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A home battery backup system stores electricity — from the grid during cheap off-peak hours, from solar panels, or both — and delivers it to your home's circuits when the grid goes down. A transfer switch or smart panel senses the outage and shifts your home to battery power, often fast enough that you barely notice the lights blink.
This guide answers the questions people actually ask before buying: what it costs, how big a battery you need, how long it lasts, whether it's worth it, and how it compares to a generator — in plain, rules-of-thumb terms.
Three things happen in every system:
The inverter is the heart of the setup. If you're building or matching one, see our solar inverters and the inverter buyer's checklist.
Cost varies enormously with how much of your home you want to back up and who installs it. As a rough map:
The number that actually matters is cost per usable kWh, and DIY-friendly LiFePO4 gear lowers it substantially versus a fully installed brand-name system. Building the bank from modular server rack batteries or solar batteries is how many homeowners bring the price down.
Start from your daily use. Most homes run 20–40 kWh per day, but during an outage you only back up what you choose. A simple way to size it:
Battery size (kWh) ≈ loads you'll run (kW) × hours of backup you want
For the underlying runtime math — usable kWh, depth of discharge, and how long a given bank lasts — see our runtime & cost guide. Complete, voltage-matched systems are easiest to size from a solar panel kit.
You do not need solar to have a home battery. A battery-only system charges from the grid — great for outage protection and for shifting usage to cheaper off-peak hours. The trade-off: during a long outage it's a fixed reserve, so once it's empty it waits for the grid to return.
Add solar and the battery recharges every sunny day, which is what makes multi-day and true off-grid resilience possible. Both approaches are valid; it comes down to whether you want a reserve or a self-refilling system.
A battery is silent, emission-free, needs no fuel on hand, and switches over instantly. A generator runs indefinitely as long as you have fuel, which suits very long outages, but it's noisier and needs fuel storage and maintenance. Many resilient homes actually pair the two: a battery for instant, quiet, everyday backup, and a generator for worst-case multi-day events.
Are home battery backups worth it?
They're worth it if you value instant, silent, fuel-free backup, have frequent outages, or have time-of-use rates you can arbitrage. If you only lose power once a year for an hour, the math is harder to justify.
How much does a whole-home battery backup cost?
Widely from about $10,000 to $50,000+ installed for a full whole-home system; far less for an essentials-only or DIY LiFePO4 setup. Compare on cost per usable kWh.
How big of a battery bank do you need to run a house?
Roughly 10–15 kWh for essentials over a day; 20–50+ kWh to carry heavy loads for multiple days. Size it as loads (kW) × hours of backup wanted.
How long will a 15 kWh (or 20 kWh) battery power a house?
A 15 kWh bank runs a ~500W essentials load for a day or more, or a few hours under heavy whole-home draw. Divide usable kWh by your load in kW to estimate hours.
Can I have a whole house battery backup without solar panels?
Yes. A standalone battery charges from the grid and kicks in automatically during an outage — solar just adds daily recharging.
Which is better, a battery or a generator?
Battery for quiet, instant, everyday backup; generator for indefinite runtime in very long outages. Pairing both gives the most resilience.
What is the cheapest way to back up my home?
An essentials-only setup built from modular LiFePO4 batteries and a right-sized inverter, backing up only the circuits you truly need, is usually the lowest-cost entry point.
This article is general information and uses rounded rules-of-thumb and industry cost ranges, not electrical, financial, or professional advice. Actual cost, sizing, and runtime depend on your home, loads, rates, and equipment. Whole-home and grid-interconnected systems must be installed by a licensed electrician per the manufacturer's manual and local codes.