Well Pump Battery Backup: How to Choose the Right Battery System

When the power goes out, a home or property that relies on a well can lose access to running water. That can affect drinking water, showers, toilets, livestock watering, irrigation, and everyday household needs. A backup battery system can help keep water available, but the right setup depends heavily on the type of pump and how the water system is designed.

Not all well pumps use the same amount or type of power. A full-size household well pump may run on 120V or 240V AC and need a large surge of power to start. A solar well pump, transfer pump, or small DC water pump may have very different battery requirements. Some systems need enough backup power to pressurize a whole home, while others only need to move water into a storage tank or keep remote monitoring equipment online.

Because of those differences, choosing a well pump battery backup is not as simple as matching a battery to the word “pump.” You need to understand:

• the pump voltage
• running power
• startup demand
• runtime needs
• and charging source before selecting a battery system.

In this guide, we’ll walk through the main types of well and water pump backup systems, when a compact 12V battery may be enough, when a larger inverter-based battery bank is required, and how to choose the right Battle Born battery solution for your application.

TL;DR

• Well pump battery backup can keep water flowing during power outages or supply water at off-grid properties.
• Small DC pumps, well controls, and cistern transfer pumps may run from compact Battle Born Base Series batteries.
• Many residential well backups can use a bank of 100Ah 12V Battle Born Batteries, configured for 12V, 24V, or 48V operation.
• Larger pumps, longer outages, and whole-property systems may benefit from the greater capacity of 270Ah GameChanger batteries.
• Size the system for the pump’s running power, startup demand, daily energy use, and desired runtime—not voltage or well depth alone.

Table of Contents

• What Type of Well Pump Are You Backing Up?
• 120/240V Household Well Pump Backup Is a System, Not Just a Battery
• When a 12V, 24V, or 48V DC Well Pump Makes Sense
• Using a Cistern as a Water Battery
• How Much Runtime Do You Actually Need?
  • For an Existing Well
  • New Well Installation
• How to Size the Battery Bank
  • Inverter Loss Consideration
  • How Amp-Hours Relate to Kilowatt-Hours
• How to Recharge Well Pump Backup Batteries
  • Charging From Grid or Generator Power
  • Charging With Solar Power
• Choosing Battle Born Batteries for Well Pump Backup
  • Lithium vs. Lead-Acid for Well Pump Backup Power
  • Base Series Batteries for Small Pumps and Controls
  • 100Ah Batteries for Typical Well Backup Systems
  • 270Ah GameChanger Batteries for Larger and Longer-Lasting Systems
  • Built for Reliable Deep-Cycle Power

What Type of Well Pump Are You Backing Up?

Before choosing a battery, identify the type of pump you need to power. Well pump battery backup can mean anything from a full-size household well pump to a small 12V DC pump moving water into a storage tank.

This distinction matters because a small 12V battery may work well for a small DC water pump, but it will not directly power a 120V or 240V household well pump. Larger AC well pumps need a complete backup power system, not just a battery connected to the pump.

^This is the top of a submerged 240v well pump; pumps like this require a lot of power to run and a full power system of batteries and inverters to operate as battery backup.

120/240V Household Well Pump Backup Is a System, Not Just a Battery

A battery stores energy, but it does not automatically make that energy usable for every load.

If you have a 240V AC well pump, a 12V battery cannot power it directly. You need an inverter that converts DC battery power into AC power. If the pump requires 240V, the inverter system must be able to provide the correct voltage. It also needs enough surge capacity to start the pump.

⚡️Learn more about when a split-phase inverter is required for 120/240V equipment.

Then the battery bank must be large enough to support that inverter load. A large AC motor can pull high current from a low-voltage battery bank. At 12V, large loads require very high DC current. That can mean larger cables, more voltage drop concerns, and more stress on the system. For bigger loads, 24V or 48V battery systems may be more practical than 12V systems.

You also need to think about how the system connects to the pump circuit. Backup power for a hardwired well pump should be installed safely and in compliance with electrical codes. In many cases, this may require a transfer switch, critical-load panel, licensed electrician, or professional installer.

Our customers build reliable backup and off-grid systems with our batteries every day, and many run well pumps successfully. However, this type of system needs to be properly designed and installed for reliable operation. 

When a 12V, 24V, or 48V DC Well Pump Makes Sense

If you are designing a new off-grid property or dedicated backup water system, a DC well pump may be a simpler alternative to powering a conventional AC pump.

Submersible well pumps are now available for 12V, 24V, and 48V battery systems, including models designed for direct use with batteries, solar power, or both.

These pumps still require a compatible pump controller, but they do not require an inverter to convert battery power from DC to AC. Eliminating that conversion can reduce energy losses, system complexity, standby consumption, and the number of components that could fail. Some DC pump controllers also provide dry-run protection, low-voltage protection, and connections for tank-level or pressure controls.

