Comparing Different Types Of Solar Energy Storage Systems

Solar energy storage systems are gaining serious traction as more homeowners and businesses prioritize energy independence and backup power during outages. With the 30% federal ITC now extended to both solar and standalone battery storage—and state-level incentives in places like California, Hawaii, Illinois, Maryland, Massachusetts, and Oregon—demand is only going up.

Installers who understand the types of solar energy storage systems available, from AC- and DC-coupled setups to emerging hybrid inverters and long-duration battery tech, are in the best position to guide customers. Whether it’s sizing a residential solar power storage solution or integrating commercial-scale solar energy storage options, having a command of these technologies builds trust and adds value.

If you haven’t updated your knowledge of solar energy storage solutions recently, now’s the time. 2025 is shaping up to be a breakout year.

What Is Solar Energy Storage?

Solar energy storage is essential for maximizing the value and reliability of solar power systems. Because solar energy is an intermittent source—only available during daylight hours—solar energy storage systems allow homes and businesses to store excess energy for use at night or during grid outages.

For off-grid systems, batteries are critical for providing 24/7 power availability. In grid-tied solar energy storage systems, hybrid setups with batteries enable homeowners to maintain power during blackouts and to shift energy usage based on cost and need.

In regions with time-of-use (TOU) electricity rates, solar energy storage solutions help customers reduce utility bills by storing energy when rates are low and discharging it when rates peak. This load-shifting capability can significantly reduce the solar system payback period while improving energy independence.

Popular Solar Energy Storage Systems

Solar Battery	Battery Chemistry	Capacity (kWh)	Cycle Life	Inverter Compatibility
Enphase IQ 10	Lithium Iron Phosphate (LiFePO4)	10.1 kWh	10,000+ cycles	Designed for Enphase microinverters
Fortress eVault Max	Lithium Iron Phosphate (LiFePO4)	18.5 kWh	8,000 cycles @ 80% DoD	Compatible with various solar inverters
Generac PWRcell	Lithium Iron Phosphate (LiFePO4)	9 to 18 kWh (modular)	Varies	Integrated with Generac PWRcell inverter
LG Chem RESU 10H	Lithium Nickel Manganese Cobalt Oxide (NMC)	9.3 kWh	6,000+ cycles	Compatible with various solar inverters
Panasonic EverVolt	Lithium Nickel Cobalt Manganese Oxide (NCM)	11.4 to 17.1 kWh	6,000+ cycles	Can be paired with various inverters
Sonnen Eco 10	Lithium Iron Phosphate (LiFePO4)	10 kWh	10,000+ cycles	AC-coupled; compatible with various inverters
Tesla Powerwall 3	Lithium Iron Phosphate (LiFePO4)	13.5 kWh	4,000+ cycles	Integrated inverter

*Note: The "Cycle Life" values are approximate estimates

Why Is Solar Energy Storage Important?

As the electrical grid ages and extreme weather events increase, power outages are becoming more frequent. In wildfire-prone regions, utilities are implementing planned Public Safety Power Shutoffs (PSPS) to reduce fire risk—leaving many homes and businesses without electricity for hours or even days.

While gas-powered backup generators offer a short-term fix, they rely on fossil fuels, generate noise, and emit carbon. In contrast, solar energy storage systems are a clean, quiet, and increasingly cost-effective solution. These systems store surplus solar electricity for later use—providing solar power backup during grid outages and helping stabilize the broader grid by balancing supply and demand.

In high-solar penetration regions, excess solar energy during midday often leads to curtailment or wasted electricity. This challenge is visualized by the duck curve, which illustrates the mismatch between solar generation and consumer demand. Solar energy storage helps address this by storing unused power during low-demand periods and discharging it when demand spikes—enhancing overall grid efficiency and reducing waste.

Types Of Solar Energy Storage Systems

Installers should understand the different types of solar energy storage systems available—each suited to specific use cases based on application size, duration needs, and available space.

Electrical Storage

The most common form of solar energy storage today uses battery technology to store electricity. Popular battery chemistries include:

• Lead-acid batteries (e.g., sealed AGM): Affordable but lower cycle life.

• Lithium-ion batteries: High-efficiency and long lifespan. Two key chemistries:

  • Lithium Iron Phosphate (LFP) – Stable, long-lasting, and ideal for solar power storage.

  • Nickel Manganese Cobalt (NMC) – Higher energy density, common in compact systems.

These technologies dominate the residential and commercial solar energy storage market, offering flexible solar energy storage solutions for backup and peak shaving.

Chemical Energy Storage Systems

Less common but emerging, chemical energy storage stores power in molecular bonds rather than direct electricity. A key example is hydrogen energy storage, which uses electricity to produce hydrogen via electrolysis. The hydrogen can then be stored and used in fuel cells to generate electricity—suitable for long-duration solar energy storage options or remote/off-grid use cases.

Thermal Energy Storage

These energy storage systems use a material, such as water, molten salts, or sand, in an insulated tank to store heat. Then, this energy is either used to generate electricity or is used to provide heat. Thermal storage is useful for concentrated solar thermal power (CSP) plants that focus sunlight to heat a fluid.

A relatively widespread application is solar thermal water heaters that use solar collectors to heat water in a storage tank. The hot water can then be used as domestic hot water or to heat buildings through a heat exchanger or a radiant floor heating system. However, researchers at Lawrence Berkeley National Laboratory are investigating how to take this to the next level using next-generation materials and systems.

Determining The Best Type Of Solar Energy Storage

When selecting a solar energy storage system, it's important to consider factors such as power rating, usable storage capacity, roundtrip efficiency, warranties, cost, and battery lifespan. Lead-acid and lithium-ion are the two most commonly used battery types for storing solar energy, but solid state battery technology is advancing rapidly and will start being mass produced in the near future.

