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  • Sarah Lozanova

How To Add More Solar Panels To An Existing System


Even if the system was designed to produce all the home’s power, it’s possible for energy needs to change over time. Maybe the residents now drive electric vehicles and use more electricity because they have a home charging station. Some homeowners are switching over to electric space heating with heat pumps, increasing their electricity consumption.


It isn’t rare for solar system owners to want to expand their solar systems. If the solar power system isn’t producing 100% of the home’s power and there is room on the roof for more panels, expanding the system makes a lot of sense. In other cases, simple modifications like trimming a tree that is shading the roof or adding power optimizers might be another way to boost electricity production.


Can You Add Solar Panels To An Existing System?

Yes, it is possible to expand most solar energy systems, but it isn’t always cost-effective for various reasons. In some cases, adding solar panels might be more complicated and expensive than it may seem, but it is typically feasible.


Expanding might involve modifying or adjusting part of the original system setup. For example, if the system has a string inverter and it doesn’t have additional capacity, you will need to supplement or upgrade the inverter. If the system is a ground mount, you might need to add another racking system. If the homeowner wants to add a battery bank and solar panels, it might also be necessary to install a larger inverter.


Assessing How Much Additional Capacity The Client Actually Needs

Just like solar installers size systems depending on household use, the same is necessary for expanding a solar system. First, start by evaluating the energy bills for the house since the solar panel system was installed.


Next, determine if your clients have plans to increase their electricity usage. For example, they may be getting an electric vehicle or swapping out a gas water heater for an electric model. Of course, it is critical to take the local climate into account when estimating the energy production of the expanded system.


In some cases, the homeowners can take simple steps to decrease energy consumption. For example, adding water-saving shower heads reduces the consumption of hot water. If they have an electric water heater, it can reduce their electricity bills. Likewise, swapping out inefficient appliances or electric heaters can promote energy savings.


Factors To Consider Before Adding More Solar Panels To A System

Although it is usually feasible to expand a solar array, it is critical to think it through before getting started. These are some of the top considerations during the planning phase.


Available Roof Space

It is certainly easiest to add solar panels if there is additional capacity on the roof; however, there are ways to work around this. If additional roof space is limited due to the existing panels, it might be possible to place extra panels on a garage roof, carport, shed or ground mount. However, the number of panels may be limited by available space.


Inverter Upgrades

Determine the string inverter capacity and if it can handle additional solar panel output. If not, it will be necessary to replace the old inverter.


If the solar system has microinverters, it's a bit easier to expand. Systems with microinverters have a small inverter mounted on the underside of each solar panel. You would just need to install more microinverters on the new solar panels instead of replacing the inverter.


Permits Needed

The permitting requirements will vary depending on if you are going to replace the inverter, if you need to install a pole mount, and local permitting requirements. Often, you will need to notify the utility company that you expanded your system so you can update the interconnection agreement. Check local requirements before beginning an expansion.


Battery Storage

Because the price of home energy storage systems has fallen dramatically in the last decade, many homeowners want to add battery storage to their solar systems. If you are also adding solar panels, now might be a convenient time to add a battery bank. It might be necessary to install a new inverter, depending on the type of battery you use. For example, the Tesla Powerwall 2 has its own built-in inverter and is an AC battery.


Aesthetic Considerations

It is helpful to consider what the expanded system will look like and try to match the panels' appearance as much as possible. In some cases, you might be able to install the same or a very similar model of PV modules, even if the solar panel wattage is slightly different.


If not, find solar panels with a similar appearance. If the original solar panels are polycrystalline and have a blue color, it might look odd to add monocrystalline panels with a black appearance. If the original panels have a silver frame, avoid installing all-black panels with a black frame, or else they will stand out.


Future Energy Bills

In many areas, customers will not get compensated by the power company for surplus power they feed to the grid above and beyond household consumption. For example, most utility companies will not compensate customers at the retail rate for power beyond the number of kilowatt-hours the household consumes in a year. This means that the solar system can offset use through bill credits, but these credits often expire after one year.


That means that oversizing the solar PV system will not usually result in greater energy bill savings. Therefore, it is critical to not oversize the system, or else the supplemental power output won’t provide additional benefits to your customers.


Quality Of Original System

Many solar companies are reluctant to add new panels to an old system, especially if they aren’t the original installer. They may have concern about conflicting warranties, encountering code violations, wiring errors, or low-quality installations. If your solar company didn’t install the original solar panels, it’s important to consider what issues you may encounter.


A Note On Incentives

Unfortunately, most homeowners will not be eligible for solar incentives when expanding their systems. For example, they probably cannot claim another federal tax credit. It is critical to be upfront with customers about this, so they understand the incentives before making a decision to expand their solar system.


However, there are exceptions to this rule, and it is helpful to research local incentives when applicable to determining if your customers will qualify because there may be some options available. For example, the Self-Generation Incentive Program (SGIP) in California currently provides rebates when adding battery storage to existing or new solar systems.


Alternatives To Expanding A Roof-Mounted System

If a homeowner expresses interest in expanding their solar system, it's critical to know why. This can help you determine if adding solar panels is the best course of action. Alternatively, if the solar system has a string inverter and no power optimizers, you might be able to bump up the production of the system by adding these pieces. This is especially true on shaded roofs or where the panels have different orientations.


If there is shade on the roof, is it possible to reduce this? Sometimes trimming a few branches off a tree can significantly increase energy production.


Although it won't increase the total energy production of the system, adding battery backup will allow the homeowners to have electricity during power outages and during peak hours. Even if you can’t expand a solar system, you could likely add battery storage instead.


Consider All Factors Before Expanding An Existing Solar System

If you have homeowners who want to be net-zero and they aren’t currently, expanding a current system by adding PV panels might be a great option. Adding solar panels is feasible for many households, although it might involve mounting panels in another location, such as a garage roof. Also, it might be necessary to replace the existing inverter or to install microinverters on each solar panel.


Often, expanding a solar system can be somewhat expensive, and many homeowners will not be able to take advantage of solar incentives. Make sure your customers understand if they do not qualify, so they can make an informed decision.


Want to learn more about being a top-notch solar installation company? Continue reading on the GreenLancer blog.


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