A 12V pump may be appropriate for a small transfer pump, shallow well, or low-flow agricultural system. Larger or more distant installations often benefit from 24V or 48V operation because the higher voltage reduces current and voltage drop. This allows the system to deliver the same power with more manageable conductor sizes.

Surface-mounted DC pumps can also draw from cisterns, tanks, ponds, spring boxes, and shallow wells. However, a surface pump can typically lift water only about 20–25 feet under favorable conditions. This limit is imposed by atmospheric pressure, and elevation, pipe friction, air leaks, and other real-world conditions can reduce it further. If the water level is deeper, a submersible pump must be placed in the well to push the water to the surface.

DC pumps are not necessarily the best choice for replacing an existing household well pump. However, when off-grid operation is a priority and the water system is still being designed, pairing a DC submersible pump with batteries and solar can create an efficient, reliable system without the added complexity of an inverter. 

^DC water pumps are common and work well and efficiently; however, they are generally not capable of drawing from deep wells. Operating from a cistern or backup tank, they work great. 

Using a Cistern as a Water Battery

Another way to keep water available during a power outage is to store it while power is available. This is common in dry regions where the well may run dry, or where water is pumped by solar only during the day. The primary well pump keeps a cistern or large storage tank full during normal operation. If the power fails, a separate DC transfer or booster pump draws from the stored supply and pressurizes the water system.

Because the backup pump does not have to lift water from deep in the well, it typically requires far less power than the primary pump. A properly sized 12V, 24V, or 48V pump may be able to operate directly from batteries without an inverter. This can reduce startup surge, battery capacity, and system cost compared with powering an existing 120V or 240V well pump. The backup pump still needs to provide the required flow and pressure, and the system may need a pressure tank, pump controller, dry-run protection, and a safe way to switch between water sources.

The main limitation is that the available water is restricted to the usable capacity of the tank. Backup duration should therefore be based on the cistern's usable volume and the property's essential daily water use. The tank also needs appropriate protection from freezing and contamination. For properties where a full-size well pump is difficult to back up, however, a cistern can turn a demanding electrical load into a much smaller and more manageable battery-backed pumping system.

Tanked water is basically a "water battery" and is a common way to back up a water supply. 

How Much Runtime Do You Actually Need?

The most accurate way to estimate runtime depends on whether the well system already exists or is still being designed.

For an Existing Well

Measure how much electricity the pump consumes during normal use. A power meter or energy monitor can record the pump’s actual running wattage, cycle duration, and total kilowatt-hours used over several representative days. Because many well pumps are hardwired, often at 240V, this measurement may require an electrician or a properly installed circuit-level energy monitor.

Measure long enough to capture normal variations, including showers, laundry, irrigation, livestock watering, and other major water uses. Actual energy consumption is more useful than assuming the pump runs for a certain number of hours each day.

Once you know its daily consumption, you can choose between two backup strategies:

• Maintain normal water use: Size the battery bank to replace the well’s typical daily energy consumption for each day of expected outage.

• Provide essential water only: Plan to limit showers, laundry, irrigation, and other high-volume uses. This can substantially reduce the required battery capacity.

For example, if monitoring shows that a pump uses 2kWh per day during normal operation, three days of full-use backup would require at least 6kWh of usable energy, plus capacity for inverter and system losses. If emergency conservation cuts pump use in half, the same battery capacity could last considerably longer.

If the Well Has Not Been Installed Yet

If the well has not been installed yet, estimate runtime from expected water demand and pump performance. 

Start with the number of gallons the property will use each day, then divide that amount by the pump’s expected flow rate:

Estimated pump runtime = Daily water demand ÷ Pump flow rate

A property using 300 gallons per day with a pump delivering 10 gallons per minute would require roughly 30 minutes of pumping per day. If the selected pump draws 2,000W while running, that equals approximately 1kWh of daily pump energy before accounting for inverter and wiring losses.

However, flow rate alone does not determine pump power. The estimate should also account for:

• Well depth and pumping water level

• Vertical lift from the water level to the pressure tank or storage tank

• Required household water pressure

• Pipe length, diameter, and friction loss

• Desired flow rate

• Pump and motor efficiency

• Pump voltage and horsepower

• Pressure tank settings and pump cycling

Together, elevation, water level, pressure, and pipe resistance determine the system’s total dynamic head. A well contractor can use that figure with the manufacturer’s pump curve to select a pump and estimate its input power at the expected operating point.

☝️Remember that battery runtime and inverter capacity answer two different questions. Daily energy use determines how long the backup can operate, while running wattage and motor startup surge determine whether the system can start and run the pump at all.

