Adding A Battery To An Existing Solar System
- Sarah Lozanova
- Feb 11
- 9 min read
Updated: Apr 30
Table of Contents:
Back in 2020, only about 6% of home solar systems had battery storage. Fast forward to today, and that number has jumped—by early 2024, around 25% of new residential solar installations included batteries, according to Wood Mackenzie. And in places like Hawaii, where net metering isn’t an option, batteries are practically a must-have. California has also seen a big surge in battery adoption, thanks to incentives like the Self-Generation Incentive Program and the need for backup power during planned outages.
So, why are more homeowners choosing to add a battery to their solar systems? A big reason is cost—battery prices have dropped, and some states offer rebates and tax incentives that make them even more affordable. Plus, in areas with frequent blackouts or high electricity rates, having a solar battery can mean keeping the lights on and saving money.
As solar battery storage systems become more popular, many homeowners want to add a battery to their solar systems. Solar batteries are especially appealing in areas with an unstable electric grid, such as areas regularly impacted by severe weather. Due to the utility rate structure in some areas, some homeowners can reduce their electric bills more with a battery. Let’s explore the topic of adding a battery to a solar system so you can better serve your customers.
Can I Add a Battery To An Existing Solar System?
Yes, adding battery storage to an existing solar system is not only possible but increasingly common. Retrofitting a battery bank allows homeowners to store excess solar energy, reduce reliance on the grid, and keep essential appliances running during power outages. As battery prices decrease and incentives improve, more customers are looking to add a battery to their systems.
Most solar panels are compatible with energy storage, but the ease of integration depends on the system design. If the original solar installation wasn’t set up for battery backup, you’ll need to modify it. This usually means either replacing the existing solar inverter with a hybrid inverter—such as the SolarEdge Home Hub or some of the Enphase IQ8 series microinverters—or adding an AC-coupled battery like the Tesla Powerwall 3 or Enphase IQ Battery 5P.
For adding a battery to an existing solar system with string inverters, AC-coupled battery solutions are typically the most practical option. These batteries operate independently of the solar inverter, making installation simpler. However, DC-coupled systems with hybrid inverters can offer better efficiency since they reduce conversion losses.
Why Add a Battery to a Solar System?
Adding a battery to a solar system allows homeowners and businesses to store excess energy for later use, particularly during times of peak demand or power outages. Solar panel batteries address fluctuations in energy production and consumption, offering reliability when the sun isn’t shining or during blackouts. In areas with time-of-use (TOU) rates, adding a battery to a solar system can help reduce electricity costs by storing energy during low-demand hours and using it during high-demand, more expensive periods.
Also, many regions offer battery incentives, and in places where net metering is unavailable, solar batteries become a valuable solution for maximizing solar energy use. For areas with an unstable grid, solar batteries can provide much-needed backup, offering greater energy independence and reducing reliance on the utility grid.
Considerations For Adding Solar Battery to an Existing System
When planning to add a battery to an existing solar system, there are several key factors to consider to ensure a smooth integration.
What Type Of Solar Inverter Does The Array Currently Use?
If the solar system wasn't originally designed with battery storage in mind, you will likely need to either replace the inverter or opt for an AC-coupled battery solution like the Tesla Powerwall 3 or Panasonic Evervolt AC-coupled battery. These batteries come with their own built-in inverter, making them compatible with either microinverters or traditional string inverters.
On the other hand, some homeowners may have already planned to add a battery to a solar system in the future and installed a storage-ready system with a hybrid inverter, such as the Solaredge Energy Hub. In this case, pairing a DC-coupled battery with the system would be a simple process, although this is less common.
It’s also important to assess the remaining lifespan of the existing inverter. Many string inverters have a lifespan of 10 to 15 years. If the inverter is approaching the end of its life, it may be more cost-effective to replace it with an updated hybrid inverter and consider adding a DC-coupled solution. This not only ensures compatibility with the new battery but also helps future-proof the system.
