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Solar Battery 101

Learn the basics about solar batteries and battery installation.

  • Solar batteries are used to store energy generated by solar panels
  • Lithium ion batteries are the most popular for home storage systems; lead acid batteries are the cheapest
  • Solar batteries can be stored indoors or outdoors as long as they do not face direct sunlight
  • 8-12 batteries may offer self sufficiency without relying much on grid electricity

What is a Solar Battery?

Solar batteries store energy generated by solar panels. They enable you to continue using appliances at night, at times with low sunlight, and during a power outage. Batteries also help reduce the risk of declining feed-in tariffs and rising electricity prices.

A solar battery gives you more alternatives for powering your home. With it, you can store excess electricity for periods when your solar panels are not producing enough.

You can run your home primarily on solar-generated energy if your battery and rooftop solar system are large enough. In addition, depending on the time of day and local electricity rates, utilizing electricity from your battery may be less expensive per kilowatt-hour than using electricity from the utility grid.

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If you do not have a solar battery, you may need to generate and consume electricity simultaneously.

Are Battery and Energy Storage Systems the Same Thing?

Batteries are a type of energy storage system. Their main purpose is to provide you with the energy you can utilize whenever you choose.

Generally, energy storage systems store electricity and discharge it when needed. Some energy storage systems can be charged with electricity from the grid or an energy generation source.

Solar batteries increase the value and quality of a solar system by storing solar-produced energy for less sunny hours and during power outages.

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Battery Installation

How to save on solar battery installations

How Much Space Will I Need for My Batteries?

The amount of space you need for your solar batteries depends on the size of your solar batteries. Solar batteries come in different sizes, including small, medium, and large. The size of a battery determines the battery price, capacity, and voltage.

The table below shows the various sizes of solar batteries, along with their voltage, capacity, and dimensions.

Solar battery Dimensions (inches)
12V 7Ah 5.94” x 2.55” x 3.74”
12V 10Ah 5.94” x 2.55” x 3.78”
12V 18Ah 5.94” x 3.95” x 3.78”
12V 23Ah 7.12” x 3.03” x 6.57”
12V 54Ah 7.12” x 3.03” x 6.57”
12V 100Ah 12.99”x 6.77”x 8.66”

Solar batteries can be stored indoors or outdoors as long as they do not face direct sunlight. Prolonged exposure to elements may cause the batteries to degrade quickly.

If you stay close to the ocean, or in an area prone to heavy rainfall, or a neighborhood with high humidity, or a city with near constant sunshine, consider installing your batteries indoors. The best indoor locations are the garage and basement.

Note: It's best to speak to a licensed and professional installer to know exactly how much space you need for your batteries.

Where Should Solar Batteries Be Installed?

Solar batteries can be installed indoors and outdoors, depending on the type. The best location for them is anywhere out of direct sunlight.

The National Fire Protection Association (NFPA), a non-profit organization committed to setting codes and standards to ensure fire safety, offers some guidelines that may prove useful when trying to figure out where to install your solar battery.

To establish minimum standards for mitigating any risks connected with energy storage, they established NFPA 855: Standard for the Installation of Stationary Energy Storage Systems.

NFPA 855 specifies various installation locations for various capacities of energy storage systems.

Systems between 1 kWh and 20 kWh are regarded as home systems; systems larger than 20 kWh must adhere to commercial installation standards. According to NFPA 855, you can securely install your solar battery in the following places if your system is 20 kWh or less:

  • a garage, either attached or detached
  • Outdoors or on an exterior wall, so far as it is three feet away from doors or windows
  • In a storage area, a utility closet, or another location

Irrespective of the location, if you place your storage system indoors in an unfinished room, you must make sure that the walls and ceiling are shielded by at least a 5/8 inch gypsum board (also known as drywall) for fire resistance.

You should also make sure that there is a barrier to protect your battery from accidental damage, which could result in a fire or explosion if you are installing it in an area that could be affected by a car.