How to Size the Battery Bank

Once you know the well system’s daily energy use, multiply it by the number of days you want the backup to last:

Usable battery capacity needed (kWh) = Daily energy use (kWh) × Days of backup

For example, suppose a small 12V well pump and its controls use approximately 0.5kWh per day. Providing three days of backup would require:

0.5kWh × 3 days = 1.5kWh of usable energy

The battery bank must be somewhat larger than this to account for conversion losses and the amount of battery capacity you plan to use.

Inverter Loss Consideration

If the pump operates directly from 12V DC, inverter losses may not apply. If it operates through an inverter, use:

Nominal battery capacity (kWh) = Daily energy use × Backup days ÷ Inverter efficiency ÷ Usable battery percentage

With a 90%-efficient inverter and 10% of the battery capacity retained as an operating reserve:

0.5kWh × 3 ÷ 0.90 ÷ 0.90 = 1.85kWh

This example would require at least 1.85kWh of nominal battery storage, plus any desired reserve.

How Amp-Hours Relate to Kilowatt-Hours

Battery capacity is often listed in amp-hours, but amp-hours only describe electrical charge. You also need the battery voltage to determine how much energy it stores. Our guide to converting watt-hours and amp-hours explains the relationship in more detail.

Battery energy (kWh) = Battery voltage × Amp-hours ÷ 1,000

A 12.8V, 100Ah lithium battery stores approximately:

12.8V × 100Ah ÷ 1,000 = 1.28kWh

Two 12.8V, 100Ah batteries would provide approximately:

12.8V × 200Ah ÷ 1,000 = 2.56kWh

That would cover the calculated 1.85kWh requirement in this simplified example while leaving some additional capacity. Always round up to a complete, manufacturer-approved battery-bank configuration.

This example assumes the battery bank and connected equipment can also supply the pump’s operating current. A system can have enough stored energy for several days but still be unable to operate a pump if the batteries, wiring, controls, or inverter cannot deliver the required power.

How to Recharge Well Pump Backup Batteries

A well pump battery backup also needs a reliable way to recharge after use. The appropriate charging source depends on whether the batteries serve primarily as emergency backup or supply the well every day.

Charging From Grid or Generator Power

When grid power is available, an AC battery charger can keep the battery bank charged and ready for an outage. Systems that already use an inverter may use an inverter-charger instead. This combines the inverter and battery charger into one unit and may automatically switch the well system to battery power when grid power fails.

A generator can supply the same charger or inverter-charger during an extended outage. The charger should be compatible with the battery chemistry, bank voltage, and recommended charging current. It should also be appropriately sized for the generator so the generator is not overloaded.

⚡️ Learn more about how to charge lithium batteries properly.

A larger charger restores the battery bank more quickly, while a smaller one may take longer but place less demand on the grid connection or generator.

Charging With Solar Power

Solar panels can recharge the battery bank through a compatible solar charge controller. The controller regulates the panels’ output and applies the correct charging profile to the batteries.

For a backup system that is rarely used, the solar array may not need to replace an entire day’s water-pumping demand in a single day. A relatively small array can maintain the batteries and gradually recharge them between outages. The appropriate size depends on how quickly the system needs to recover and how much sunlight is available at the site.

For an off-grid well, solar has a different job. The array must typically generate enough energy to replace the well system’s expected daily consumption, while also accounting for:

• Available peak sun hours

• Seasonal changes in sunlight

• Panel orientation and shading

• Charge-controller and battery losses

• Cloudy-weather reserve

• Any other loads using the same battery bank

For an off-grid well, the solar array should produce enough energy to replace the well system’s expected daily consumption, with additional capacity for charging losses, seasonal changes, cloudy weather, and unusually heavy water use.

⚡️ Learn more about how to size a solar power system based on daily energy use.

Whether the system charges from the grid, a generator, solar, or a combination of sources, the charger and charge controller must match the battery bank’s voltage and approved charging specifications.

Choosing Battle Born Batteries for Well Pump Backup

Once you know the well system’s operating power and required battery capacity, you can choose a battery based on the size and design of the system. A small DC transfer pump may need only a compact battery, while a deep-well pump operating through a 240V inverter may require a much larger bank.

Lithium Vs. Lead-Acid for Well Pump Backup Power

Lithium batteries provide more usable capacity, faster charging, longer cycle life, and less maintenance than lead-acid batteries. They also maintain steadier voltage under heavy loads, helping support well pump startup and inverter operation without requiring an oversized battery bank.

Lead-acid may cost less upfront, but its heavier weight, limited usable capacity, and shorter lifespan often cost you more time and money in the long run. 

