Can I Add Solar Panels to an Existing System?

As a homeowner in California, you may already enjoy the many benefits of solar energy to power your home. The reduction of your energy costs, the positive impact on the environment, and the satisfaction of being energy independent are just a few of the perks. So what can you do if your energy needs have changed since your solar system was first installed? The good news is that you can add solar panels to an existing system, and doing so can be a helpful way to further decrease your utility bills and maximize the benefits of this renewable energy source.

When to Consider Expanding Your Solar Energy System

Life’s a journey of constant evolution, and our energy needs are no exception. As we adapt to new ways of living, our energy consumption patterns change. For instance, the worldwide shift to remote work has led to increased energy use at home. Similarly, the adoption of electric vehicles (EVs), the addition of a pool, or more home appliances can all lead to increased energy consumption.

Generally, homeowners can evaluate the need for system expansion about a year after their solar power installation. This period provides ample time to observe the performance of their solar panels and the usage of the utility grid across different seasons. If you notice that your energy consumption surpasses the energy production of your solar system, it might be time to consider expanding your system to meet your current energy requirements.

If you moved into a brand-new home equipped with pre-installed solar panels, you might need to add your existing system. Often, new homes come with a solar system that’s designed to meet the bare minimum requirements stipulated by solar mandates, rather than the specific electricity needs of the homeowner who moves in. Once you’re accustomed to your new home and have a clearer understanding of your solar energy production versus energy consumption, you might consider enhancing your electricity coverage by installing additional solar panels.

Determining the Number of Additional Solar Panels

The process of adding more solar panels to your current installation will depend on your current energy usage. A Solar Technologies solar energy consultant can review your historical solar monitoring information and electricity bills to determine this. If you know you have changes coming soon – such as the purchase of an electric vehicle – these factors will need to be taken into consideration.

You might also have concerns about the remaining space on your roof for additional solar panels or how the aesthetic of the system might alter with expansion. Be assured, a custom designed system, like our team at Solar Technologies creates for add-on solar projects with an 8-panel minimum, will be created to seamlessly blend your new and existing solar panels, taking into account the available space and optimizing placement to enhance your electricity production.

Compatibility of New Panels or Battery Storage with Original System

When you start the process of expanding your system, your provider will conduct a thorough assessment of your current setup. Given that solar systems are engineered to last for decades, the need to replace an entire solar system in order to add additional panels is a rare scenario. However, the age of your home solar system might require an upgrade of certain components to facilitate your desired expansion.

Every photovoltaic (PV) solar panel is equipped with microinverters, a feature that makes them perfectly suited for a modular setup. This means the integration of additional solar panels into the existing solar system and the solar monitoring process can be accomplished with ease. However, if your solar system has aged and isn’t compatible with the expansions you want, you might opt to either completely replace the current system or install a separate system alongside your existing panels.

Choosing a Solar Installer for Expansion

Choosing the right solar installer for your expansion project is crucial. If you had a positive experience with your original installation company, it might be beneficial to stick with them. They will already be familiar with your system and property, which can streamline the process.

However, there may be circumstances where sticking with your original installer isn’t feasible, such as if you had a less than satisfactory experience with them or if they have since gone out of business. In these cases, you can shop around for other installers to add more panels to your solar array. However, finding a solar company willing to do this work may present a challenge. Some installation companies hesitate to take on add-on projects for systems they didn’t originally install for two reasons: potential warranty conflicts and the size of the project.

In terms of warranty conflicts, some installers may be wary of getting entangled in disputes down the line regarding who is responsible for fixing a part of the system, especially if the original work was not their own and they can’t vouch for its quality.

When it comes to project size, many installers have a minimum system size they will install to ensure their profit margins. For example, an average add-on solar project might consist of installing only a few panels, and that may not meet the minimum requirement. At Solar Technologies, there are a few factors that come into play and we too have a minimum add-on minimum requirement. It is best to give us a call or reach out to see if your solar expansion will qualify. 

California’s NEM Program and Solar Expansion

California’s Net Energy Metering (NEM) program allows homeowners to receive bill credits for the excess solar energy they generate and feed back into the grid. If you’re considering expanding your solar system, it’s essential to understand how this could impact your NEM benefits – especially in California with PG&E’s new Solar Billing Plan.

In California, homeowners can expand their solar system by up to 10% while still maintaining their eligibility for the benefits of the NEM 1.0 or NEM 2.0 programs without any changes. Existing customers of these programs are protected by a grandfather clause that ensures they can continue to reap the full benefits of NEM 1.0 or NEM 2.0 for 20 years from their solar installation. Remember, this 20-year period starts on the Permission to Operate date from your initial solar panel installation, not when you choose to expand your system with additional panels.

Forecasting our energy needs 10 years down the line is challenging. Yet, the ability to enhance your system with additional solar panels or battery storage in the future gives homeowners peace of mind. It instills confidence knowing that your investment in a home solar system isn’t just beneficial today, but also flexible enough to cater to your energy needs in the future.

Factors to Consider When Adding New Solar Panels to an Existing System

When considering adding new solar panels to your existing system, there are several factors to keep in mind:

Your Home Energy Needs and Rooftop Space

The number of additional panels required for your system depends on several factors, including your post-solar electricity bill, geographical location, equipment, and system design. If you can provide your installer with your electricity bill details since going solar, they should be able to determine the number of additional panels needed for your unique circumstances.

For those with rooftop systems where space is limited, expansion might not be feasible. 

Evaluating Solar Panel Upgrades and Compatibility

The type of panels used in your original installation and whether any component needs an upgrade are important considerations. Solar panels are designed to produce electricity for more than 25 years, with significant dips in production likely only after this period. As a result, it’s unlikely that you’ll need to replace the panels from the original system. However, it’s still advisable to have your installer inspect all components, including the racking and wiring.

When incorporating new panels, it’s advisable to choose the same type as those in your original array if you can. This will help maintain an aesthetic consistency and ensure comparable power outputs and efficiencies. If it’s not possible to install identical panels, try to install new panels with a power output that’s comparable to prevent any harm to your existing array.

Inverter Replacement

Based on the amount of new capacity you add to your system, you may also need an inverter replacement. The dimensions of your central inverter is calculated based on the power output of your panels. If you’re incorporating a substantial number of panels and the total size of your solar system significantly exceeds the original size, your existing inverter may not be equipped to manage the surge in electricity production.

Add-on projects are somewhat simpler if your original solar panel system uses microinverters instead of a power optimizer or string inverter system. You can eliminate concerns regarding inverter capacity problems because microinverters are located at every individual solar panel, which allows for the installation of additional microinverters with your new panels.

Permitting and Interconnection

Installing additional panels on your property might require additional permits or the submission of more interconnection documentation to your utility company. This depends on several factors, including the number of additional panels you’re adding, whether a new inverter is required, and your local permitting requirements. If you’re adding more than a few kilowatts (kW) to a solar system and need to replace your inverter, you’ll more likely have to submit another interconnection application with your local utility company.

Any installer you work with for your add-on project should know about the permits or interconnection requirements and assist in filing for these as part of the overall cost of your installation.


Regardless of how big or small your solar project is, it’s always helpful to explore your options and gather multiple solar quotes to compare. If you want to add additional solar panels to your current system, make sure you include this information in your account, along with details about your existing system (like your solar equipment, system size, etc). This will allow installers to give you the most precise quotes, tailored to your specific energy needs.

If you’re ready to expand your current solar power system, our Bay Area team has more than 25 years of experience in designing and installing the right size of home solar systems to meet your family’s growing needs. Schedule an online appointment today to learn more.

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