Whole-Home Battery Backup Systems Frequently Asked Questions

Backup batteries operate on electricity and can function independently or as part of a home solar panel system. In the event of a power outage, the backup battery system will automatically activate, providing electricity for several hours, a day, or even longer.

Home battery backup systems have become increasingly popular thanks to their numerous benefits. One of the primary benefits is power continuity. During power outages or blackouts, a home battery backup system can keep essential appliances running, such as lights, refrigerators, and medical equipment. Additionally, a home battery backup system can help save money on electricity bills by storing excess energy from solar panels during the day and using it during peak hours when electricity prices are high. This saves money and has environmental benefits by reducing greenhouse gas emissions.

Moreover, a home battery backup system can provide energy independence, allowing homeowners to generate and store their energy, providing peace of mind, and reducing dependence on the grid. Installing a home battery backup system can also increase property value. It makes a home more attractive to potential buyers while improving energy efficiency, a desirable feature in today's market.

Lithium-ion batteries are the most common type of battery used in home systems. These batteries are energy-efficient, lightweight, and widely used in popular battery backup products such as Enphase, EP Cube, and Stackrack. On the other hand, lead-acid batteries have been in use for centuries and are commonly used in cars. They are cheaper than lithium- batteries but less efficient, making them better suited for small systems. Another type of battery, the flow battery, is less common in home systems but is mainly designed for commercial use. While it has promising technology, it may take some time before it becomes more widely used in residential battery backup systems.

Whole home battery backup systems can range in price from around $8,000 to $20,000, depending on various factors. The cost is impacted by the size of the home, the number of appliances that require backup power, and the battery capacity needed. Larger homes with more appliances will require additional batteries with higher capacities, increasing the cost of the system. The type of battery used can also impact the price, with lithium-ion batteries being more expensive than lead-acid batteries. The installation cost can also vary depending on the installation's complexity and the home's location. While the initial cost of a whole home battery backup system may seem high, it can provide long-term cost savings and peace of mind during power outages.

Once the initial installation is complete, a battery backup system requires minimal maintenance. Unlike a generator, there is no need to replenish a fuel source or perform regular maintenance.

The California Public Utilities Commission (CPUC) operates the Self-Generation Incentive Program (SGIP), which provides a rebate of up to $10,000 for homeowners who install battery storage systems. The SGIP rebate is given as a reimbursement after the installation is complete and covers both the equipment and installation costs. Even if the battery storage system is not paired with solar, it can still qualify for SGIP. However, it is beneficial to pair solar and battery storage in California. Depending on their utility, some Californians are eligible for a 15-20% SGIP rebate. In comparison, others qualify for rebates that cover 85% or even 100% of the cost of battery storage, allowing them to receive free battery storage through SGIP. Additionally, there is a 30% Federal tax incentive on the total system cost and rate benefits through Southern California Edison.

Learn more about SGIP here.

Learn more about Tax Credits here.

Learn more about SCE rate programs here.

Batteries typically have a lifespan of 15 to 18 years, but several factors can influence this. Lithium-ion batteries are usually used in home solar power systems because they have a longer lifespan than lead-acid batteries. The frequency of discharging a solar or backup battery system can also affect its lifespan, as more frequent discharges will result in a shorter lifespan. Additionally, extreme temperatures and severe weather conditions can reduce the longevity of your solar/battery storage. Therefore, it is essential to consider these factors when choosing a whole-home backup battery system and to properly maintain it to ensure it lasts as long as possible.

Capturing power from the grid and storing it for peak demand times or power outages is a little-known benefit that many homeowners are unaware of. This can be accomplished independently of solar panels using battery storage.

Determining the appropriate battery size for your energy needs involves evaluating your energy consumption over the past year and determining whether you can use excess solar power during periods of low solar generation if you already have a solar panel system. If you're not generating a lot of electricity or exporting much to the grid, a smaller battery may be appropriate. However, if you have excess solar generation and regularly import power from the grid, a larger battery may be beneficial. Matching the battery size to your energy usage patterns can help optimize its effectiveness.

A kilowatt hour (kWh) is a unit of measurement used to quantify how much energy an appliance consumes in an hour in thousand-watt increments. For example, running a 1,000 Watt microwave for a maximum of one hour consumes 1 kWh, as does running a 100 Watt light bulb for 10 hours. One Enphase battery can store up to 10.08 kWh of power, which means it could power a 1,000 Watt microwave for up to 10 hours or power multiple appliances, such as lights and a TV, for a shorter period. However, it's important to note that each Enphase battery outputs a maximum of 3.84 kW of energy at any time. So, it's crucial to ensure you don't continuously run more than 3.84 kW of appliances at once. Keep in mind this is for one 10kw battery. With more batteries installed comes greater storage and output capabilities.

Battery systems for solar storage or on their own are usually not set up exclusively for off-grid use. While they can store solar energy to power a home at night and provide backup power during outages, they may have limited capacity to support off-grid functionality for an extended period of solar production, which is suboptimal or insufficient. Additionally, some incentives for solar and storage solutions may only apply to grid-tied systems.

When it comes to backup power for your home, traditional generators may seem like a cheaper option upfront. However, the long-term maintenance and fuel costs often make a home battery a more cost-effective choice. For instance, fossil fuel generators require a constant supply of natural gas, diesel, or propane and regular maintenance to ensure their moving parts are in good working order. Service agreements for standby generators can be expensive. In contrast, a home battery requires no fuel or planned maintenance.

Although a home battery system, paired with solar panels, is an excellent solution for backup power during outages, it's essential to have realistic expectations about its capabilities. Whole-home backup batteries (that are not paired with solar) charge by pulling power from the grid and storing it. While it's possible to power your home for several days using a home battery, it's advisable not to depend on it for more than five consecutive days. Solar panels generate electricity during the day, which recharges the battery, and the battery then powers your home at night. However, without solar panels, the length of time the battery will last will depend on its size and energy usage. We recommend homeowners size their system to provide at least 12 hours of backup power. Still, it's crucial to remember that during storms or other situations that may hinder solar energy production, the battery may not be able to recharge as quickly. Therefore, it's essential to consider factors like weather and usage when determining the appropriate size and configuration of your home battery system.