Why battery backup?
Benefits of home batteries
Batteries at Sunrun
A battery is a rechargeable storage device that holds electricity, allowing you to power essential devices or even an entire home. For homes with solar panels, a battery lets you store excess energy generated by the sun to use later, such as at night or during a power outage.
(Brief) History of Batteries at Sunrun |
2016 | YEAR | 2019 | 2023 | 2024 | 2025 | Future |
Battery sales | Powerwall sales began | Distributed Power Plants introduced | Solar Billing Plan introduced | New export feature introduced | Began optimizing Powerwall in select markets | 10G of distributed power |
Note: Batteries at Sunrun refer to lithium-ion home batteries.
Sunrun offers premium batteries, including:
Battery Equipment Details |
Hybrid Batteries
A hybrid battery is a battery that includes a 'solar assembly' component or a solar inverter. In most situations, this means the customer doesn't need a third-party inverter installed as the battery will also perform the functionality of an inverter.
AC vs. DC Batteries
AC-coupled batteries connect to your home's electric panel (the AC side, after the energy has already been converted from DC to AC). They can work with existing systems and can charge from both solar and the grid.
DC-coupled batteries connect directly to the DC output of the solar panels. They can only be installed with new solar installations and are limited in their ability to charge directly from the grid.
Battery Dimensions
H: Appx 35-45 inches
W: Appx 30 inches
D: Appx 6-8 inches
It is smaller than a kitchen appliance but larger than a customer's electric panel. You can think of it as about the size of a large flat-screen TV or a slim mini-fridge. See specific battery sizes on the specific battery product pages.
Battery Communication Devices
The installation will include a battery communication device designed to automatically tell the solar and battery system when to switch from interacting with the grid to backup mode, in which the home disconnects from the grid and becomes its own microgrid.
Learn more about Battery Communication Devices |
Many batteries also include another form of communication device: Current Transformers (CTs). CTs are installed with batteries that monitor and measure the electrical current flowing in a circuit or wire without physically touching the wire.
Learn more about Current Transformers (CTs) |
Why do customers get batteries?
Customers install batteries for three primary reasons: resilience, self-consumption, and to prepare for future energy needs.
1 | Backup | A battery provides uninterrupted power during a grid outage, keeping essential appliances and lights on. Without a battery, solar panels automatically shut down during a blackout to protect utility workers. |
2 | Self-Consumption | In areas where utilities don't pay well for excess solar energy sent back to the grid, a battery allows you to store that energy for your own use. This helps you maximize savings, especially if you are on a Time-of-Use (TOU) rate plan, by using your stored solar energy instead of expensive grid power during peak hours. |
3 | The Future | Many people are forward-thinking and want to reduce their dependence on the grid and fossil fuels. A battery is a key component of a comprehensive energy strategy for long-term energy independence and environmental sustainability. |
Batteries are not designed to back up lifesaving equipment.
Battery Benefit Details |
Backup | |
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Energy resilience | Battery backup systems provide a source of electricity during power outages. This is particularly valuable in regions prone to storms, blackouts, or unreliable grid power. Homeowners can maintain essential appliances and lighting even when the grid is down, enhancing their comfort and safety. Customers who have experienced outages and express how challenging outages have been or how frequently they have happened in the past are more likely to install a battery. Across the country, power outages from severe weather have doubled over the past two decades. Many people are aware of and concerned about worsening outages. Even if customers haven't experienced many outages historically, many want to be prepared and provide reliability and security to their families and homes. Some customers have specific appliances or circuits that they prefer to stay powered during an outage. |
Emergency Preparedness | Battery backup systems provide peace of mind during emergencies. They ensure that critical appliances like refrigerators, lights, internet, and communication equipment remain operational, improving a household's resilience in times of crisis. |
Self-consumption | |
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Solar power optimization | Battery storage systems can complement residential solar panel installations. Excess energy generated by solar panels during the day can be stored in the battery and used during the evening or on cloudy days, increasing the overall self-sufficiency of the solar system. |
Time-of-use savings | Many utilities charge higher rates during peak usage times; batteries allow customers to store excess power at home instead of sending it all back to the grid. They help homeowners save money by storing excess electricity during off-peak hours and using it when rates are higher during peak times. They also enable homeowners to shift their grid energy usage to times when electricity is more affordable. |
Energy independence | Battery backups can reduce a homeowner's dependence on the grid or the need for fossil fuel generators. This can be appealing for those looking to minimize their carbon footprint or reduce reliance on traditional energy sources. |
Grid Support |
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In some cases, homeowners with battery backup systems can participate in grid support programs. They can sell excess stored energy back to the grid during peak demand periods, potentially earning compensation or credits from utility companies. Learn more on the Battery Discharge Profile page. |
How Does Battery Backup Work?
