Sump Pump Battery Backup

A sump pump plays a critical role in keeping certain homes dry, especially during heavy rains or rising groundwater levels. Installed in the lowest part of your basement or crawlspace, a sump pump collects water and directs it away from your home, preventing flooding and water damage. However, when storms hit, power outages often follow—leaving your sump pump unable to do its job.

Sump pump power backup is essential. In this article, we’ll explore typical electrical requirements, different solutions, and why a solar generator may a good fit.

Understanding the Electrical Requirements of Your Sump Pump

Choosing the right backup power solution starts with understanding how much power your sump pump requires to function.

• AC Power Most sump pumps require AC (alternating current) power to operate. Any battery will require a separate inverter device to convert from DC to AC electricity.
• Voltage: Standard sump pumps typically run on 120 volts in the U.S., which is compatible with most backup power systems.
• Running Power: Most residential sump pumps need 600–1,500 watts to operate, depending on their size and efficiency.

Surge Power: Another Requirement To Plan For

When a sump pump starts, it temporarily draws much more power than it uses during normal operation. This startup surge can be 2–3 times the pump’s running wattage.

For example: A pump with a running wattage of 800 watts may need 2,400 watts at startup. Your backup power source must be able to handle both the surge and running wattage to ensure uninterrupted operation.

Automatic Switching: UPS Functionality

A critical feature for any sump pump backup system is automatic switching, which ensures uninterrupted operation when the power goes out. Systems with Uninterrupted Power Supply functionality are designed to detect power outages instantly and switch to backup power without manual intervention. This seamless transition prevents delays that could leave your basement vulnerable to flooding.

How It Works

• During normal operation, the system draws power from the grid to run the sump pump.
• If the grid fails, the system automatically shifts to battery or generator power to keep the pump running.
• Once grid power is restored, the system reverts to using it and, recharges the backup battery.

How Long Can Your Sump Pump Run on Backup Power?

The runtime capability of your sump pump backup system is crucial. This determines how long your pump can keep working when the grid is down—a critical factor during prolonged storms or emergencies.

Why Runtime Matters

• Extended Outages: Severe weather or natural disasters can cause outages lasting hours or even days. A backup system with insufficient runtime may fail while water levels are still rising.
• High Demand During Storms: Heavy rainfall can cause your sump pump to cycle frequently, draining the backup power faster than usual.

What Affects Runtime?

Several key factors determine how long your backup system will last:

• Energy Capacity: The storage capacity of your backup is the main determinant of backup runtime. Some backup options also allow for indefinite runtime, by refilling fuel or solar charging.
• Pump Duty Cycle: Sump pumps usually run intermittently, not continuously. A pump operating 25% of the time will use less energy, extending the runtime compared to constant operation.

Backup Power Sources for Sump Pumps

Here are the most common ways to power your sump pump during an outage:

• Traditional Lead-Acid Batteries

  Available for decades, these include flooded lead-acid and sealed AGM (Absorbent Glass Mat) batteries. Flooded lead-acid batteries are cost-effective but require regular maintenance, such as topping off with distilled water. AGM batteries don't have the same maintainence requirements, are safer to handle, but are more sensitive to ambient heat and require smart charging systems that will avoid damage.

  • Running Power and Voltage: Lead-acid batteries store energy as DC (direct current) power. To run a sump pump, which requires AC (alternating current) power, the system uses an inverter to convert DC from the battery into AC. This ensures compatibility with the 120V standard used by most residential sump pumps.
  • Surge Power: Lead-acid batteries can handle startup surges, but their performance depends on the quality and capacity of the battery bank. Proper inverter sizing is also critical to support the surge demands of the pump.
  • Runtime: Typically offers 4–12 hours of runtime, depending on battery capacity and pump duty cycle. However, longer outages will require larger battery setups or additional solutions.
  • Automatic Switching: Many traditional battery systems include UPS functionality, ensuring seamless switching during outages.
  • Additional Considerations: Requires regular maintenance for flooded lead acid batteries, and replacement every 3–5 years. Charging times are 4-8 times longer than lithium batteries², which may limit their ability to recover during intermittent power outages.

• Fuel-Powered Generators

  Fuel-powered generators convert fuel like gasoline, propane, or diesel into electricity, with some models supporting multiple fuel types. Inverter generators, a subtype, offer improved efficiency and stable power for sensitive electronics.

  • Running Power and Voltage: Easily meets running and surge power requirements for any sump pump. Most models are compatible with 120V systems.
  • Surge Power: Handles significant startup surges without issue, making them highly reliable for large pumps.
  • Runtime: Provides indefinite runtime as long as you have a steady fuel supply, making it ideal for extended outages if replacement fuel is available.
  • Automatic Switching: Fuel generators can be setup with an Automatic Transfer Switch to turn on when the grid goes down. There is usually a delay of at least 10-30 seconds until backup power is available.
  • Additional Considerations: Requires regular maintenance, produces noise and emissions, and must be operated outdoors or in a ventilated enclosure.

• Solar Generators

  Solar generators combine renewable energy with backup power, storing electricity in high-capacity batteries that can be recharged by solar panels.

  • Running Power and Voltage: Can meet standard running and surge power requirements for sump pumps when properly sized.
  • Surge Power: Usually offers surge capacity of 2-3 times their continuous output capability, helping to handle pump startup.
  • Runtime: Battery capacity is available up to multipe days, and with solar panels can provide indefinite runtime with good sunlight.
  • Automatic Switching: Many solar generators include UPS functionality, allowing seamless transition to battery power during an outage while charging the battery when the grid is operational.
  • Additional Considerations: Higher upfront costs which can be defrayed with longer lifetimes and greated versatility. Reduced efficiency during cloudy weather or prolonged storms make solar generators less effective in areas with limited sunlight if solar recharging is desired.

Other steps to take

If your sump pump fails due to overwhelming water volume, mechanical issues, or other problems, a second sump pump can be a lifesaver.

• Redundancy: Acts as a backup if the primary pump fails or is overwhelmed.
• Increased Capacity: Helps manage heavy water flow during severe storms.
• Flexible Pairing: Combine with a separate power source for greater reliability.

To learn more about dual-pump systems, visit this backup sump pump guide by North Dakota State University.

Final Thoughts

A reliable sump pump backup system is crucial for protecting your home from flooding during power outages. Whether you choose a battery backup, solar generator, or fuel-powered generator, ensure your system meets the pump’s power and surge requirements.

For maximum protection, pair your backup power with a second sump pump to tackle overwhelming water flow or mechanical failures. With these measures in place, you’ll enjoy peace of mind knowing your basement is safe, even when the unexpected happens!