Choose Your Backup Goal
What Should Your Battery Backup Do?
Essential Loads
Keep the most important things running during an outage, such as your refrigerator, lights, internet, medical equipment, and selected outlets. A smaller battery system can often handle these essential loads.
Whole-Home Backup
Power most or all of your home during an outage, including larger loads such as air conditioning, well pumps, electric appliances, and other household systems. This requires a larger battery system and careful load planning.
The right battery backup depends on what you want to keep running, how long you need backup power, and how much power those devices require.
UNDERSTAND THE BASICS
Battery Capacity and Power Output Are Different
Battery Capacity (kWh)
Capacity tells you how much energy the battery can store. A larger capacity generally means the battery can power your selected devices for a longer time.
Power Output (kW)
Power output tells you how much electricity the battery can deliver at one time. A battery may have plenty of stored energy but still be unable to run a large appliance if its power output is too low.
BUYING CONSIDERATIONS
Compare the features that affect how much power you can use, how long the battery can last, and how well it fits your home.
Usable Capacity
Continuous Power
Surge Power
Continuous power is how much electricity the battery can deliver at one time. It determines how many devices you can run together without exceeding the battery's output limit.
Surge power is the extra electricity some appliances need when they first start. Your battery must be able to handle these short startup demands as well as its normal running power.
Battery Life
Usable capacity is the amount of stored energy you can actually use. A battery's advertised capacity may be higher than the amount available for your home.
Battery life depends on the battery chemistry, how it is used, operating conditions, and how often it is cycled. Check the manufacturer's expected life and warranty before buying.
Installation
Permanently installed battery systems may require electrical work, transfer equipment, permits, and professional installation. Check local requirements before you buy.
Expandable Capacity
Expandable systems let you add battery capacity as your power needs grow. This can be useful if you want to start smaller and increase storage later.
How Battery Size Affects Runtime
A battery with enough stored energy may still be unable to run a large appliance if its power output is too low. Your actual runtime also depends on the devices you choose to run and how much electricity they use.
Power — Watts (W)
Watts tell you how much electricity a device uses at a given moment. A refrigerator, microwave, or air conditioner may require more power when it starts or when it is working harder.
Energy — Watt-Hours (Wh)
Watt-hours tell you how much energy a device uses over time. A device using 100 watts for 5 hours would use about 500 watt-hours of energy.
Kilowatt-hours are used to describe how much energy a battery can store. One kilowatt-hour equals 1,000 watt-hours. A larger usable capacity generally allows you to run your selected devices for longer.
Battery Capacity — kWh
UNDERSTAND THE NUMBERS
Runtime Depends on Both
HOW TO COMPARE
How to Compare Home Battery Options
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Step 3
How Much Energy Do You Need?
How Much Power Do You Need?
What Features Matter?
Start with usable capacity, measured in kilowatt-hours (kWh). This tells you how much energy the battery can store and deliver. A larger battery can provide more energy, but your actual runtime depends on what you are powering.
Check the battery's continuous and surge power ratings. Continuous power shows how much electricity it can deliver at once, while surge power handles the short startup demands of appliances such as refrigerators, pumps, and air conditioners.
Look beyond capacity and power ratings. Consider battery life, installation requirements, warranty, expandability, and whether the system can grow with your future power needs.
Can Solar Keep Your Battery Charged During an Outage?
A properly designed solar-and-battery system can recharge the battery during the day and use stored energy later. This can provide longer backup than relying on the battery alone, although cloudy weather and household electricity use can reduce how much energy is available.
Solar Makes Electricity
Solar panels produce electricity when sunlight is available. That electricity can power your home, charge a battery, or do both, depending on how the system is designed.
The Battery Stores Energy
A battery stores electricity for use when solar production is low or when you need more power than the panels are producing. This lets you use stored energy at night and during periods of limited sunlight.
During an outage, solar does not automatically keep a home powered. The inverter, battery, solar equipment, and home electrical system must be capable of operating together while the grid is unavailable.
Backup Depends on the Entire System
BATTERY + SOLAR
Solar Can Extend Backup Time
Solar panels can recharge a battery during an outage, but the system must be designed to operate when the grid is down. The amount of energy you can restore depends on your solar array, battery capacity, weather, and how much electricity your home is using.
What Might Your Battery Need to Run?
The right battery depends on what you want to keep running and for how long. These examples show how the same battery can provide very different results depending on the appliances and devices you choose.
Essential Loads
A smaller battery may be enough to keep important devices running during an outage. A refrigerator, lights, Wi-Fi equipment, and a few small appliances can often be prioritized without powering the entire home.
Larger Loads
Adding higher-power appliances such as a microwave, well pump, or air conditioner increases the power your system must deliver. These appliances may also require extra startup power.
Running most or all of your home requires a much larger system. The battery must have enough stored energy for the desired runtime and enough power output to handle the appliances operating at the same time.
Whole-Home Backup
PUT IT INTO PRACTICE
The goal is to match the battery to what you actually need.
Start by deciding which appliances and devices matter most, then use our calculator to estimate how long a battery can power them.
Which Type of Battery Backup Is Right for You?
A portable system may be all you need for a few essential devices, while a permanently installed system may make more sense if you want automatic backup for your home. Installation requirements, available power, storage capacity, and your intended use should all be considered before buying.
Portable power stations are designed to provide electricity where you need it without a permanent installation. They can be useful for selected appliances, electronics, RVs, and short-term backup needs.
Some battery systems allow additional batteries to be added as your power needs grow. This can provide a way to start with a smaller system and increase storage capacity later.
Permanently installed home battery systems are designed to work with your home's electrical system. They can provide backup for selected circuits or, with a properly sized system, much of the entire home.
SYSTEM TYPES
The system type matters as much as the battery size.
Battery backup systems range from portable power stations to permanently installed systems. The right choice depends on what you want to power, how long you need it to run, and how much of your home you want protected during an outage.
What Should You Know About Installation?
Battery backup systems are not all installed the same way. Portable systems may require little or no installation, while permanently installed systems must be properly connected to your home's electrical system.
Installation Requirements
Permanently installed systems may require electrical work, permits, transfer equipment, and professional installation. Requirements can vary depending on the system and where you live.
Safety Matters
Battery systems can store a large amount of energy. Follow the manufacturer's installation and operating instructions and use properly rated equipment. Never connect a battery or generator to household wiring in an unsafe or improper way.
The location of a battery system matters. Space, temperature, weather exposure, access, and required clearances can all affect installation. Follow the manufacturer's requirements for the specific system.
Installation Location
BEFORE YOU BUY
The battery is only part of the backup system.
The inverter, wiring, transfer equipment, installation, and operating environment all affect how safely and effectively the system works. Make sure the complete system is appropriate for your home before buying.
PUT IT TO THE TEST
Estimate Your Battery Runtime
Battery Runtime Calculator
Estimate how long a home battery can power the appliances and devices you choose.
How Long Will Your Battery Last?
Choose the appliances and devices you want to run and see how long a battery could power them during an outage.