A battery works with your solar panels by storing surplus electricity. When your panels produce more energy than your home is using, the excess is directed to the battery. When solar production is low or during an outage, the battery powers your home.
During the day: Panels produce energy. Any energy not used by the home is stored in the battery. Once the battery is full, any remaining energy can be sent to the grid.
During an outage: The battery's inverter automatically disconnects your home from the grid within seconds and begins to send power to your home's backed-up circuits.
Recharging: The battery recharges from the solar panels when the sun is out, which can provide backup power for multi-day outages.
Battery Backup Details |
Daytime Production | |
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When the sun is up, panels produce energy. With a battery, energy above what the home consumes is stored for later use. Once the battery is full, standard net metering resumes. |
Power Outage | |
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When there is a power outage, the battery automatically takes over and sends power to the backed-up circuits within seconds. This continues until power is restored or the battery runs out of energy. How long the battery lasts depends on how much energy is consumed during the outage. |
Recharges from the Sun |
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Typically, the battery supply will be low in the morning due to energy consumption throughout the evening when the solar panels aren’t producing energy. The battery refills when the sun is out. This can provide backup power for multiple-day outages. |
Battery Functionality
Customers can use batteries daily when needed or on rare occasions if they have a more reliable electric grid and a utility with full net metering.
With premium batteries like the Tesla Powerwall 3, Franklin, or Lunar Battery, many customers can back up their entire electric panel (typically if less than 35 breakers and the largest load ≤ 60/60/50A, respectively).
Battery Discharging Details |
Batteries can be recharged hundreds of times before their capacity significantly diminishes, which makes them cost-effective over their lifespan.
Batteries have a relatively low self-discharge rate, meaning they can hold their charge for a long time when their stored energy is not needed (backup-only markets).
Battery Backup Details |
With the Tesla Powerwall 3, Franklin, or Lunar Battery, many customers can back up their entire electric panel (typically if less than 35 breakers and the largest load ≤ 60/60/50A, respectively).
Customers can get multiple Tesla or Franklin batteries to back up larger loads (more power capacity) for a longer time (more energy capacity).
In our ONE Sales Offer Experience presentation tool, the choice in the number of batteries is displayed as Essential backup (1), Extended (2), or Plus (3+) backup.
Essential Backup | 1 battery | Essential home backups balance essential power provision with cost efficiency.* *In CA or HI, this option may not be available depending on the system's production. |
Extended Backup | 2 batteries | Backup Extended or Plus setups offer uninterrupted comfort and whole-home backup, with additional capacity and the ability to back up larger loads. |
Plus | 3+ batteries | Backup Extended or Plus setups offer uninterrupted comfort and whole-home backup, with additional capacity and the ability to back up larger loads. |
If customers do not have a backup battery with their solar panels, they will not have power during an outage. Learn more about whole-home versus partial-home backup on the Understanding the Backup Load Policy page.
Backup Expectation Details |
A battery is designed to offer approximately 8 to 12 hours of backup power to essential loads, but understanding how long they can power different devices in the home is crucial for informed decision-making.
With the appropriate battery capacity, customers can enjoy uninterrupted power critical loads during grid outages and effectively manage energy usage.
Understanding how much power (Watts (W)) different electrical loads use is essential to setting proper backup duration expectations. Learn more about Power and Energy, Electric Panels, circuits, breakers, and electric loads.
