What Size Battery Bank is Required to Power a Refrigerator?

Jun 08, 2025

Wondering how big a battery bank you need to keep your camping refrigerators running without turning into a warm cupboard? Short answer: around 100Ah to 200Ah of lithium for a day’s use. But there’s more—start-up surges, battery types, and sneaky inefficiencies. Let’s plug into the details.

Calculating the Right Size Battery Bank for Your Refrigerator

Step 1: Understand Your Refrigerator's Energy Appetite

Finding Key Specs: Running Watts vs. Starting (Surge) Watts

Understanding how much power your fridge needs is the first step in sizing your battery bank correctly.

Most fridges draw more power at start-up than during regular operation. This initial demand, known as surge power, can be 2–3 times the running wattage.

For example, a fridge that runs at 400W might spike to 800–1200W when starting. You’ll need to account for this when choosing both your battery and inverter.

Dometic fridge with one door open, showing shelves filled with fruit, beverages, and fresh produce, on a white background.

The Importance of Duty Cycle: How Often Your Fridge Actually Runs

Fridges don’t run continuously—they switch on and off depending on internal temperature and external conditions.

This on/off cycle is known as the duty cycle. In most cases, fridges run for about 30–50% of the time throughout the day.

This can significantly reduce overall power consumption compared to running wattage alone.

Calculating Daily Energy Consumption (Watt-hours)

Start by checking the energy label or manual for your fridge’s daily usage, usually given in watt-hours (Wh).

As a rough guide, a standard fridge may use around 1,200Wh per day. This figure becomes the baseline for calculating your battery size.

AC vs. DC Fridges: Implications for Power Use & Inverters

Fridges designed for DC systems (common in off-grid setups and campervans) are generally more efficient.

That’s because they don’t require an inverter. Standard AC fridges do, and that conversion introduces losses—typically around 10–15%.

If you’re using an AC fridge, your battery bank needs to be larger to offset this loss.

Step 2: Key Factors That Determine Battery Bank Size

Desired Runtime: How Long Do You Need Power?

Think about how long you need your fridge to keep running without recharging. One day? A weekend?

Multiply your daily consumption by the number of days you want backup power. This gives you the total energy storage your battery bank needs to handle.

Battery Type Matters: Usable Capacity (Depth of Discharge - DoD) of Lead-Acid vs. Lithium (LiFePO4)

Different battery types have different usable capacities. This is known as Depth of Discharge (DoD).

Here’s a quick comparison:

Battery Type	Depth of Discharge	Efficiency	Lifespan (cycles)
Lead-Acid	50%	80–85%	300–500
Lithium-Ion	80–90%	95–98%	1,000–3,000

Lithium batteries are more expensive upfront but offer better performance and longer life.

Inverter Efficiency: Don't Forget This Loss for AC Fridges

Running an AC fridge off a DC battery requires an inverter. That conversion isn’t perfect.

Expect 10–15% energy loss during conversion. Factor this into your energy calculations, or you might end up underpowered.

Dometic fridge with both doors open, displaying empty interior shelves and compartments, on a white background.

Step 3: Putting It All Together – Sizing Your Battery Bank

Formula for Calculating Total Watt-hours (Wh) Needed

Use this basic formula:

Total Wh/day = Fridge Daily Consumption ÷ System Efficiency

For example, if your fridge uses 1,200Wh per day and your system efficiency is 85%, the actual demand is:

1,200 ÷ 0.85 = ~1,412Wh/day

Converting Watt-hours (Wh) to Amp-hours (Ah) Based on Battery Voltage

To convert watt-hours to amp-hours (Ah), use the battery voltage:

Ah = Wh ÷ Voltage

In this case:
1,412Wh ÷ 12V = ~118Ah

That’s the usable capacity. If you're using lead-acid batteries, you’ll need to double that due to the 50% DoD limit.

Example Calculation: Sizing for a Common Refrigerator Scenario

Let’s say:

Your fridge uses 1,200Wh/day
You want 2 days of autonomy
You're using a 12V lithium battery (80% DoD)

Total Wh = 1,200 x 2 = 2,400Wh
Adjusted for DoD = 2,400 ÷ 0.8 = 3,000Wh
Converted to Ah = 3,000 ÷ 12V = 250Ah

So, you’d need a 250Ah lithium bank. For lead-acid, you’d need around 500Ah.

Beyond the Basics: Optimising Your Setup & Practical Considerations

Choosing Components Wisely and Maximising Efficiency

Selecting the Correct Inverter Size (Especially Surge Capacity)

Make sure your inverter can handle your fridge’s surge requirement.

If the surge exceeds the inverter's rating, your fridge may not start at all. Aim for 2–3 times the running watts as a safe surge capacity.

Thetford BL compressor fridge with both upper and lower doors open, fully stocked with drinks, fruit, and containers, on a white background.

Tips for Reducing Your Refrigerator's Power Draw

Choose an A+++ rated model if buying new.
Improve air circulation around the fridge.
Minimise how often you open the door.
Keep it well-stocked—thermal mass helps efficiency.
Defrost regularly to maintain peak performance.

Factoring in Charging Sources (Solar, Alternator, etc.) for Long-Term Use

Even a well-sized battery won’t last forever if you can’t recharge it.

Consider adding solar panels, an alternator charger, or shore power input. For example, a 200W solar panel can recover about 800–1,000Wh/day, which is enough to run a camping fridge in decent weather.

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