How Long Will a 12v Battery Last With 500w Inverter?

Need an easy solution? Use our battery runtime calculator (given below) to find out how long will a 12v battery last with a 500 watt inverter.

Also, I’ll discuss how to calculate the 12v battery runtime time with a 500w inverter, and the factors which will affect the battery backup time.

How Long Will a 12v Battery Last With 500w Inverter – 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 the requied solar panel size in order to recharge your battery in desired hours.

Calculator Assumptions:

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

Keep reading… Now let’s dive into the factors which will affect the 12v battery runtime on 500 watt inverter.

Introduction To Deep Cycle Batteries

Deep cycle batteries are designed in a way to supply a small amount of power for a long period of time.

12v batteries come in a different capacities from 5Ah to 200Ah. We measure battery capacity in amp-hours (Ah), but the AC appliances or inverters are measured in watts.

How many watts does a 12v battery have? So to make the calculations easy, first of all, let’s convert Ah to Wh.

Formula: Watts = battery Ah x Battery volts.

Let’s take a 100Ah battery as an example for this guide.

100 * 12 = 1200 Wh

A 12v 100Ah battery is equal to 1200Wh. Make the calculations according to your battery size.

Now let’s discuss battery type and how they’ll affect the lasting time.

Watch this video to understand the basics of deep-cycle batteries.

Battery Type & Backup time

The most common 3 types of 12v batteries are Lead-acid, AGM, and lithium-ion batteries.

Lead-acid and AGM batteries have a DOD (Depth of discharge) limit of 50%. Which means you can only discharge them half.

Discharging them below 50% will decrease the lifespan of your batteries.

On the other hand, lithium batteries are designed in a way so you can discharge them up to 100% but 80% is recommended. Discharging them 100% will not affect the battery life.

Difference between lead-acid, AGM, and lithium batteries

Battery TypeDOD limitLife cycle

You can draw 50Ah from a 100Ah lead-acid or AGM battery but from a lithium battery, you can draw 80Ah – 100Ah.

Video – How to increase the lifespan of your 12v battery

Inverter Efficiency (DC vs AC watts)

The inverter is a device that converts the DC (direct current) from batteries into AC. which most of our household appliances required.

During this conversion, there will be a power loss because inverters are not 100% efficient. Most of the common inverter efficiency is 85%. This means a 100W inverter will draw 115 DC watts from the battery in order to run a 100W AC load.

Now multiply 0.85 by the total watt capacity of your battery. For this example, we’ll carry on with a 100Ah lithium battery with 100% DOD.

1200*0.85 = 1020 Wh

You’ll receive 1020 total AC watts from a 12v 100ah lithium battery.

Calculation – 500W inverter & AC load

Most experts do not recommend running an inverter at 80% of its capacity.

You can run your inverter at its full capacity, but it can damage the inverter in the long term. Because your 500w inverter will be consuming 600 DC watts from the battery, which is beyond its full capacity.

So, now let’s multiply 0.8 by the inverter’s total capacity. In this case, 500*0.8 = 400W. This means it’s recommended that you should connect 400W of AC load with your 500W inverter.

“Calculate how long will a 12v battery last with a 500 watt inverter using this formula”

Formula: Battery AC watts/output AC load = Estimated Runtime.

1020 / 400 = 2.5 hours or 150 minutes 

Chart – How long will a 12v battery will last with an inverter

12v Battery size with 500W inverterEstimated Backup time AGM or lead-acid battery 50% DOD limitEstimated Backup time lithium-ion battery 100% DOD limit
50Ah0.6 hours1.2 hours
100Ah1.2 hours2.5 hours
120Ah1.5 hours3 hours
150Ah1.8 hours3.7 hours
200Ah3 hours6 hours
300Ah3.6 hours7.2 hours

Note: this calculation is based on using your 500w inverter at its 80% capacity means with 400w AC load and also after converting the DC watts into AC watts.

Related FAQ’s

How long will a 12V battery run LED lights?

12v 50Ah battery is equal to 600 DC Watts and per LED light consumes 20 DC watts. 600/20 = 30 hours.

a 12v 50ah battery will run LED Light for 30 hours with a lithium battery or 15 hours with a lead-acid or AGM battery.

How long will a 100Ah battery run an appliance that requires 600W?

12v 100Ah battery is equal to 1200 DC watts and 1020 AC watts (1200*0.85 inverter efficiency).

100Ah battery will last 1 hour and 42 minutes while running an appliance that requires 600W.

How long will a 100-watt bulb run on a 12V battery?

12v 100ah battery will run a 100W bulb which requires AC watts for 10 hours. But, it will fully discharge the battery so if you have a lithium battery you can run it for 10 hours or for 5 hours with a lead-acid, AGM, or Gel battery.

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Chris Tsitouris is a renewable energy professional with 10+ years of experience as Director of Engineering at Solar Spectrum, previously working as Project Manager at SunPower and Energy Analyst at the National Renewable Energy Laboratory. As a thought leader, Chris has authored numerous articles and research papers.

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