Is The Solar System AC- Or DC-Coupled?
An AC-coupled system with batteries has two separate inverters. One inverter converts the direct current (DC) power from the solar panels to alternating current (AC) power. This energy can power the house, and the excess can go to the electric grid. The other inverter works with the battery, which stores DC power.
By contrast, a DC-coupled system has a hybrid inverter that can invert current from both the solar panels and the battery. This option allows the DC current from the solar panels to directly charge the batteries. When feeding energy from the battery to the home or the power grid, it can also convert DC power to AC.
If you install an AC-coupled battery and keep the existing inverter, the upfront cost would likely be lower, but the system could be a bit less efficient. In the long run, this could add up. If your customer wants to keep their costs down when adding a battery to a solar system, it is probably the better option because they won’t have the added expense of replacing the inverter.
However, a DC-coupled solar system is a good choice if they are more concerned about system efficiency. With a DC-coupled system, the solar panels can charge the batteries directly without converting the power, reducing inefficiencies.
Solar Permit Requirements for Adding a Battery to an Existing System
When adding a battery to an existing solar system, you’ll need to meet local permit requirements set by the authority having jurisdiction (AHJ). These regulations may vary by location, and it’s crucial to check with your AHJ before adding a battery to a solar system. Many jurisdictions will require an updated interconnection agreement with the local utility to ensure the solar battery system complies with grid safety standards.
In addition to the AHJ’s requirements, the National Electrical Code (NEC) and utility companies often have specific safety standards and installation protocols for energy storage systems. For example, some utilities may require an additional disconnect switch or remote monitoring capabilities to enhance safety. It's also important to ensure the solar battery retrofit meets the proper wiring and grounding standards, as outlined by the NEC, to avoid electrical hazards.
Solar Panel Battery Capacity Needs
When adding a battery to a solar system, it’s essential to properly size the storage capacity to meet your customer’s energy needs. Start by understanding how they plan to use the stored energy. Some homeowners may only want emergency backup during outages, while others might prefer to have whole-house power during grid failures.
Whole-house backup can be expensive, especially for homes with large electrical loads, such as air conditioners, electric heating or water heaters, sump pumps or hot tubs. This makes it more challenging for off-grid systems to support heavy loads, which is why many off-grid homes limit their electricity consumption or use energy-efficient or gas-powered devices.
To size the battery storage system correctly, assess the customer's household loads and frequency of usage. Smaller battery systems can support light loads like refrigerators, furnace components, LED lights, and basic electronics, but they won’t last long with high-demand devices like air conditioners or electric heaters. When deciding on a battery solution, consider these factors to ensure your customers get the most value and reliability from their solar battery investment.
Customer Expectations When Adding a Battery to a Solar System
It's important to manage your customers’ expectations regarding the amount of electricity the battery can supply during an outage. Many customers may assume that the battery will power their entire home, but it’s often not possible to run high-demand appliances like electric water heaters, clothes dryers, heat pumps, or air conditioners without multiple batteries.
To manage energy use efficiently, many solar battery systems integrate with apps like the Tesla app for Powerwall users or mySolarEdge for SolarEdge batteries, allowing homeowners to monitor and control their energy consumption in real time. Also, solar installers often add a critical load panel to ensure essential devices, such as refrigerators, lights, and internet routers, remain powered during an outage.
Financial Benefits of Adding a Battery to a Solar System
Adding a battery to a solar system can provide significant financial savings, especially for customers in areas with TOU rates or limited net metering. TOU pricing means electricity costs more during peak hours, usually in the late afternoon and evening, and is cheaper overnight. By storing excess solar energy during the day and using it when rates are highest, homeowners can reduce their electricity costs.
Some customers may also face demand charges, which increase costs based on their highest electricity usage at any given time. With a properly sized solar battery, they can draw stored energy during peak demand periods, helping to avoid these extra charges.
