10 Ways to Power Your 12V Fridge for Longer

Sometimes, cooling down can require cranking the heat – and when it comes to staying fresh alfresco, the 12V fridge is as power-hungry as it is popular! They’re the ultimate comfort in camping. Menus can expand to include pretty much anything you can cook at home, as long as you can fit it in the fridge! These days, portable fridges are extremely popular additions to any camping and 4WD arrangement – and if you head out regularly, they become well and truly worth the expense.

However, a fridge requires a fair bit of energy to run – it’s almost always the highest consumer, and you need to get that power from somewhere. There is a lot of focus on solar panels and batteries, but there are a number of ways you can reduce the energy consumption from your 12V fridge.

In this blog, we defrost our top 10 tips for how to reduce the energy consumption of your 12V fridge off the grid – so you can keep the cans cold and perishables fresh for longer. From kicking back on the boat to basking in the balmy bliss of the campsite, read on for a refresher on fridge maintenance facts and energy-saving hacks to keep the tucker in date.

A man fetching drinks and iceblocks from an icebox for three children.These days, portable fridges are extremely popular additions to any camping and 4WD arrangement. Image: Dometic

How Much Power Does a Fridge Need?

There are many different factors that affect the energy consumption of a 12V fridge: size, compressor style, ambient temperature, insulation thickness, the temperature they are set to cool to, what you are using it for – the list goes on. However, most will consume in between 1 amp and 6 amps (with 2.5 amps being fairly average) per hour when running. That said, a fridge won’t usually run 100% of the time, so it only pulls that current when the compressor is on.

Most fridges are loud enough to hear within a few metres. Again, the cycle time varies considerably, but on average they run about 50% of the time.

Using the above example – where the fridge draws 2.5 amps when the compressor is on, but only runs for 1/2 the day – it will use 30 amp hours of the battery capacity.

Measuring a Fridge’s Power Consumption

Power consumption is measured in Amps per Hour (Aph or a/h), which refers to the number of amps an appliance uses in one hour of use.

There are 2 ways that a/h is measured for camping fridges:

  1. Usage draw – this is the amount of power the fridge draws while running
  2. Average draw – this is the amount of power the fridge draws per hour over a 24-hour period

When determining power consumption, it is important to look at both figures. However, the second figure (average draw), will give the best indication of fridge efficiency.

Fridges will cycle on and off to maintain temperature. Better insulation means less cycling, in turn resulting in a better average current draw.

Dual battery system under car hoodDo not run your fridge off your main battery. Run a dual battery setup instead. Image: Aaron Schubert

What Battery Should a Fridge Run Off?

Fridges should never run off the cranking battery that you use to start your vehicle. The only exception to this is while you are driving, and only if you absolutely must. The reason behind this is simple: your cranking battery is imperative to start your vehicle, so if you run it flat you’ll be in serious trouble.

The most common way to run a fridge is with a second battery, which is isolated from the main cranking battery. The best option is a deep-cycle battery, designed (as the name suggests) to cycle from full to half empty, and back again – anywhere from 1200-1700 times. You can run them off a normal cranking battery, though they don’t like to be cycled and you will shorten its life substantially. Lithium batteries are also becoming more popular, as they have several advantages, but they also come at a pretty hefty cost.

How Low Can I Go With the Battery?

Far too many people think that just because their fridge is running, the battery has enough power left. This is not the case – you should not run your battery to below 50% of charge (normally around 12.2-12.3 volts).

A fridge will continue to run well below this until the low-level alarm is set off and cuts the power. Most fridges have a low-level cut-out, but it’s not usually until well under 12 volts. If you run your battery below 50% of charge, its lifespan will be rapidly decreased – and batteries aren’t cheap!

If you have a 100Ah deep-cycle battery, you should only be using 50 amps of its capacity. This, in the above scenario, is only 1 and 2/3 of a day (without any other consumption) before you start to damage your battery.

From that point on, you either need to start your vehicle and allow the alternator to charge the battery, or arrange some solar input. However, after a couple of cloudy days things start to get a bit desperate! Using your vehicle’s engine to charge the battery is a pretty uneconomical way to do things too.

So – how can you reduce the energy consumption from your 12V fridge? Well, in a similar way to keeping ice cold for longer in an ice box, actually!

A man reaching into his Dometic fridge in the back of his vehicle.You should not run your battery to below 50% of charge. Image: Dometic

1. Cool Your Items Before Leaving Home

Most fridges will have the ability to run on 240V (this is a feature to look for when buying a fridge). If you can avoid it, don’t put room temperature items in your fridge. It will only have it working harder and using more power. Run the fridge on 240V and cool it down at home before heading off on your trip. Most power will be drawn while cooling down the interior of the fridge, so use 240V at home to lower temperature before putting the fridge on 12V.

Obviously, this is unavoidable if you are on the road. Where possible though, pre-chill your food and drink.

2. Crack the Lid Slowly

If you unlatch your fridge and yank the lid up, the rapid movement draws a huge volume of cold air out of your fridge and sends it into the atmosphere. Once you close the lid, the fridge needs to cool down the hot air you’ve just filled it with.

The trick is simple: crack the lid gently until it’s open about 10cm, then open it normally. This will both stop most of the cold air escaping, and save you some substantial power consumption.

A man peeking into his fridge in the back of his vehicle. Crack the lid gently until it’s open about 10cm, then open it normally. Image: Engel

3. Keep the Fridge Full

A full fridge works much more efficiently than an empty one. If you are running low on food and drinks in the fridge, bottles of water work very well. Once they are cool, you’ll save a lot of energy; they don’t immediately change temperature like air does when the lid is opened.