Are Batteries a Critical Component for Clean Energy?

Battery storage technologies are crucial to accelerating the transition from fossil fuels to renewable energy. Battery storage systems are important for supplying clean energy and meeting electricity demands.

They allow energy from renewable sources, like solar and wind, to be kept and discharged when required. The stored energy may be used when renewable energy-generating equipment, like solar panels, do not produce adequate energy. Stored energy can also be used at night, during cloudy periods, and during power outages.

The aim is to promote the continued use of clean energy even during off-peak periods. If you use a solar system without solar batteries, you will need to use the grid’s power when your system stops generating electricity.

Note: A significant percentage of California's grid’s electricity is produced using fossil fuels. To avoid using dirty energy to power your home, consider using batteries to store the extra clean energy produced by your system.

Do Batteries Come With Warranties in California?

Yes. Solar batteries come with warranties in California. The warranty period is usually between 10 and 15 years. Some manufacturers also provide information about the lifespan of the battery, which is usually five to 25 years.

Do I Need to Update My Home Insurance?

It is advisable to inform your insurer that you want to install a battery system. Your system can then be added to the list of covered home appliances as an extra appliance. Your insurance payments should not be affected by installing battery storage.

Will I Need a Permit to Install a Solar Battery?

Yes. Most counties in California require you to obtain a permit before installing an energy or battery storage system. You should contact your county to learn about the process for obtaining a permit.

Will a Solar Battery Save Me Money?

Although solar batteries are a sizable upfront financial investment, they can help you save money on energy costs in the long run by storing excess energy when demand is low and discharging it in peak periods.

With the right system, you won't need to rely on electricity from the grid when your solar system is not generating energy.

Furthermore, California provides rebates incentives through the Self-Generation Incentive Program (SGIP) for homeowners that connect a solar battery to their solar system.

The SGIP battery rebate makes clean, dependable energy available to California residents by reducing the price of a solar battery by one-third. This helps you save on solar batteries in the state.

What Is the Difference Between Battery Backup and a Generator?

Battery storage and generators that run on diesel, propane, or gas are backup power sources. However, they operate differently. Unlike a standard generator, solar battery storage units do not rely on fossil fuel during a power outage. Instead, the battery is charged with electricity generated by your solar array (or electricity from the grid if you do not have a solar system).

This and the fact that they are noiseless make batteries better for the environment.

The electricity your battery stores can be used during a power outage. Although battery backup systems may cost more upfront, you will save more over time because you will not need to buy fuel. In addition, batteries are compact.

Furthermore, you can use a battery backup system to reduce energy costs if you have a time-of-use utility plan. Using the energy from your battery backup to power your home will save you from paying expensive electricity bills when demand is at its highest. You can use your electricity normally during off-peak hours but at a lower cost.

On the other hand, a generator is connected to the electrical system of your home and will turn on immediately when your electricity goes out for optimal convenience. In times of power outages, generators are powered by fuel, usually natural gas, liquid propane, or diesel.

Some generators have a “dual fuel” function, which allows them to use more than one fuel source. An advantage that generators have over batteries is that they power almost every appliance in your home. Most battery backup systems cannot power heavy appliances like your refrigerator unless the power runs out quickly.

What Are the Different Kinds of Batteries?

Battery types differ based on electrochemistry and technology. The most common types used with solar systems are lithium ion and lead acid.


They are the most popular home storage batteries. They are used in electric vehicles, consumer electronics, smartphones, laptops, and cameras. They are considered the most reliable battery type for solar systems.

This is because they have a long lifespan and are very compact and light. They also have high capacity and energy density and require low maintenance. Their disadvantages include high cost, inflammability, and intolerance to extreme temperatures, discharge, and overcharge.

Lead acid

This is the oldest battery technology and is considered the cheapest and most available solution for power storage. They have the shortest lifespan and capacity. However, they are great if you are looking for a battery storage option on a budget.

While affordable. Lead acid batteries may cost you more in the long run because you may have to replace them regularly.

