Home battery backup: how it works, what it costs and what it can run

Power cuts are getting longer in parts of the US. The Energy Information Administration found that customers went an average of about 11 hours without power in 2024, the most in a decade, with hurricanes accounting for most of it. That’s an average: some households lost power for days, many for a few minutes.

A home battery is one way to ride that out quietly, without a generator’s fuel and noise. It’s also expensive, so it pays to understand what you’re buying before you get quotes.

How a home battery keeps the power on

During normal operation, the battery sits alongside your electrical panel, charging from the grid or from solar panels. When the grid fails, a device called a gateway or transfer switch disconnects your home from the grid and the battery takes over. That disconnection is essential: it stops your battery feeding power into the street, where a line worker might be repairing cables.

The switch takes a fraction of a second with most modern systems, fast enough that clocks and Wi-Fi routers usually don’t reset.

What the battery then powers depends on how it’s wired:

• Partial-home (critical loads) setup. The installer moves your essential circuits, such as the fridge, lights, outlets and internet, to a separate subpanel. Only those circuits get backup.
• Whole-home setup. The battery backs up the main panel, so everything in the house can run, up to the battery’s power limit. Bigger appliances may need load management so they don’t all start at once.

Our guide to whole-home or essentials-only backup goes into this choice in detail.

Three ways to get battery backup

Option	Typical size	Output	Installation	Rough cost
Portable power station	1 to 2 kWh	1.5 to 2.5 kW	None; plug appliances in	About $500 to $1,500
Expandable home power station	4 to 12+ kWh	4 to 7 kW, 120/240 V	Transfer switch or inlet by an electrician	Several thousand dollars and up
Installed home battery	5 to 15 kWh per unit	About 4 to 11.5 kW per unit	Fully installed and permitted	About $13,000 for a 13.5 kWh unit

Portable power stations are the simplest. You run extension cords to the fridge and router during an outage. Our guide to how long a power station runs a fridge shows what 1 or 2 kWh gets you.

Expandable home power stations, such as EcoFlow’s DELTA Pro 3 (4,096 Wh, expandable to 12 kWh per unit) or Jackery’s Explorer 5000 Plus, sit between the two. They’re portable in principle, but with a transfer switch they can power home circuits, including 240 V appliances.

Installed home batteries are permanent systems. Common examples are the Tesla Powerwall 3 (13.5 kWh, 11.5 kW continuous), the Enphase IQ Battery 5P (5 kWh and 3.84 kW per unit, usually installed in multiples) and the FranklinWH aPower 2 (15 kWh, 10 kW). They’re installed by certified installers, need a permit, and integrate with solar panels and utility programs.

How much battery do you need?

Think in two numbers. Power (kW) is how much the battery can supply at once, which decides what can run together. Energy (kWh) is how much it stores, which decides how long it lasts.

For energy, list what you want to keep running and estimate daily use:

Essential	Typical use per day
Fridge-freezer	about 1 to 2 kWh
Chest freezer	about 0.5 to 1 kWh
Router and modem	about 0.3 to 0.5 kWh
LED lights in a few rooms	about 0.3 kWh
Phones and a laptop	about 0.2 to 0.3 kWh
CPAP machine	about 0.3 to 0.5 kWh
Gas furnace blower (winter)	about 1 to 3 kWh

A typical set of essentials comes to roughly 3 to 7 kWh a day. So a single 13.5 kWh battery, starting full, covers essentials for about two to three days with no solar. Compare that with a whole home: the average American household uses roughly 10,000 kWh a year, about 28 kWh a day, which would drain the same battery in half a day. That gap is why most people back up essentials, not everything.

For power, add up the running watts of everything that might run at once, then check the biggest starting surge. Well pumps, sump pumps and air conditioners are the usual surge problems.

What it costs in 2026

In the US, EnergySage puts a typical installed Tesla Powerwall 3 at about $13,473 before incentives, or $998 per kWh, which it says is below the average battery on its marketplace. Across brands, installed prices run from roughly $700 to $1,300 per kWh of usable capacity, depending on the brand, the installer and how much electrical work your home needs.

The big change for 2026 is the federal tax credit. The 30% residential clean energy credit, which covered batteries, ended under the One Big Beautiful Bill Act. Most sources read it as applying to systems placed in service by 31 December 2025, so a battery installed in 2026 doesn’t qualify. State rebates and utility programs still exist in some places, and some utilities pay battery owners to share stored power during peak demand.

In the UK, the government publishes the price of every MCS-certified battery installation. For April 2025 to March 2026, the median was:

Battery size	Median installed price per kWh
Under 6 kWh	£1,300
6 to 11 kWh	£890
11 kWh or more	£630

Installed batteries are zero-rated for VAT until 31 March 2027, including standalone batteries added to a home without solar. Our guide to solar battery storage costs breaks these numbers down further.

Battery or generator?

A standby generator running on natural gas or propane can keep a whole house going for as long as the fuel lasts, which a battery can’t match in a long outage. Generators need servicing, make noise and run on fuel, and they take several seconds to start, so your power does drop briefly.

A battery is silent, needs little maintenance, switches over almost instantly and can earn its keep day to day through time-of-use savings or utility programs. Its weakness is endurance: once it’s empty, it needs the grid or solar panels to recharge.

Some households pair the two: a battery for instant, quiet backup and a small generator to recharge it in a long outage.

Is it worth it?

As pure insurance, a home battery is expensive, and the honest answer for a home with one or two short outages a year is often no. A portable power station covers the fridge and Wi-Fi for a fraction of the cost.

It makes more sense if any of these apply:

• someone in the home relies on medical equipment,
• you work from home and can’t afford to lose power,
• your area has long storm outages,
• you’re on a time-of-use tariff or have access to a utility battery program,
• you have, or plan to add, solar panels.

If you don’t have solar, read our guide to battery backup without solar. It works, and the case for it is different. If you do, see how solar battery backup keeps your panels working in a power cut. And if you’re still deciding what level of backup you need, start with battery backup for power outages.