Make sure the food and drink you put into your camping fridge are already cold. If you put a warm slab of drinks into the fridge, it will use lots of power to cool those drinks down to temperature, before it starts cycling again.

Another recommendation is to allow your fridge to freeze (-15 degrees) and add a couple of freezer bricks. Make sure to put the fridge on a few days in advance for it to freeze properly. This will ensure the interior of your fridge is nice and cold. If you have enough space to fit your food in with the freezer bricks, leave one or two in when you pack your food before adjusting = the temperature of the fridge back to two degrees. The fridge will work like an Esky for the first part of your trip, and may not even turn itself on to keep cold for days!

4. Keep Your Fridge as Cool as Possible

It sounds like common sense, but many fridges have been seen laying around in the sun at campsites. Obviously, your fridge will work better in the shade, and out of hot vehicles. If it’s packed in the boot and your car is in the sun, your fridge will be combatting high ambient temperatures and will likely drain your battery twice as fast.

The difference between a fridge operating in an ambient temperature of 25 to 40 degrees is huge. The hotter the air outside of the fridge, the harder your compressor has to work. Obviously, you can’t always the ambient temperature, but you can control where your fridge is stored.

Parking under a tree, for example, will keep your vehicle much cooler and reduce how much work the fridge has to do to keep your food and drinks cold. If you are parked up, open the back of the vehicle so it doesn’t heat up.

A couple are loading a crate of food into a portable fridge.

A full fridge works much more efficiently than an empty one. Image: Dometic

EvaKool 55L fridge in back of Nissan Patrol

A fridge slide is a good way of keeping your fridge secure in the 4WD, but popping it out like this, when you’re at camp, ensures airflow. Image: Aaron Schubert 

5. Airflow is Imperative

The compressor in your fridge will produce heat, a by-product of reducing the temperature inside the cabinet. It’s important to allow plenty of space for this heat to escape from your fridge. More ventilation results in better efficiency. It’s all well and good having your fridge packed in tight – but if it can’t breathe freely, you are making it work hard. Ensure the compressor has ample room to suck in clean, cool air. If you have the fridge mounted in an enclosed area, consider the use of a  small vent or computer fan to aid air circulation.

Toolboxes on the front of camper trailers are popular for mounting fridges, but on a warm day they can easily reach 65 degrees inside. While it probably won’t kill your fridge, it isn’t doing it any favours in terms of longevity – and will most certainly cause it to consume more power.

6. Fridge Covers

You’ll see that a lot of fridge manufacturers sell covers for their fridges. These help to protect the fridge, but also improve their insulation properties. The better insulated your fridge, the less heat that can pass through and the less cold air that can escape. Almost all fridges will benefit from an insulative cover by preventing the outer casing from heating up. It’s kind-of like putting an Esky into a soft cooler bag. By adding extra insulation to the fridge, it will stay colder for longer and thus use less power.

Next time you are at your fridge, touch the outside of it when it’s running. If it is noticeably cooler than the air around you, the insulation is allowing the cold to escape.

Waeco fridge cover

Fridge covers help insulate the fridge so that it runs cooler. Image: Aaron Schubert

7. Time and Number of Times Opened

The longer you leave your fridge open, the more it has to cool down when you close it again. Every time you open the fridge, you will displace the cold air. This means the fridge has to cool all the new air that has entered the fridge.  Limit the amount of time the fridge is left open or how frequently it is opened to prevent the internal temperature rising. Make a habit of grabbing what you need quickly and closing the lid. 

If you are about to cook something, have a think about what you need before opening the fridge. Don’t limit yourself to only opening the fridge a few times a day, but anything you can do to limit the number of times you open the fridge is ideal. As mentioned in the blog post on keeping ice from melting, perhaps have a small icebox at your disposal to keep drinks nearby. This will save you from having to open the fridge too often.

8. Close the Lid Properly

While it’s easy to just drop the lid and not do up the latches, if any air can pass in or out it’ll have the fridge working harder. Take the extra two seconds to latch it closed.

EvaKool Fridge secured on the back of the 4WDSnowys blogger Aaron Schubert’s trusty EvaKool 12V fridge. Image: Aaron Schubert.

9. Check the Wiring

The power supply to your fridge needs to have adequately sized wiring. If it is too small, you’ll lose efficiency quite quickly. Usually, this is an issue from your battery to the fridge power-point, especially if it’s running from the front of the vehicle to the rear. It’s recommended to run a 6mm square cable, minimum. 

Heavy-duty wiring from your 12V battery to your fridge won’t have your fridge use any less power, but it will help you get more out of your battery. Many standard vehicle setups have thin wiring looms that attribute to voltage drop. This means that while your battery reads 12.5V, only 12V is reaching your fridge. Furthermore, if your fridge is fitted with battery protection, it may turn itself off despite there being plenty of life left in your battery.

10. Use a Quality Fridge

Lastly, if you’ve bought yourself a cheap fridge and you find it’s chewing the power, it might be time to consider upgrading to a more quality unit. Brands like Engel, Dometic, Evakool, and Bushman have each earned themselves a solid reputation!

Keeping an eye on the battery voltageKeep an eye on your voltage usage. Image: Aaron Schubert

Enjoy Your Fridge!

There’s nothing quite like being able to pull a cold drink from your fridge in the middle of nowhere. Enjoy the luxury, do what you can to conserve energy consumption – and if it’s still using too much, consider looking at improving your solar or battery arrangement.

A group of friends sitting at a campsite with a drink in their hands, laughing.

There’s nothing quite like being able to pull a cold drink from your fridge in the middle of nowhere. Image: Dometic

This blog is a consolidation of a 2016 work by Aaron Schubert and a 2015 work by David Leslie, updated for 2024.

What sort of 12V fridge do you use? Let us know in the comments.