For example:
Small loads, lights, and electronics tend to be more efficient and can run longer using less energy.
Large loads that generate heat, require a motor, or are heavy loads will draw more power and drain a battery much faster.
Reference table:
Time | Energy used | |
|---|---|---|
Refrigerator | 24 hrs | 2 kWh |
Wifi | 24 hrs | 0.006 kWh |
5 LED 40W bulbs | 2.5 hrs | 0.5 kWh |
50” LED TV | 5 hrs | 0.75 kWh |
Laptop | 6 hrs | 0.5 kWh |
Water heater | 1-2 hrs | 4-8 kWh |
Pool pump | 4 hrs | 7-8 kWh |
Battery Installation Requirements
The installation requirements for a battery system can vary depending on several factors, including the type and size of the battery, local building codes, and safety regulations. The Installation timeframe depends on factors like system size and configuration, but typically takes one to two days.
Battery Installation Details |
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Battery location generally depends on where you live in the country. Typically, those on the West Coast with low-temperature fluctuations will install batteries outdoors, and customers in the Northeast will install batteries indoors to avoid weather affecting the battery's performance.
Location | Batteries should be installed in a well-ventilated, temperature-controlled space to ensure optimal performance and safety. The preference for indoor or outdoor installations varies by market. Common indoor locations include garages or utility rooms. |
Clearances | The chosen location should also be accessible for maintenance and emergency shutdown, which requires safety clearances. Adequate clearances around the battery are essential to facilitate maintenance, cooling, and emergency access. Follow the manufacturer's guidelines and local regulations regarding the minimum required clearances. |
Electrical Wiring | Battery systems must be connected to the electrical panel following the appropriate electrical codes. Proper wiring and grounding are critical for safety and functionality. |
Jurisdiction and Local Regulations | Many areas have specific rules for energy storage systems, which must be adhered to in the solar design to pass inspections. The specific location will be confirmed with the customer at the final design or CAP. |
Installation Complexity |
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Battery installation can vary in complexity based on the customer's current electrical situation and whether the battery is backing up their essentials, backing up their entire electric panel, or not providing backup at all. If loads need to be relocated, the installation is more complex. |
Home Disqualifications |
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Unless your utility company has explicit rules preventing you from installing a battery, there is no reason why a customer would not be able to sign up to install a battery with their solar panels. Factors like limited space, budget constraints, or the age of your existing electrical system could impact your home's current ability to add a battery. Low electrical consumption may limit a customer's ability to install two batteries. Work on the electric panel may be required to make a battery viable for a home. More information on home electrical upgrades can be found here. |
What would disqualify my home from getting a battery?
Battery Monitoring
Sunrun offers battery monitoring through the Sunrun Customer App.
Tesla Powerwall offers additional monitoring and features through the Tesla app for customers to customize their batteries to provide the most value. You can check the state of charge, energy consumption, and other important metrics in real-time.
Battery Billing
Customers adding a battery to their solar system will do so by selecting the Protection or the Ultimate Control bundles in the sales presentation in ONE. The customer will have the same product and payment method for their solar system and batteries, and the batteries will be included in their solar Agreement.
Adding a battery will impact the customer's utility bill differently depending on their utility rate structure.
Sunrun Billing Details |
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A customer can choose to pay for their battery and solar system outright, or the cost of adding a battery can be factored into a customer's monthly solar payments.
The cost of a battery varies based on the manufacturer, the scope of the installation, available market incentives, and many other factors.
Utility Billing Details |
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Time of Use: If a customer is on a Time-Of-Use rate schedule, a battery can reduce electricity bills by allowing you to use stored solar energy during peak rate times.
Solar Billing Plan: Batteries enhance energy savings by allowing customers to maximize their self-consumption of the energy they produce and reducing their reliance on the grid.
Other markets: If a customer is not in a Time-Of-Use market, the battery will not provide additional savings but resilience and peace of mind.
Batteries vs. Generators
Batteries are a more sustainable and convenient alternative to traditional generators. If a customer already has a generator, it is best practice to determine its age and use.