Also, Virtual Power Plant (VPP) programs with utilities allow homeowners to sell excess stored energy back to the grid when demand is high, generating extra income while supporting grid stability. Many VPP programs partner with battery brands like Tesla Powerwall, Enphase IQ Battery, and SolarEdge Home Battery, offering financial incentives for participation.
Federal Tax Credit for Adding a Battery to an Existing Solar System
As of February 2025, the 30% federal tax credit for adding battery storage remains in effect. Despite initial concerns that the Trump administration might alter or eliminate this incentive, it continues to be available for homeowners installing battery systems with a capacity of 3 kWh or more. This tax credit applies to systems installed between 2022 and 2032.
However, recent policy shifts have introduced some uncertainty regarding the future of clean energy incentives. For instance, a recent executive order paused certain federal clean energy disbursements, leading to concern about the long-term status of these solar tax credits. Homeowners interested in adding a battery to their solar systems should consult with a tax professional to understand their eligibility and stay informed about potential policy changes.
How Much Does It Cost To Add a Battery to a Solar System?
Adding a residential solar battery storage system can easily cost $10,000 to $20,000. It can be more expensive if the customer needs more than one solar panel battery and they must replace their existing inverter. Usually, the cost of one solar battery installation with a ten or 13-kWh capacity starts at around $13,000, including labor.
How To Add a Battery to a Solar System
Adding a solar battery to an existing PV system involves several steps.
Evaluate Solar Energy Storage Needs
Determine your client's energy storage needs. Consider factors like daily energy consumption, desired backup duration during outages, and energy independence goals.
Choose a compatible battery storage system based on your client's energy needs and budget. Common types include lithium-ion batteries, such as those using lithium iron phosphate (LiFePO4) chemistry.
Ensure the existing inverter is compatible with adding a battery to the solar system. Some inverters are designed to manage both solar power and battery storage.
Comply with Solar Permitting Regulations
Check local regulations and utility requirements for adding battery storage to a solar system. Some areas may have specific guidelines or solar permit requirements. GreenLancer specializes in meeting solar permitting requirements. Create an account to begin shopping for solar plan sets, interconnection applications, and engineering stamps.
Install the Solar Panel Battery System
Follow the manufacturer's instructions to add the battery to the solar system. This involves connecting the battery to the inverter and configuring the system for proper operation.
Upgrade or Add a Solar Inverter
If your existing inverter is incompatible with the solar battery, you may need to upgrade it or add a separate inverter dedicated to the battery system.
Reconfigure Solar Wiring
Modify the wiring as necessary to accommodate the new solar battery installation. This may involve adding a separate circuit or reconfiguring existing connections.
Program and Configure
Program the system to operate in conjunction with the solar panels. Configure settings for charging and discharging the battery based on your preferences and energy needs. If the utility company has time-of-use rates, take this into account.
Test and Monitor Solar PV System
Test the system now that the batteries are connected to ensure proper functionality. Set up monitoring tools to track the performance of both the solar panels and the battery storage system.
Can I Use Solar Panels Without a Solar Battery?
Yes, you can use solar panels without adding a battery to a solar system. In a standard grid-tied system without energy storage, solar panels generate electricity during the day, which is immediately used in the home or fed back into the power grid. When excess energy is sent to the grid, homeowners may receive credits or compensation through net metering programs, depending on local policies.
However, adding a battery to an existing solar system enables energy storage, allowing homeowners to use solar power at night or during outages. A battery also provides greater energy independence and protection against rising electricity rates, particularly in areas with time-of-use pricing or limited net metering options.
Adding a Battery to a Solar System Could Be Right For Your Clients
Severe weather is becoming more common, causing blackouts to be more common. Due to falling solar battery prices and more energy storage incentives, many homeowners with solar systems want to add backup energy storage. Although this is certainly possible, proper planning and knowledge are critical.
GreenLancer can help installers plan energy storage retrofits. Our fulfillment partners can create solar plan sets and engineering reviews when adding a battery to a solar system. Complete the form below to learn more about GreenLancer's solar design services for installers.