How long will a 12 volt battery run a refrigerator?

So, you have a 12 Volt battery and a refrigerator, and you’re wondering “how long will the battery run the refrigerator?“.

Now, due to the many factors involved (ambient temperature, usage, age, type, and size of the refrigerator, etc..), there are no general or 100% accurate answers to this question. However, to get some pretty accurate estimates, all you need are the following pieces of information:

• The energy consumption of the refrigerator.
• The usable capacity of the battery.

After reading this article, you’ll understand how these pieces of information are relevant, how to determine them, and how to use them to estimate the amount of time you’d be able to run your refrigerator on your 12V battery.

Let’s dive in.

How long will a 12 Volt battery run a refrigerator?

In general, a 12V-50Ah battery can run a 2 cubic feet 12V fridge for 35 to 50 hours before it’s completely depleted. A 10 cubic feet RV refrigerator can run on the same battery for only 10 to 15 hours.

If the 12V battery is rated at 100Ah (Amp-hours), it should be able to run a 2 Cu. Ft. 12V fridge for 70 to 100 hours before it’s completely depleted, or a 10 Cu. Ft. RV refrigerator for about a day.

Before I provide a simple formula that you can use to get some estimates, it is important to note that:

• Batteries should not be completely depleted.
• And, different battery chemistries have different acceptable Depths of Discharge (DoD).

For example, if the 12V battery is a Lead-Acid battery, its recommended Depth of Discharge (or DOD for short) is only 50%, meaning that it is generally recommended to only discharge the battery to about 50% of its capacity. Discharging this type of battery below 50% will significantly reduce its life span.

On the other hand, if the 12V battery is a Lithium battery, it will inherently have more charge/discharge cycles than its Lead-Acid counterpart, and you’ll be able to use 80 to 100% of the battery’s rated capacity (80 to 100% DOD).

To illustrate this, the following table gives you an idea of how long you can run different types and sizes of refrigerators on a 12V battery without damaging it:

Fridge type	Fridge Size	12V Lithium Battery		12V Lead-Acid Battery
		50Ah	100Ah	50Ah	100Ah
12V Fridge	2 Cu. ft.	28 to 40 hours	55 to 80 hours	18 to 24 hours	36 to 50 hours
Mini-fridge	4 Cu. ft.	16 to 20 hours	32 to 40 hours	10 to 14 hours	20 to 28 hours
RV fridge	10 Cu. ft	10 to 12 hours	20 to 24 hours	6 to 8 hours	12 to 16 hours
Full-size fridge	18 Cu. ft.	6 to 8 hours	12 to 16 hours	4 to 5 hours	8 to 10 hours

To estimate how long a refrigerator would be able to run on a 12v battery, divide the battery’s usable capacity (Watt-hours) by the refrigerator’s estimated hourly energy consumption (Watt-hours):

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

The 2 variables in our formula are:

• Usable Battery Capacity (in Watt-hours or “Wh” for short)
• Hourly Energy Consumption of the refrigerator (in Watt-hours per hour or “Wh/hour” for short)

Let’s see what these variables represent and how to determine them.

Usable Battery Capacity:

A battery has 2 main ratings:

• The “Voltage” rating of the battery, which is measured in “Volts” or “V” for short.
• The “Charge Capacity” rating of the battery, which is measured in “Amp-hours” or “Ah” for short.

Together, these 2 ratings determine the actual amount of Electrical Energy that the battery can store, or its “Energy Capacity”, measured in “Watt-hours” or “Wh” for short.

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

In this article, we’re discussing 12V (Volts) batteries, but this rating only constitutes half of the equation. The actual capacity of the battery will also depend on its Amp-hours (Ah) rating.

For example, if our 12V battery is rated at 50 Ah, its Energy Capacity in Watt-hours is:

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

Energy Capacity (Watt-hours) = 12 Volts x 50 Amp-hours

Energy Capacity (Watt-hours) = 600 Watt-hours

If it’s a 12V-100Ah battery, its Energy Capacity is:

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.

As mentioned above, when a battery is repeatedly discharged to 0%, its lifespan is significantly reduced. So, if the longevity of your battery matters to you, you’ll probably not be able to use 100% of its rated capacity.

