How Long Will 100ah Battery Run 100W Appliance? + Calculator

A 12v 100ah lead-acid battery with a 50% DoD limit will run an appliance that requires 100W for about 5.4 hours

Keep reading I’ll explain how you can calculate how long will your 100ah battery run on a 100-watt appliance

How long will 100ah battery last – calculator

Battery Capacity
Battery Volts
Select Battery Type
Load Connected with inverter?
Total Load (watts)

Note! use my solar panel size calculator to find out what size solar panel you need to recharge your battery in desired hours with solar panels.


  • Inverter Efficiency: 90%
  • Lead-acid battery: 50% depth of discharge limit
  • Lithium (LiFePO4): 100% depth of discharge limit

Battery Depth of discharge DoD: is the percentage of the battery that has been discharged relative to the total battery capacity. The recommended depth of discharge limit for lead-acid, AGM, and gel batteries is about 50%. Only lithium (LiFePO4) batteries can be fully discharged to 100%.

How To Use The Calculator

  • Enter the battery capacity in amp-hours (Ah): in this case, it’ll be 100
  • Enter the battery voltage: is this a 12, 24, or 48-volt battery?
  • Select the battery type:  Select “Lead-acid” if you’re using a flooded or sealed (AGM or gel) lead acid battery. Select “Lithium (LiFePO4)” if you use a lithium-iron-phosphate battery.
  • load Connected with inverter?: Are you using an inverter to run the load or is the load connected directly through the battery?
  • Enter total load in watts: Enter the total load in watts (e.g 100 for 100 watts of output load)

After entering the information, click “Calculate” button to find out how long the battery last running a load.


how long will a 100ah battery run an appliance that requires 100w

Video – Solar battery 101

Steps To Calculate 100ah Battery Runtime On 100-Watt Appliance

Follow these steps to calculate the 100ah battery life/runtime while running a 100w load.


1- Converter battery ah into watt-hours (Wh). to calculate the battery capacity in watt-hours use this formula

Battery capacity in watt-hours = Battery amp-hours (Ah) * Battery Volts 

let’s say you have a 12v 100ah battery

100ah battery in watts = 100 * 12 = 1200 watt-hours 

2- Multiply the battery watt-hours by the battery depth of discharge limit( Default battery depth of discharge limit, Lead-acid battery: 50% DoD limit; Lithium: 100% DoD limit ). Let’s say you have a lead-acid type battery

Battery capacity in wh after DoD limit = 1200 * 50% = 600wh

3- Multiply the battery capacity after the DoD limit with the inverter efficiency rate to calculate the AC watt-hours ( Most of the inverters are about 90% efficient)

Battery AC watts = 600 * 90% = 540 AC watt-hours 

4- Divide the battery AC watt-hours by the total load connected. Let’s say 100-watt appliance is connected to your 100ah battery

100ah battery runtime on 100w appliance = 540 / 100 = 5.4 hours

How Long Will A 100ah Battery Run An Appliance That Requires 100W

here’s a chart on how long will a 12v, 24, and 48v 100ah lead-acid or Lithium battery will last on 100-watt load.

Battery CapacityBattery Type100ah Battery Runtime on 100w
12v 100ah Lead-acid5.4 hours
24v 100ah Lead-acid11 hour
48v 100ah Lead-acid21 hours
12v 100ah Lithium (LiFePO4)11 hour
24v 100ah Lithium (LiFePO4)21 hours
48v 100ah Lithium (LiFePO4)43 hours


  • A 12v 100ah lithium battery will run an appliance that requires 100W for about 11 hours

3 Steps To Extend Your Battery Lifetime

Battery life cycle count:

  • The battery’s storage capacity will decrease with every cycle ( a cycle is when you charge and discharge the battery to its DoD limit ).
  • if you have used your battery for a few hundred cycles then the result will be different. (this factor isn’t included in my above-given methods)

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I'm an experienced Sales Consultant with a demonstrated history of working in the renewables and environment industry. Skilled in Photography, Customer Service, and Sales.

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