# How long will a 12V 100Ah battery run a fridge?

I tested a 12V 100Ah battery to see how long it would power my fridge, and it lasted about 7 hours. However, this result is specific to fridges of similar size or energy usage.

The runtime of a fridge on such a battery depends on two factors:

1. The electricity usage of the fridge: Measured in kWh (kilowatt-hours) or Wh (Watt-hours), the electricity usage of your fridge varies based on factors like size, energy efficiency, room temperature, set temperature, fridge fill level, and door openings.
2. The usable capacity of the battery: Aside from the Rated Capacity of your battery (e.g., 1200 Wh), the Usable Capacity of the battery will also depend on its type or chemistry. While Lithium batteries can be fully discharged, Lead-Acid batteries can only supply 50% of their rated capacity before needing a recharge.

For instance, on average, you could run a 12V car refrigerator for about 100 hours on a 12V 100Ah Lithium battery, which can supply up to 1200 Wh of energy on a single charge.

On the other hand, if you run the same 12V fridge on a 12V 100Ah Lead-Acid battery, which can only supply 600 Wh of energy, you would only get about 50 hours of runtime before having to disconnect the battery.

Naturally, a bigger refrigerator will consume more energy and will drain either of these types of batteries much quicker.

Aside from the test on my specific refrigerator, documented below, I also did some research and gathered additional data. So, to provide some initial estimates, I’ve compiled this information into the following table, which categorizes refrigerators by their storage capacity and estimates the runtime on a 12V 100Ah battery:

I calculated the figures provided in the table using the electrical specifications and EnergyGuide labels of about 40 refrigerators. But please note that these are still rough estimates.

Later in this article, I will explain a more accurate method to get an initial estimate of how long one of these 12V 100Ah batteries will run your fridge, and even determine how many of them you’ll need to run your refrigerator reliably.

But before we get into that, let me first show you how my test went.

## Test Video: A 12V 100Ah Lead Acid battery VS. my refrigerator

Here’s a video version of my test. Check it out!

## Testing how long will a 12V 100Ah battery run a fridge

I wanted to see how long my fridge could run on a battery, so I used a 12V 100Ah Lead-Acid battery for the experiment.

Given that refrigerators like this one operate on AC (Alternating Current) power, and batteries exclusively provide DC (Direct Current) power, I needed to conenct the fridge to the battery using a power inverter.

This particular inverter was a Pure Sine Wave inverter with a Continuous Wattage rating of 500 Watts:

Check out my article on determining what size inverter you need to run your fridge.

To provide more perspective, here are some details about my specific test:

• My refrigerator is mid-sized, approximately 7 Cu. ft. (200L or 210 QT) in capacity, similar to most RV refrigerators.
• The refrigerator was filled to about 80% of its capacity.
• I set the fridge to its maximum cooling setting for the duration of the test.
• Throughout the test, I only opened the refrigerator’s door about once every hour.
• The fridge operated at a room temperature ranging from 86°F to 90°F (30°C to 32°C) on the day of the test.

Now, the day before this test, I used an electricity monitoring device and tested the energy usage of the fridge to get an initial estimate of how long the battery would be able to run it.

Electricity Usage Monitors

It turns out that the fridge consumes around 2.4 kWh of energy per day, equivalent to approximately 100 Wh of energy per hour of runtime.

This makes the fridge relatively inefficient in terms of energy usage compared to refrigerators of similar size, which typically consume about 1 kWh per day, or around 40 Wh per hour, based on my research.

But to be fair, the refrigerator was operating at a high room temperature, which meant it had to work harder to maintain its internal temperature.

In any case, this measurement indicated that, in theory, my battery should be able to run the refrigerator for about 6 hours.

I’ll explain how I was able to get this initial estimate later in this article.

Before running the test and getting actual results, I also wanted to make sure that the battery was fully charged. Using my Unit-T Multimeter, I checked its Voltage, which read 13.02 Volts, indicating a 100% state of charge for these types of batteries.

Also, this is a 12V 100 Ah battery, which means it has an energy capacity rating of 1200 Wh (12V x 100Ah). But since it’s a Lead-Acid battery, I can only make use of 50% of that energy capacity (600 Wh) to avoid shortening the battery’s lifespan.

Related: How many watt hours in a 100Ah 12V battery?

To ensure I maintain above a 50% state of charge on the battery, I connected my electricity monitor to the inverter and then plugged the fridge into the monitor to keep an eye on its electricity usage.

Once everything was ready, I flipped the switch on the inverter to kick off the test. Within a few seconds, I could hear the fridge’s compressor kicking in, which meant it was running on the battery just fine. All I had to do now was wait.