Generally, lead acid batteries are safer than other battery chemistries because their active ingredients are not flammable. Also, they are recyclable and can work in extreme temperatures. Some lead acid batteries (flooded lead acid batteries) require regular maintenance.

Other types (sealed lead acid batteries) do not need much maintenance and are more suitable for power storage solutions because of their longer lifespan and higher capacity. The main downsides of lead acid battery technology include slow charging, weight, and low energy density.


This battery type is known for its cheap cost and resistance to extreme temperatures. They can be used for long periods without experiencing damage. They are mostly used for large-scale energy storage.

Nickel-Cadmium batteries do not need constant maintenance, but they need ventilation. As of 2023, Nickel-based battery technology is not a popular pick for solar energy storage. The downsides of Nickel-based batteries include lower charging efficiency, expensive chargers, low density, limited memory effect, and a hard-to-define charging state.


Flow batteries store energy in liquid electrolyte solutions, unlike other conventional rechargeable batteries, which store energy in solid electrode materials. The vanadium redox battery is the most popular type of flow battery.

Other varieties include iron-chromium, iron-zinc, and zinc-bromine chemistries. Flow batteries hold a considerable market share in on-grid and off-grid energy storage systems, including large-scale applications, despite their low energy capacity and charge/discharge rate.

Their advantages include a very long lifespan (up to 30 years), excellent scalability, quick response times, and a low fire danger due to the non-flammable electrolytes used.

How Many Batteries Will I Need?

The number of batteries you'll need will depend on the house’s energy requirements.

Homeowners typically take different approaches when designing a solar-plus-storage system. Generally, there are three broad strategies to optimize a battery system: cost savings, robustness, and self-sufficiency.

You need enough energy storage to maintain your home self-sufficient during peak electricity pricing hours to save the most money using solar batteries.

This will be around 2-3 standard lithium-ion batteries to prevent utilizing grid electricity during peak hours and when your solar panels are not generating electricity.

Importantly, this does not imply that you are self-sufficient and do not use the grid at all; rather, it implies that you are optimizing your solar panel installation and utilizing as much of your solar electricity as feasible.

Regarding creating a resilient solar battery system, most residential homes will be able to keep the lights on during most power outages with a single ordinary lithium-ion battery.

Regarding creating a self-sufficient solar battery system (or off-grid), self-sufficiency necessitates a large amount of battery storage, especially if you intend to use it for extended periods without sunlight (cloudy weather, nights, etc.). Consider eight to 12 ordinary lithium-ion batteries.

How Do Batteries Work With Solar?

When you install solar panels, you usually install a “grid-tied” net-metered system. This implies that if your solar panels produce more electricity than you use, you can export the excess to the grid, and vice versa. If you consume more electricity than your panels produce, you can draw directly from the grid.

Net metering allows you to run your electricity meter backward when putting excess energy onto the grid and forward when taking from the grid. Your utility company bills you on the net for the electricity you use.

Using a solar plus storage (battery) system, rather than transmitting any excess solar production to the grid, you may use it to charge your energy storage system first using a solar plus storage system. You can draw from your solar battery rather than the grid when you need electricity after the sun goes down.

When you pair a battery with your solar panel system, you can draw power from either the grid or your battery when fully charged. This has two important implications: batteries supply backup power and can assist you in avoiding expensive utility rates. The charge and discharge cycles of solar battery storage are managed by an energy management system based on real-time needs and availability.

What Are the Different Ways of Connecting Batteries to a Solar Array?

You may use two methods to combine solar energy and battery storage: DC coupling and AC coupling.

DC coupling: DC (or “Direct Current”) coupled systems are mostly used when installing solar and battery storage simultaneously. In this configuration, there is no conversion necessary because the solar electricity is supplied directly (in DC form) into the battery system.

One inverter is frequently shared by the battery and solar systems in DC coupled systems. Additionally, DC coupled systems make it simpler to make sure that your battery receives all of its power from solar sources (as opposed to utility electricity from the grid). This is key to be eligible for the federal tax credit.