We cannot have a battery and generator powering the same inputs, so depending on how that generator is used will determine if installing a battery is feasible and makes sense for the customer.
Battery vs. Generator Details |
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No 'refueling' | The battery recharges when the sun is out, even on a cloudy day. This can provide power for multiple-day outages, turning a customer's home into their personal power plant. This kind of energy security is unique to solar systems with batteries, as generators still require fuel to maintain power during an outage. |
Cleaner fuel source | Batteries are electric-powered, whereas generators use gasoline or diesel as fuel. When paired with solar, batteries utilize a clean energy ecosystem to create more energy independence with less emissions. |
Quieter when in use | Batteries are quieter than generators because they don't involve combustion. Generators produce noise due to the burning of fuel, whereas batteries, on the other hand, store energy electrically and release it without the need for combustion, resulting in a much quieter operation. |
Automatic 'ON' | Unlike a generator, batteries don’t need to be switched on and don't require additional fuel. They activate as soon as a power loss occurs. Additionally, they automatically cycle and discharge energy. There is no action required for this. |
Installing a Generator Post-Solar |
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If a customer wants to install a generator post-solar, they can do that, but Sunrun does not provide generator installation services. They will need to contact an electrician to discuss installing a generator, keeping the following in mind:
The generator must be kept electrically separate from the solar equipment for safety and to prevent voiding their warranties and Performance Guarantee.
Customer Engagement: Confirm the customer's email address and email them from no-reply@sunrun.com using the appropriate “Equipment: Generator information” email template.
If a Lease/PPA customer's system will be shut down for more than a week, we will need to create a case and have a team lead reach out to the monitoring team to block system alerts during the installation period.
Want to Dig Deeper?
Battery Programming
Optimize your battery for peak performance
Learn about your battery mode choices and find the one that fits your lifestyle
Time-based
Self-power
Back-up only
Battery loads explained
Find the right battery solution for your home
Battery FAQ
Yes, batteries contain outlets, typically protected under a cover. Customers can plug their devices directly into the battery.
In certain markets, plugging essential appliances into your battery with extension cords is the preferred installation and backup method.
The lifespan of a battery varies based on its type and usage. On average, most solar batteries last around 10 to 15 years. You typically need to replace it at least once during the lifespan of your solar system.
How deeply a battery is regularly discharged affects its lifespan. Shallower discharges can prolong battery life compared to deeper discharges.
Extreme temperatures, both high and low, can significantly impact battery life; Sunrun takes this into account with installation location.
Batteries typically require minimal maintenance.
There is no work required to turn the battery 'on.' They automatically kick on in the case of an outage, providing a home with uninterrupted backup power.
Periodic checks, firmware updates, and ensuring proper ventilation are usually sufficient. Manufacturers provide guidelines for maintenance.
All batteries we install at Sunrun have a 10-year manufacturer's product warranty. They also guarantee a percentage of the battery's usable capacity at year 10, ranging from 60% to 70% of the original capacity.
If a customer signs up for a Sunrun-owned product, we will cover the battery for the entire length of the customer Agreement.
Learn more about the specific battery warranties on the specific product pages.
Expansion options depend on the battery and inverter setup.
Some systems allow for easy scalability, while others may require more complex modifications. Retrofit battery options are something Sunrun is actively pursuing; learn more about retrofitting batteries here.
Batteries can have a positive environmental impact by storing excess solar energy and reducing the need for electricity from the grid. This can lower carbon emissions and dependence on fossil fuels.
However, to prevent environmental harm, it's essential to dispose of old batteries properly. Many manufacturers have recycling programs.
At Sunrun, as we continue to grow and deploy systems, we are primarily responsible for managing the outcome of our hardware. We integrate product end-of-life processes in our environmental management system with the goal of decommissioning, redeploying, reselling, or recycling our used system equipment.
Solar batteries are designed with safety in mind. They include features like thermal management systems and protective enclosures to prevent overheating or accidents.
Proper installation and maintenance also contribute to their safety- which is why customers benefit from having Sunrun, the most experienced battery installer nationally.