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How Does Solar Battery Backup Work?

The number of residential solar installations with battery backup has steadily increased in recent years, helping to revolutionize the US electric grid. California and Florida homeowners can reduce their reliance on the grid, prepare for outages, and save money on energy costs by installing a battery system. But how does solar battery backup work?

How Solar Energy Is Stored in a Battery

A solar panel installation that doesn’t come with solar energy storage exports excess electricity back to the grid through a process called “net metering.” Likewise, these net-metered solar systems import electricity from the grid when your home needs more electricity than the amount your solar panels produce. Solar batteries reduce this grid dependence by storing excess energy for later use. 

Lithium-ion batteries are the most commonly used storage battery as they’re affordable, readily available, and require a smaller storage space. So how does solar battery backup work? Here’s a breakdown: 

  1. Harnessing Solar Power: The process begins when sunlight hits your solar panels, converting solar energy into electrical current.
     
  2. Battery Charging: The electricity produced by your solar panels will be used to power your home during the day. When your solar system produces surplus energy, it begins charging up your battery. How quickly your battery charges will depend on the amount of energy produced, how much your home uses, and the size of your home’s solar system.

  3. Energy Conversion: If your solar system is DC-coupled, the electricity enters the battery immediately and is stored as direct current energy. When your home requires this energy, the stored DC power is fed into an inverter, converted to AC power, and used as needed.

AC-coupled solar systems work differently, as the electricity stored in the battery is inverted three times before use:

  • First, DC electricity flows from the solar panels to an inverter, which converts it to AC electricity for immediate use.

  • Then, if the energy isn’t needed, it flows to another inverter that turns it back to DC energy for battery storage.

  • Finally, when power is required, the stored DC energy will flow through another inverter to become usable AC energy for your home. 

Aside from the benefit of being grid-independent, California homeowners can also enjoy exclusive rebates for installing solar energy storage systems, making it a worthy investment. 

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How Long Does a Solar Battery Backup Last?

Have you considered upgrading your solar energy systems with a backup battery? If so, you’re probably wondering: “How long does a solar battery backup last, and how often must it be replaced?” Here’s what you should know.

What to Expect with Solar Backup Batteries

The lifespan of home solar backup batteries is between 5 and 15 years, while solar panels have a life expectancy of around 25 to 30 years. Using this information to determine how long solar backup batteries last, you can expect to replace your solar batteries at least once or twice throughout the lifespan of your home’s solar system. You can break down a solar battery’s expected life into these two primary definitions: 

  • Useful Life: Solar batteries are at the end of their useful life when their storage capacity fails to meet about 60% of their normal capacity.
  • Warrantied Life: Your solar battery’s warranty refers to the specified length of time it’s guaranteed to perform at its peak condition. The model and brand you choose determine this information, and the guarantee period typically lasts up to 10 years. 

Factors Affecting the Lifespan of Solar Backup Batteries 

When answering the question, “How long does a solar battery backup last?” the following factors come into play: 

  • Solar Battery Usage Cycles: A cycle occurs when your solar battery completes a full charge and discharge. Generally, the more you cycle the battery, the shorter its lifespan.

  • Battery Type: Lithium-ion and lead-acid are the most common solar battery backups available on the market. While lead-acid is more affordable, lithium-ion solar batteries are more compact and have a longer lifespan.

  • Maintenance: Proper maintenance is crucial to lengthening the lifespan of solar batteries. Experts recommend following the manufacturer’s instructions for proper battery maintenance and investing in professional services to evaluate your system’s efficiency.

  • Temperature: Extremely cold or hot temperatures are not ideal for solar batteries. To maximize their lifespan, you should store them in a place unexposed to harsh elements. Fortunately, solar service providers advise California and Florida homeowners on the optimal location to store backup batteries.

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How Much Is a Solar Battery Backup?

California and Florida homeowners can expect the cost of solar batteries to range between $10,000 and $20,000, including installation costs. 

The price of a solar battery system largely depends on its kilowatt-hours (kWh) capacity, which usually ranges from $400 to $750/kWh. In general, home solar batteries store between 10 to 20kWh of electricity. If you invest in a 10kWh battery, you can expect to pay anywhere from $4,000 to $7,500. 

How much a solar battery backup sets you back might also depend on available incentives. When paired with full solar systems, California and Florida homeowners can benefit from tax credits and lower the overall cost.  

What’s the Purpose of a Battery Backup?

Solar batteries allow homeowners to store the excess energy generated by their solar systems. This stored energy can be utilized during power outages, after sunset, or be sold back to the grid for bill credits. Over time, it can help increase energy resiliency and reduce utility costs. 

These benefits make solar a smart investment, enabling the system to pay for itself no matter how much a solar backup battery costs initially.

Factors That Affect the Cost of a Solar Battery

How much is a solar battery backup system? We’ve discussed the general range, but certain factors determine the final cost. 

  • Energy Capacity: Solar batteries that can store more kWh are more expensive than units with less capacity.

  • Battery Chemistry: Lithium-iron phosphate (LFP) costs more than lead-acid batteries, as they tend to last longer and require less maintenance.

  • Depth of Discharge (DOD): The depth of discharge pertains to the amount of energy that can be withdrawn from the battery, relative to its total capacity. If a solar battery has 100% DOD, you can use its total storage capacity to power your home. The higher the DOD, the more expensive the solar battery will be.

  • Special Features: Batteries with inbuilt inverters, smart technologies, ancillary equipment, and other upgrades cost more.

  • Installation: Labor and installation costs add up to how much a solar battery backup is overall, especially if you purchased the storage system on its own.

  • Incentives: The 30% federal tax credit can lessen the overall cost of a solar system paired with batteries. California homeowners can also enjoy the SGIP incentive program for energy storage systems if the program’s criteria are met. 

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