If you have switched to solar energy, you have likely reduced or eliminated your electricity bill.

However, there may be a need to expand your existing solar panel system. This could be due to your initial system being undersized or due to an increase in electricity usage from new technologies (such as electric vehicles).

Adding extra residential solar panels will require a different process than when you initially installed the solar panel system. To help you explore your options, here are 7 important factors to consider.

1) Electricity requirements

Determining how many additional solar panels you need is the first crucial step. This will impact the system design and cost of the expansion project.

Several factors will influence the number of panels required. According to EnergySage, these factors include your location, equipment, system design, and post-solar electricity bill.

If you can provide your installers with your electric bill information since going solar, they should be able to assess your unique situation and determine the number of additional panels needed.

2) Room for new panels

Do you have sufficient space to accommodate extra solar panels?

For rooftop systems with limited space, you probably won’t. Ground mount systems, on the other hand, tend to offer more flexibility for expansion as property owners typically have ample sunny land available for installation.

Nevertheless, if you’ve exhausted the available roof space, it doesn’t mean that you should abandon the idea. You can explore the possibility of installing supplementary solar arrays on other structures within your property. Solar canopies such as the one pictured below are a great way to increase your home’s solar capacity.

residential solar panels

3) Incentives

Adding more panels to your system may affect your eligibility for certain benefits. Many incentives can only be claimed once per property or person.

Performance-based incentives (PBIs) can be complex for add-on projects since the incentive amounts are determined by the electricity generation of your system.

It’s always a good idea to discuss with your solar installer the incentives that you will or will not be eligible for regarding your add-on solar project. Additionally, consult a tax advisor or accountant for any questions regarding potentially eligible tax credits.

4) The type of inverter

Is your inverter capable of accommodating the additional panels?

Depending on the capacity added to your system, it may be necessary to replace your inverter. During the sizing process, installers base the selection of a central inverter on the power output of your panels.

The inverter converts the direct current (DC) electricity generated by the panels into alternating current (AC). As a result, the power rating of the inverter can be slightly smaller due to energy loss during the conversion process.

If a significant number of panels are being added, and the overall size of the solar panel system greatly exceeds the original size, it might generate more electricity than the existing inverter can handle.

For add-on projects, working with a solar panel system that uses microinverters simplifies the process compared to systems using power optimizers or string inverters.

With microinverters located at each panel, there’s no need to be concerned about inverter capacity issues. Additional microinverters can be installed along with the new panels.

5) The type of solar panel

Are the panels used in your original installation known to you, and do any parts require an upgrade?

Your solar panels will continue to generate electricity for more than 25 years, after which you may experience more noticeable declines in production. Therefore, it’s unlikely that the original panels need to be replaced.

However, it’s still advisable to have the installer inspect everything, including the racking and wiring.

If you’re adding new panels, it’s recommended to install the same type as the original array, if possible. This ensures aesthetic consistency and maintains the same power outputs and efficiencies.

If it isn’t feasible to install the exact same panels, it’s important to select new panels with similar power output. This prevents potential damage to the existing array.

6) Choice of installer

If your original installer offers additional services, it’s recommended to reach out to them first regarding adding more panels. They are already familiar with your system and property, making them the most qualified to perform the work.

However, if you had a negative experience with your original installer or they are no longer in business, finding a new installer for the task may be necessary.

Keep in mind that some installation companies prefer not to take on add-on projects for systems they did not originally install. This is partly because they want to avoid any conflicts regarding warranties or responsibilities for the overall installation.

Additionally, the size of the project plays a role. Smaller add-on projects may not be as profitable for installation companies compared to larger residential installations. Therefore, their focus is often on larger-scale projects depending on their resources and schedule.

7) Regulatory approval

Adding more solar panels to your property may require obtaining additional permits and submitting extra interconnection documentation to your utility company. The need for this depends on factors like the number of panels being added, the requirement for a new inverter, and the specific permitting regulations in your local area.

If your system’s capacity is increased by a few kilowatts (kW) and a new inverter is necessary, it’s more probable that you will have to submit another interconnection application to your utility company.

Any installer you work with should be knowledgeable about the necessary permits and interconnection requirements.  The installer will assist you in filing for these as part of the overall cost of your add-on project.