After about 1 hour and 15 minutes, I went back to check how much electricity the fridge had used. As you can see in the image below, it had used up 0.105 kWh (105 Wh) of energy during that time

I returned later to check the energy usage again, and after 6 hours and 36 minutes, the fridge had consumed 0.555 kWh (555 Wh) of energy.

But it’s important to remember that the refrigerator was operating on the battery through an inverter, which, like any device performing electrical conversions (in this case, DC to AC), isn’t 100% efficient.

Based on the documentation of my inverter, it was approximately 90% efficient. This means that the refrigerator would only use 90% of the energy drawn from the battery.

So, despite the refrigerator consuming only 555 Wh of energy, the battery likely supplied more than 600 Wh. To ensure the battery doesn’t drop below 50%, I decided to switch off the inverter and conclude the test.

Here’s the voltage of the battery after the test:

Now, If I had used a lithium battery instead, I wouldn’t have needed to worry about its state of charge and could have kept the refrigerator running until the battery was fully discharged.

In theory, this would have allowed me to run the fridge for approximately 13 to 14 hours on a single charge using a 12V 100Ah lithium battery.

12V-100Ah Lithium Batteries

However, it’s important to note that various factors can influence how long one of these batteries will power your refrigerator, even if it’s the same size as mine.

For instance, factors such as not setting the temperature to the maximum, providing more clearance around the fridge, lower room temperatures, and having a more energy-efficient refrigerator could significantly extend its runtime.

In any case, you can still get a reasonable estimate of how long a battery will run your refrigerator with some simple math. Let me show you how.

## How long will a battery run your refrigerator?

As I mentioned earlier, how long your fridge runs on a battery depends on two things:

1. How much energy your fridge uses.
2. How much energy your battery can provide on a single charge, a.k.a its Usable Capacity.

With these two bits of info, you can figure out the runtime using this simple formula:

Runtime (hours) = Usable Battery Capacity (Watt-hours) ÷ Refrigerator’s Hourly Energy Consumption (Watt-hours/hour)

### The Usable Capacity of your battery:

A battery typically has two key ratings:

1. Its “Voltage” rating, measured in “Volts” or “V”.
2. Its “Charge Capacity” rating, measured in “Amp-hours” or “Ah”.

Combined, these ratings determine the amount of Electrical Energy the battery can store, known as its “Energy Capacity”, measured in “Watt-hours” or “Wh”.

Energy Capacity (Watt-hours) = Voltage (Volts) x Charge Capacity (Amp-hours)

For instance, in my test, the battery is rated at 12V and 100Ah, which equates to an energy capacity rating of 1200 Wh:

Energy Capacity (Watt-hours) = Voltage (Volts) x Charge Capacity (Amp-hours)

Energy Capacity (Watt-hours) = 12 Volts x 100 Amp-hours

Energy Capacity (Watt-hours) = 1200 Watt-hours

However, this is the rated capacity of the battery, and not all of it is necessarily usable.

Let me explain.

Typically, the deeper you repeatedly discharge a battery, the fewer charge/discharge cycles it will have left.

This is why battery makers specify a specific Depth Of Discharge (DOD) for their batteries. Respecting this recommended DOD ensures an optimal battery lifespan, but also dictates the usable capacity of the battery.

For instance, according to the documentation provided with my battery, the manufacturer estimates that my battery should last approximately 650 charge/discharge cycles if I limit my usage to 50% of its capacity:

12V-100Ah Lithium Batteries

This means that if I want my battery to last for 650 cycles, I’ll only have access to 600 Wh of energy anytime I use the battery:

Usable Capacity (Wh) = Rated Capacity (Wh) x DOD (%)

Usable Capacity (Wh) = 1200 Wh x 50%

Usable Capacity (Wh) = 1200 Wh x 0.5

Usable Capacity (Wh) = 600 Wh

On the other hand, Lithium batteries inherently have more charge/discharge cycles, typically a couple of thousand cycles at a DOD of 100%. So, for example, if you have a lithium battery rated at 12V 100Ah, you’ll have access to 1200 Wh of energy on a single charge.

Here’s a table showing the recommended Depth Of Discharge (DOD) and usable capacity for common battery types:

### The Energy Consumption of your fridge:

There are a few ways to determine the energy usage of your refrigerator, the most accurate of which is to measure it like I did, using an electricity monitoring device such as the Kill-A-Watt.

Here’s a quick video I made documenting this:

Since I had already measured my fridge’s energy usage and found it to be around 100 Wh per hour, estimating the runtime was straightforward. I simply divided the usable capacity of my battery by this measurement:

Runtime (hours) = Usable Battery Capacity (Watt-hours) ÷ Refrigerator’s Hourly Energy Consumption (Watt-hours/hour)

Runtime (hours) = 600 Wh ÷ 100 Wh/hour

Runtime (hours) = 6 hours

As seen before, this estimate is pretty close to the actual results of my test.

