Winter: Pros and Cons

A solar system sized for winter is larger than one sized for summer. This is because more panel wattage is needed to produce a given amount of energy in winter than in summer.

Pros of sizing your panels for winter:

  • Your solar production will meet your energy needs in winter, reducing your reliance on the grid.
  • Your system will produce sufficient solar energy year-round, including days with lower sunlight intensity and fewer daylight hours.

Cons of sizing your panels for winter:

  • Your system will overproduce energy during other seasons. Selling that excess energy to energy companies (the grid) may not be lucrative (see How New 2023 Regulations Impact Your Ideal System Size).
  • Larger solar panel systems tend to cost more.

Note: You cannot significantly oversize your solar panel system relative to your past 12 months of energy usage without justification. California IOUs (Investor-Owned Utility Solar Photovoltaic (PV) Programs) can reject an interconnection application if the solar system is deemed too large.

Sizing Your Solar Panels for Summer: Pros and Cons

A smaller solar system—one sized for summer—offers its own advantages and disadvantages.

Pros of sizing your panels for summer:

  • Your solar production will meet your energy needs in the summer.
  • You will enjoy lower electricity bills year-round compared to not having solar.
  • Smaller solar panel systems tend to cost less.

Cons of sizing your panels for summer:

  • For the rest of the year, you will need to purchase more electricity from the grid due to lower energy production.
  • You will have less independence from utility companies, particularly if you add more electric-powered appliances to your home.

How New 2023 Regulations Impact Your Ideal System Size

California homeowners are impacted by Net Energy Metering (NEM) 3.0. Since April 15, 2023, this bill has dictated how excess solar energy is credited to homeowners.

The most notable impact is that the average export rate—the amount that energy companies pay homeowners for their excess solar energy production—was reduced from $0.30/kWh to $0.08/kWh.

What does this mean for you?

Because the financial incentive for solar energy overproduction is now smaller, it’s often best to build a smaller (summer-sized) solar panel system.

Most prospective solar panel system owners should optimize to use all of the power generated by their solar panels and export little or no energy to the grid.

For systems without any solar batteries, payback is generally optimized when it is sized to produce 60–80% of the homeowner's past 12 months of electricity usage.

Are California’s NEM 3.0 changes retroactive?

No, the changes do not impact homeowners who owned solar before April 2023 unless they increase their system size by 10% or 1kW (whichever is larger). Adding a solar battery also will not affect their NEM 1.0 or 2.0 lock-in status.

Speaking of batteries, solar batteries can greatly increase your ROI on solar—especially following the rollout of NEM 3.0.

What About Solar Batteries?

Solar batteries (also known as solar energy storage or home batteries) are devices that store excess electricity generated by solar panels for later use. They can be installed outdoors or indoors, and are most often installed in garages.

Key benefits of solar batteries include…

Increased utility savings—Home batteries enable you to store excess energy produced during sun hours. You’ll then use that energy in the evenings when electricity pricing tends to be at its highest.

Protection from power outages—Your solar battery will detect a loss of grid power and switch to stored energy automatically, keeping your home powered.

Added insights—Your solar battery system can help you monitor your energy consumption. You can use these insights to make behavioral changes that further decrease your electricity bills.

The Role of Solar Batteries Post-NEM 3.0

Solar batteries capture and store the excess energy your solar panels generate rather than selling it back to the grid. Because NEM 3.0 makes selling energy to the grid less profitable, this is a huge advantage.

In other words, under NEM 3.0, it’s better to use the excess energy you generate rather than sell it to the grid. Solar batteries enable you to do this.

Whether you size for winter, summer, or somewhere in between, home batteries can drastically increase the return on your solar investment.

Finding Your Right Size

Clearly, there is much to consider when sizing a home solar system. Seasonal variations in productivity impact your ideal size. If you’re in California, you must also account for the impacts of NEM 3.0.

And there are even more factors that influence your solar system’s size: Your energy consumption, your goals, your home’s roof size and shape, and more.

But don’t be overwhelmed. Instead, leave it to the experts. A great solar team will ask you the right questions and design an optimized solar system for you and your family.

If you’re in California, we at Citadel are here to help you meet your savings and sustainability goals. For a free quote and answers to all your solar questions, get in touch with us.