AC coupling: AC (or “Alternating Current”) coupled systems consist of a separate solar array and battery system. There are two inverters needed for AC coupling: one for the solar array (to convert solar energy from DC to AC so that it can directly flow into the house) and one for the battery storage (to convert solar energy back to DC to charge the battery).

The electricity generated by your solar system often flows into your home. The battery is then used to store any extra electricity that is not needed by your home at that time.

If including solar batteries to an existing solar array, most systems use AC coupling to enable them to keep the existing solar inverter and wiring. A second inverter is added to the existing inverter. You should note that AC coupled systems make it difficult to ensure that your battery is solely charged by solar, which is a crucial requirement for eligibility for federal tax credits.

What Is a Smart Inverter and Do I Need One?

A smart inverter works like a normal inverter by converting direct current (DC) from solar panels to alternating current (AC) to be used in the house or workplace. They then go beyond this basic feature to provide grid support functions, like dynamic reactive and real power support, voltage and frequency ride-through, and ramp rate controls.

Smart inverters are an important, but underappreciated, component of the battery storage system. They can control when and how your batteries run. Every battery storage system needs an inverter, and it will be configured to operate according to your preferences and requirements.

Some batteries have a built-in smart inverter that allows the battery owner additional programming control over when and how to use their battery. Smart inverters can be designed via mobile apps and web portals to run when it makes the most sense, given physical, financial, or owner-preference signals, as opposed to regular inverters that are programmed to perform in a predictable, static fashion. Batteries can be configured with their smart inverter to take advantage of utility rate structures that make storage economically advantageous.

How Do I Select a Qualified Solar Battery Installer in California?

When choosing a qualified installer, you should ensure they have the following qualities:

If you find more than one installer that fits the above criteria and you want to narrow your options further, you should consider the following:

  1. Workmanship warranties: Most top installers have workmanship warranties. You should check it to know what is covered and the duration of the warranties. Knowing who to contact if something goes wrong with your battery is crucial. Your battery is backed by many warranties, ranging from manufacturer warranties for various components to workmanship warranties from your installer.

    The workmanship warranty relates to the job the installer does. In California, contractors provide warranties on work done for home and business owners for one to 10 years. Ask your installer what is covered by the warranty, if there are any exceptions, and whether you would be responsible for any costs if they had to come out and inspect or replace some equipment.

  2. The use of subcontractors: There are situations where installers rely on subcontractors to do some, or all, of your storage installation work. It is common practice in the industry. You should, however, observe the level (or lack) of transparency regarding who will install your system and their use of subcontractors. Ensure the installer is transparent in the process of using sub-contractors. If an installer uses subcontractors, ask:

  • Why subcontractors will be used,
  • How much work will be subcontracted,
  • For information about the subcontractors,
  • The level of control or oversight the company has over the subcontractors, and
  • Who will guarantee the quality of the installation.
  1. Expertise: Find out how the installer intends to tailor their system to your needs. Every installation is different, hence, it is crucial to work with an installer that has experience creating energy storage systems specifically to meet the demands of their clients.

Be mindful of how installers respond to your inquiries about why they are recommending a particular battery over a smaller or larger system. The best installers will work with you to comprehend your needs and how storage fits into your total energy plans.

What Should Be Included in My Battery Backup Proposal?

You should have the following information in your battery proposal:

  • The total cost of the battery storage system, installation, and any additional equipment
  • Information about the battery and the additional equipment:
  • Battery size (kW and kWh)
  • Battery model and manufacturer
  • Battery management system (if used)
  • Inverter model and manufacturer (if different from the battery)
  • Critical load sub-panel size and cost
  • Payment milestones
  • All warranties (battery, inverter, installer workmanship)
  • Details of additional work needed (electrical work, inverter swap, etc.)
  • Pricing guarantee for all equipment
  • Installer’s details (office location, point of contact, contact information).
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