The following table provides some of the most common battery chemistries, their recommended Depth of Discharge (DoD), and their usable capacity (in Watt-hours):

Battery Chemistry	Recommended Depth of Discharge (DoD)	Usable Battery Capacity (Wh)
		12V-50Ah	12V-100Ah
FLA (Flood Lead-Acid)	50%	300 Wh	600 Wh
SLA (Sealed Lead-Acid)	50%	300 Wh	600 Wh
AGM (Absorbed Glass Matt)	50%	300 Wh	600 Wh
Li-Ion (Lithium Ion)	80%	480 Wh	960 Wh
LiFePO4 (Lithium Iron Phosphate)	80%	480 Wh	960 Wh

For example, if you have a 12V-50Ah lead-acid battery, the usable capacity of the battery is only 300 Watt-hours. If it’s a 12V-100Ah Lithium battery, on a recommended DOD of 80%, you’ll have access to 960 Watt-hours of energy if the battery is fully charged.

Now that we’ve quantified the amount of energy (in Watt-hours) that you might have access to, all we need is the amount of energy that your refrigerator consumes.

Refrigerator’s hourly energy consumption:

Appliances come with a couple of electrical ratings that indicate the rate at which they consume electricity:

• Voltage, which is measured in “Volts” or “V” for short (e.g., 12V, 120V)
• Current, which is measured in “Amps” or “A” for short
• Power, which is measured in “Watts” or “W” for short

The most important of which is the Power rating (or Wattage) of the appliance, which represents the rate at which the appliance consumes Electrical Energy (in Watt-hours).

For example, if a light bulb is rated at 50 Watts of power, and is left ON for 1 hour, the amount of energy (in Watt-hours) that it would have consumed by the end of that hour can be estimated as such:

Energy Consumption in 1 hour (Watt-hours) = Power Rating (Watts) x Usage Duration (hours)

Energy Consumption in 1 hour (Watt-hours) = 50 Watts x 1 hour

Energy Consumption in 1 hour (Watt-hours) = 50 Watt-hours

So, it could be said that the hourly energy consumption of our 50W light bulb is 50 Watt-hours per hour (50 Wh/hour).

Related: Appliance Energy Consumption Calculator

The problem with this is that a refrigerator’s energy consumption can’t be calculated as precisely as that of a light bulb or many other electrical appliances. This is because the compressor – which is the main electrical component of a fridge – has running cycles, i.e., duty cycles.

This means that although a fridge is plugged in all the time, it turns on and off in a more or less random way throughout the day, depending on things like:

• The ambient temperature
• The set temperature
• How full the fridge is
• Frequency of door openings, etc…

However, as a general rule of thumb, the average refrigerator only runs for about 20 mins every hour.

Therefore, if you know the Power rating of your refrigerator, you can simply divide it by 3 and you get the average hourly energy consumption in Wh/hour (Watt-hours/hour).

Consider the following example.

How fast will a 12 Volt cooler discharge your battery?

The average 12V fridge (1.6 to 2.5 Cubic feet) uses about 15 to 20 Wh of energy per hour. At this rate of energy usage, a 12V-100Ah battery can power a 12V fridge for about 3 days before the battery is completely discharged.

Here’s an example:

The manufacturer of this 1.6 cubic feet Euhomy 12V Refrigerator specifies 45 Watts as the Power usage.

As a general rule of thumb, this 12V fridge should be expected to consume about 15Wh of energy per hour.

Now, let’s say I want to run this fridge on this 12V-100Ah LiFePO4 Ampere Time battery.

We know that the recommended Depth Of Discharge (DOD) for a Lithium Iron Phosphate battery is 80%, so the usable capacity of this battery is about 960 Wh.

Now let’s estimate how long this 12V fridge would be able to run on the battery without damaging it.

Refrigerator Run Time (hours) = Usable Battery Capacity (Wh) ÷ Refrigerator energy consumption per hour (Wh/hour)

Refrigerator Run Time (hours) = 960 Wh ÷ 15 Wh/hour

Refrigerator Run Time (hours) = 64 hours

Theoretically, our fridge would be able to run for 64 hours on this battery.

How many batteries to run a refrigerator?

A typical 12V-50Ah battery could run a portable 12V refrigerator (2 Cu. ft) for one day and still have about a third to half of its capacity. However, bigger refrigerators would require a much bigger battery bank.

For example, a standard residential RV fridge (10 Cu. ft.) would need around 1000Wh (Watt-hours) per day to run. Which is equivalent to about 90Ah at 12 volts.

As mentioned in the sections above, the battery bank should be sized to supply energy to the refrigerator without exceeding a certain depth of discharge (80% for lithium batteries and 50% for lead-acid batteries).

