Battery Backup Sump Pumps Worth Buying Before the Next Storm

Sump pumps fail when you need them most: in a storm, when the power's out. Our picks for the best battery backup sump pumps and combination systems from Wayne, Basement Watchdog and Zoeller.

By Tyler RamirezUpdated October 29, 2026How we pick products

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A sump pump is the last line of defense against a flooded basement, and it’s most likely to fail at the worst time. Heavy storms knock out power, and without power, a regular sump pump stops. A battery backup sump pump takes over automatically when the main pump loses power, fails or can’t keep up.

There are two ways to get one:

• Backup-only systems add a battery-powered pump next to the main pump you already have.
• Combination systems include a new primary pump and a backup pump, preassembled.

Compare at a glance

Flow ratings and features are from Bob Vila's guide and manufacturer specs. GPH means gallons per hour, and "at 10 ft" is the flow when pushing water 10 feet up. Batteries are sold separately for every pick; most use a deep-cycle marine battery. Prices change often, so check current listings.

How we chose these

We compared systems using Bob Vila’s guide and manufacturer specs, focusing on:

• Backup pumping capacity
• Combination vs backup-only design
• Alarms and remote alerts
• Build materials
• Ease of installation

We haven’t tested these ourselves. Read more about how we pick products.

1. Wayne BGSP50 Guardian: Best overall

Best for: Homeowners replacing an old pump who want primary and backup protection in one system.

Bob Vila named the Guardian the best battery backup sump pump overall. It pairs a strong primary pump with a battery backup, built from cast iron and aluminum. Its standout feature is smartphone alerts when the backup kicks in, so you’ll know there’s a problem even when you’re away.

What bugs us: The battery is sold separately.

Skip it if: your current primary pump is new and working well. A backup-only system is cheaper.

2. Basement Watchdog CITS-50: Runner-up combo

Best for: People who want a reliable combo without app features.

Basement Watchdog is one of the best-known names in backup pumps. The CITS-50 combines a cast iron and aluminum primary pump with a battery backup and sounds a loud alarm when the power goes out.

What bugs us: No WiFi, so you won’t get alerts away from home, and the battery is extra.

Skip it if: you travel often and want phone alerts.

3. Zoeller Aquanot 508: Easiest to install

Best for: DIYers who want a simpler installation.

Zoeller is a brand many plumbers trust. The Aquanot 508 arrives fully assembled with both pumps, and it has a light and audible warning.

What bugs us: The battery is sold separately, and depending on your pit and plumbing, you may still want a professional to install it.

Skip it if: you need the highest flow. The Wayne moves more water.

4. Basement Watchdog BWE: Best budget add-on

Best for: People with a good primary pump who want affordable backup protection.

The BWE installs alongside your existing pump and takes over when the power goes out. Its thermoplastic housing resists corrosion.

What bugs us: Its 1,000 GPH backup flow is lower than the others, which may not keep up in a basement that takes on a lot of water. The battery is extra.

Skip it if: your pump runs constantly during storms.

5. Basement Watchdog BWSP: Best smart backup

Best for: Anyone who wants to monitor their backup from a phone.

This backup-only system watches the water level and battery charge and sends alerts to an app, along with an audible alarm. It moves 1,730 GPH at 10 feet.

What bugs us: The battery is sold separately.

Skip it if: you don’t want another app.

What to look for

Enough backup flow

Backup pumps move less water than primary pumps. If your main pump runs often in heavy rain, choose a backup with higher GPH.

The battery

Most systems use a deep-cycle marine battery, often a group 27 or 31. A bigger battery runs longer. AGM batteries need less maintenance than flooded ones. Check what your pump’s maker recommends.

Alarms

An alarm tells you the backup is running, which means your main pump has a problem. Phone alerts are worth having if you travel.

Test it

A backup pump is only useful if it works. Here’s how to test a sump pump.

Common questions

How long does a battery backup sump pump run? It depends on the battery and how often the pump cycles. A fully charged deep-cycle battery can last from several hours of constant pumping to a day or more of occasional cycling.

Can I use a generator instead? Yes, but someone has to be home to start it. A battery backup works automatically. See the best generators for home backup power.

How often should I replace the backup battery? Many makers suggest every 3 to 5 years, sooner if it fails a test.