⚡️ Learn more in our comparison of lead-acid vs. lithium-ion batteries

Base Series Batteries for Small Pumps and Controls

Battle Born Base Series batteries are available in 10Ah, 20Ah, and 30Ah capacities. At 12.8V nominal, they provide approximately:

• 10Ah: 128Wh

• 20Ah: 256Wh

• 30Ah: 384Wh

These compact batteries are best suited to smaller, lower-current parts of a water system rather than conventional deep-well pumps. Potential applications include:

• Well controls, monitoring equipment, and communication systems

• Valves, alarms, and other supporting equipment

• Small 12V transfer or booster pumps

• Shallow-well systems with modest power requirements

• Livestock watering and light agricultural pumping

• Solar-powered remote watering or monitoring installations

• Moving water from a storage tank or cistern

For example, a low-power 12V transfer pump could operate directly from a Base Series battery without an inverter, provided its running current and startup demand remain within the battery’s output limits. A solar charge controller could then recharge the battery from a small panel, creating a compact off-grid water system.

The battery still needs to be matched to the pump or control system. Confirm its voltage, running current, startup current, expected runtime, and charging requirements before selecting a Base Series battery.

^Many modern water systems have electronics that need to remain powered even during outages; small 12V batteries are usually the choice for these applications. 

100Ah Batteries for Typical Well Backup Systems

For most residential well pump backup systems, Battle Born’s 100Ah batteries provide a more practical starting point. Each 12.8V, 100Ah battery stores approximately 1.28kWh of nominal energy.

A dedicated well backup might use two to six 100Ah batteries, depending on pump power and desired runtime.

The batteries can be configured around the needs of the pump and inverter. A 12V bank may work well for a smaller system, while 24V or 48V configurations reduce DC current and are often more practical for larger inverters. A 24V bank requires batteries in matched series pairs, so it would commonly use two, four, or six 12V batteries. Learn more about wiring batteries in series or parallel to change bank voltage or capacity.

These systems can support:

• 12V DC well and transfer pumps

• Conventional 120V pumps through an inverter

• 240V well pumps through a compatible split-phase inverter system

• Pressure controls and related water-system equipment

• Dedicated well backup or a larger essential-load system

A 100Ah battery bank can remain charged from the grid using a compatible charger or inverter-charger. It can also recharge from solar through a solar charge controller. For an off-grid property, the solar array should be sized to replace the well’s expected daily energy use. For standby backup, a smaller array may be sufficient if it has time to maintain and gradually recharge the batteries between outages.

Battery capacity is only part of the design. The complete bank must also deliver enough current to operate the inverter and start the pump motor. The inverter must produce the correct voltage, supply the pump’s running power, and handle its startup surge.

270Ah GameChanger Batteries for Larger and Longer-Lasting Systems

For high-demand wells, longer outages, or systems that also power other essential property loads, the Battle Born 270Ah GameChanger battery provides considerably more capacity in each battery. One 12.8V, 270Ah battery stores approximately 3.46kWh of nominal energy.

GameChanger batteries are well suited to systems that:

• Operate larger 120V or 240V well pumps through an inverter

• Need several days of water availability

• Support a home, ranch, farm, or remote property

• Combine well backup with refrigeration, lighting, communications, or other essential loads

• Recharge from a substantial off-grid solar array

• Require high power output as well as longer runtime

The larger capacity can reduce the number of individual batteries and connections needed to build a high-capacity bank. Multiple GameChanger batteries can also be incorporated into larger system designs when additional storage or higher system voltage is required.

Built for Reliable Deep-Cycle Power

Across the product line, Battle Born batteries use lithium iron phosphate chemistry, premium cylindrical cells, and an integrated battery management system. Cylindrical cells dissipate heat effectively, tolerate vibration, and divide the battery’s energy among many smaller cells. LiFePO₄ chemistry also provides the thermal stability and long cycle life that matter in backup and off-grid power systems.

⚡️ Learn more about what is inside a Battle Born battery.

The right choice ultimately depends on both energy and power.

• Base Series batteries can support compact controls and light-duty pumping.
• Banks of 100Ah batteries fit many residential well backups
• GameChanger batteries provide the capacity and output needed for larger pumps, longer outages, and whole-property systems.

Before purchasing, confirm the proposed battery, charger, inverter, and pump configuration with the equipment manufacturers or a qualified system designer.

Build a Reliable Well Pump Power System

Battery backup for a well pump starts with the load, not the battery. Confirm the pump’s voltage, running power, startup requirement, and expected daily energy use.

From there, you can determine whether the application needs a compact Base Series battery, a bank of 100Ah batteries, or a larger GameChanger system—and whether it should recharge from the grid, a generator, solar, or a combination of sources.

Ready to build a reliable well pump backup or off-grid water system? Explore Battle Born LiFePO4 batteries, or contact our Technical Specialists for help matching the battery bank, charging source, and inverter to your application.