The table below shows different refrigerator sizes, their estimated daily energy consumption, and how much battery capacity it would take to run them for 1 and 2 days:

Fridge type	Fridge Size	Daily Energy Consumption	12V Lithium Battery		12V Lead-Acid Battery
			1 Day	2 Days	1 Day	2 Days
12V Fridge	2 Cu. ft.	350Wh	40Ah	80Ah	60Ah	120Ah
Mini-fridge	4 Cu. ft.	600Wh	60Ah	120Ah	100Ah	200Ah
RV fridge	10 Cu. ft	1000Wh	120Ah	230Ah	180Ah	360Ah
Full-size fridge	18 Cu. ft.	1500Wh	200Ah	400Ah	300Ah	600Ah

Note that the table uses 50% DoD (depth of discharge) for lead-acid batteries and 80% for lithium batteries.

How to size a battery bank for a refrigerator?

If you want to determine how big of a battery bank you need to run a refrigerator, you need 3 pieces of information:

• The refrigerator’s estimated daily energy consumption.
• The number of days you want to run the refrigerator.
• The chemistry of the battery you’re going to use.

For example:

According to the manufacturer, this Dometic 12V fridge consumes 1.5Ah/h (1.5 amp-hours per hour).

Let’s say I’m going camping for 3 days (72 hours) and I’m going to use lithium batteries to power it during my trip.

3 days energy consumption @ 12V (Ah) = 1.5 Ah/hour x 72 hours

3 days energy consumption @ 12V (Ah) = 108 Ah

During these 3 days, the refrigerator is expected to consume around 108Ah at 12 Volts.

Since I’m going to use a lithium battery bank, I only have access to 80% of the battery’s capacity. The total capacity of the battery bank can be calculated as such:

Battery Bank Capacity @ 12V (Ah) = Energy Consumption @ 12V (Ah) ÷ Recommended DOD (%)

Battery Bank Capacity @ 12V (Ah) = 108 Ah ÷ 80%

Battery Bank Capacity @ 12V (Ah) = 108 Ah ÷ 0.8

Battery Bank Capacity @ 12V (Ah) = 135 Ah

This means that the 12V lithium battery bank I need to run my refrigerator for 3 days would have to be rated at 135 Ah or higher.

If you have a bigger refrigerator, it would probably make more sense to use solar energy. For more information about that, click here or go to the section below.

How to make the battery last longer?

There are a few things that you can do to preserve energy and potentially extend the usage time of the refrigerator:

Shade and insulation:

Insulation materials are a simple and cheap way to increase battery longevity and protect your refrigerator.

When a refrigerator is placed under direct sunlight, not only will it consume way more energy, but it will also be at risk of failing due to the excessive workload.

If your refrigerator is going to be sunlit, make sure to use a reflective insulation shield.

Cool the fridge down before plugging it into the battery:

Refrigerators need a lot of energy to initially cool down. The battery would last longer if it’s only maintaining the low temperature inside the refrigerator rather than supplying the energy needed to create it.

Most 12V fridges have a 120/220 VAC plug, so if you’re planning on running one on batteries, consider plugging it into the wall and cooling it down at home.

How much clearance around the fridge?

Refrigerators cool down the air inside by performing a temperature exchange with the outside environment. For this to happen, a certain amount of airflow is required.

If the fridge is surrounded by stuff, the fridge will have to work harder to perform the required amount of heat exchange, and it will therefore use more energy.

So make sure to leave at least 2 inches of clearance on each side of the fridge, especially the part from which the heat dissipates into the air (generally located at the rear of the refrigerator).

Fill up your fridge

It might sound counter-intuitive, but empty fridges consume more energy than full ones. This is because it takes more energy to keep the air cold than it takes to keep the food cold. Especially if the fridge is frequently opened.

So, make sure to take advantage of the cubic footage of your refrigerator.

Consider using solar power:

Let’s say you’re going camping for a couple of days and have a battery that can run your fridge for 1 day only.

It’s much cheaper to buy a solar panel than to double the size of your battery. Plus, a solar panel/battery combo can potentially run your refrigerator forever.

This brings us to the next section.

How much solar power do I need to run a refrigerator?

To run a small 12V refrigerator (2 Cu. ft.) on solar power, you would need a 100W solar panel and a 12V-50Ah battery. For a bigger refrigerator such as an RV fridge (10Cu. ft.), you would need 200 to 300 watts of solar power and 120 to 180 Ah of battery capacity.

However, you also need a solar charge controller, and in case you have a refrigerator that only works on AC, you’ll also need an inverter.

For more information, please refer to this article: How many solar panels do you need to power a refrigerator?