While lead-acid batteries are more affordable, they tend to have a shorter lifespan and warranty period. As lithium-ion battery prices continue to drop, they are becoming increasingly popular for residential and commercial solar applications due to their longer lifespan and better overall performance.

LFP (LiFePO4) Vs. NMC Solar Batteries

When it comes to solar energy storage systems, two main lithium-ion battery chemistries dominate the market: Lithium Iron Phosphate (LFP or LiFePO₄) and Nickel Manganese Cobalt (NMC). Both offer unique advantages, and understanding the differences is key when selecting the right solar energy storage solution for your clients.

Popular LPF and NMC Solar Energy Storage

NMC batteries are widely used for solar energy storage, and the Generac PWRcell, LG Chem RESU, Panasonic EverVolt, and Tesla Powerwall 2 are NMC batteries. However, the Enphase IQ, Fortress Power eVault, Sonnen Eco, and Tesla Powerwall 3 are LFP solar energy storage systems

Advantages of LiFePO4 Solar Energy Storage Systems

LiFePO4 batteries offer several advantages for solar energy storage systems, combining safety, longevity, stability, and environmental benefits.

• Safety: LiFePO4 batteries are known for their excellent safety profile. They are less prone to thermal runaway and are more stable at high temperatures than NMC solar energy storage batteries.

• Long Cycle Life: LiFePO4 batteries typically have a longer cycle life compared to NMC solar energy storage systems. They can withstand more charge and discharge cycles before experiencing significant degradation.

• Stability: LiFePO4 chemistry is inherently more stable, which contributes to a reduced risk of thermal runaway and enhances the overall safety of the solar storage system.

• High-Temperature Performance: LiFePO4 batteries perform well in high-temperature environments, making them suitable for applications where elevated temperatures may be a concern.

• Flat Discharge Curve: LiFePO4 batteries exhibit a relatively flat discharge curve, meaning they provide a consistent voltage output over a wide range of states of charge. This can be advantageous for certain applications.

• Environmental Impact: LiFePO4 batteries are considered more environmentally friendly than NMC solar energy storage as they contain fewer rare and toxic materials.
  

Advantages of NMC Solar Energy Storage

NMC batteries provide several benefits to solar energy storage systems, particularly where space, weight, and cost efficiency are essential.

• Energy Density: NMC batteries generally have a higher energy density than LiFePO4 batteries, meaning they can store more energy in a given volume or weight. This makes them suitable for applications where space or weight is a critical factor.

• Cost: NMC solar energy storage batteries can be more cost-effective to manufacture, making them a popular choice for various applications where cost considerations are paramount.

• Wider Voltage Range: NMC batteries often have a wider voltage range, providing flexibility in designing battery packs for specific voltage requirements.

• Application Flexibility: Due to their higher energy density, NMC batteries are commonly used in electric vehicles and applications where maximizing energy storage in a limited space is crucial.

Which is Better, NMC or LFP Solar Storage Systems?

Typically, LFP solar energy storage systems have a longer lifespan and are safer. In contrast, NMC batteries are usually a bit less expensive, have a higher energy density, and can withstand colder temperatures slightly better. However, NMC solar energy storage systems are not necessarily more cost-effective than LFP batteries because they can have a shorter lifespan.

AC Vs. DC-coupled Solar Energy Storage Systems

When selecting a solar energy storage system, it is also helpful to consider the inverter. Some solar energy storage batteries are AC coupled, so they have built-in battery inverters. Because AC-coupled solar systems do not require a hybrid inverter, they work with microinverters and string inverters.

If a DC-coupled solar energy battery is used, a hybrid inverter, such as the SolarEdge StorEdge, is required. AC-coupled batteries include models like the Enphase IQ, Generac PWRcell, Sonnen Eco, and Tesla Powerwall 2.

Considerations	AC-Coupled Solar Energy Storage	DC-Coupled Solar Batteries
Efficiency	May have slightly lower conversion efficiency due to extra energy conversion steps	May have lower energy conversion efficiency due to additional steps.
Flexibility	Highly flexible and scalable; ideal for retrofits	Limited flexibility in system design, especially in retrofitting.
Installation Ease	Simpler installation process, especially for retrofits.	Installation can be more complex, requiring coordination with PV array.
Battery Compatibility	Compatible with a wide range of solar energy storage batteries.	Compatible with specific battery technologies, usually lead-acid.
System Monitoring	Enhanced monitoring capabilities for both PV and battery.	Monitoring may be limited, depending on the system configuration.
System Expansion	Easier to expand the system with additional components.	Expansion may require more intricate planning and adjustments.
Battery Placement	Solar energy storage systems can be located at any distance from the PV array.	Batteries need to be located near the PV array for efficiency.
Cost	Generally more cost-effective for small to medium systems.	Cost may be higher due to additional hardware and complexity.
Compatibility with Inverters	Compatible with a wide range of inverters.	Requires inverters specifically designed for DC-coupled systems.

Different Types Of Solar Energy Storage Systems Suit Different Applications

Choosing the right solar energy storage system is essential for a successful project. While many options are available, some are better suited for specific applications or configurations. Understanding your project’s goals and budget is key to selecting the best solar energy storage solution. The GreenLancer team is here to assist with all types of solar energy systems.

Work with GreenLancer on your next project to take advantage of our extensive expertise in adding solar energy storage to many different PV projects. We can help with solar permitting, engineering stamps, and utility interconnection applications. Complete the form below to learn more.