If you don’t have an electricity monitor, you can still estimate your fridge’s energy usage using its electrical ratings. You can do this with a simple rule of thumb:

Hourly Energy Consumption (Watt-hours) = Wattage Rating (Watts) x 0.5 hours

And if the wattage of your fridge isn’t provided, you can calculate it using the voltage (Volts) and current (Amps) ratings:

Wattage (Watts) = Voltage (Volts) x Amperage (Amps)

For example, as you can see in the image below, my refrigerator has a Rated Voltage of 240 Volts and a Rated Current of 1 Amp:

Using these ratings, I can calculate the Wattage of my fridge as follows:

Wattage (Watts) = Voltage (Volts) x Amperage (Amps)

Wattage (Watts) = 240 Volts x 1 Amp

Wattage (Watts) = 240 Watts

And, using the Wattage of the fridge, I can estimate its hourly energy use:

Hourly Energy Consumption (Watt-hours) = Wattage Rating (Watts) x 0.5 hours

Hourly Energy Consumption (Watt-hours) = 240 Watts x 0.5 hours

Hourly Energy Consumption (Watt-hours) = 120 Watt-hours

Although this estimate is around 20% higher than my fridge’s actual energy consumption (100 Wh), it still provides a fairly accurate idea of what to anticipate.

In any case, if you would like your refrigerator to run longer on the battery, you can always expand your battery bank to reach the desired runtime, and you can calculate what size battery to run the fridge using the following formula:

Battery Size (Watt-hours)Refrigerator’s Energy Usage for the Desired Runtime (Watt-hours) ÷ DOD of the Battery (%)

For example:

According to the manufacturer, this Dometic 12V fridge consumes 18 Wh/h (18 Watt-hours per hour) on average.

As an example, let’s say I’m going camping for 5 days (120 hours) and I’m going to use Lithium batteries to power this fridge during my trip. This is the amount of energy that the 12V cooler will consume during this period:

5 days’ energy consumption (Watt-hours) = 18 Wh/hour x 120 hours

5 days’ energy consumption (Watt-hours) = 2160 Wh

Since I’m going to use a Lithium battery bank, I will have access to 100% of the battery’s capacity:

Battery Size (Watt-hours)Refrigerator’s Energy Usage for the Desired Runtime (Watt-hours) ÷ DOD of the Battery (%)

Battery Size (Watt-hours)2160 Wh ÷ 100%

Battery Size (Watt-hours)2160 Wh ÷ 1

Battery Size (Watt-hours)2160  Watt-hours

For this scenario, a suitable option would be the 12V 200Ah Li Time battery, which can supply up to 2400 Wh (12V x 200Ah) of energy on a single charge.

Another option would be to use 2 of these 12V 100Ah Li-Time batteries and wire them in parallel to make up a 12V 200Ah battery bank.

However, an even more practical and much cheaper option to get longer runtimes would be to run the refrigerator on solar power.

Since solar panels are cheaper than batteries, it would make more sense to use a combination of solar and batteries rather than just batteries, especially if you’re planning long camping trips or need energy backup for a larger refrigerator that consumes a lot of energy.

If the solar system is properly sized, all you’d need is enough battery backup for one day’s worth of your refrigerator’s energy usage, and the solar panels would produce enough energy every day to keep the battery bank charged.

You can check out my article on how many solar panels you need to run a refrigerator for a step-by-step guide on this.

##### Younes Anas EL IDRISSI

Younes Anas EL IDRISSI is the founder of RenewableWise.com and the driving force behind it. As a former Electrical Engineer and an energy self-sufficiency enthusiast, Younes' mission is to leverage his expertise and experience to simplify the complexities of solar energy and make it easily understandable for anyone looking into DIY energy solutions. Learn more about Younes and the story of RenewableWise here.

1. #### Yiola

Thank you for your www. I think it’s achieving your aim. Info here is digestible.

2. #### Peter Wright

Thank you for a very well explained article on the use of refrigerators for away from home trips. You seem to suggest (and are almost certainly correct), that all refrigerators are much of a muchness. I guess however that there must be a number that, due to insulation, internal volume, quality of manufacture, method of opening (top or side), etc., consume marginally less electricity than others. If there was one that you consider to be the best in this respect, which one would it be.
Regard
Peter Wright

3. #### Jeff Fallon

Thanks for the info. I am sizing components for my auxiliary battery system in my truck.
Regarding the Dometic Cooler, looks like it consumes 1.02A at 120v AC and 10.4 A at 12v DC.