10 Ways to Reduce Energy Use of a 12V Fridge


A 12V fridge is the ultimate in camping comfort. Menus can be expanded 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’s a lot of focus on solar panels and batteries, but there are a number of things you can do to reduce the energy consumption from your 12V fridge.

How much power does a fridge need?

There are a lot of 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, and the list goes on.

However, most will consume in between 1 amp and 6 amps (with 2.5 amps being fairly average) an hour when running. However, a fridge won’t usually run 100% of the time, so it only pulls that current when the compressor comes on.

Most fridges are loud enough for you to hear them 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.

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 if you absolutely must. The reason behind this is simple – your cranking battery is imperative to start your vehicle, and if you run it flat you can 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, which is 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, but 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 come at a pretty hefty cost.

Dual battery system under car hood

Do not run your fridge off your main battery. Run a dual battery setup instead. 

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 in it. This is not the case – you should not run your battery to below 50% of charge, which is normally around 12.2 – 12.3 volts.

A fridge will continue to run well below this until the low-level alarm goes 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 rapidly be decreased, and batteries aren’t cheap.

If you have a 100amp hour deep cycle battery, you should only be using 50Amps of its capacity, which 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 need to start your vehicle and allow the alternator to charge the battery, or arrange some solar input. However, get a couple of cloudy days and 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.

1. Cool your items before leaving home

If you can avoid it, don’t put room temperature items in your fridge. It only makes it work harder, and use more power. If you are still plugged into 240V this doesn’t really matter, but we normally make a habit of pre-chilling items before putting them in the fridge.

Obviously, if you are on the road this is unavoidable, but where possible, 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 amount of cold air out of your fridge and sends it into the atmosphere. Once you close the lid, the fridge has got to cool down the hot air that you’ve filled it with.

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

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 heap of energy as they don’t immediately change temperature like air does when the lid is open.

4. Keep your fridge as cool as possible

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 only control the ambient temperature so much, but you can control where your fridge is stored.

Parking under a tree, for example, will keep your vehicle much cooler, and reduce the amount of 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.

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. 

5. Airflow is imperative

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 clean, cool air. If you have the fridge mounted in an enclosed area, consider the use of a little 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 get to 65 degrees inside. While it probably won’t kill your fridge, it isn’t doing it any favours in terms of longevity, and most certainly will cause it to consume more power.

6. Fridge covers

You’ll see 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 get in and the less cold air that can get out.

Next time you are at your fridge, touch the outside of it when the fridge is 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. 

7. Time and number of times opened

The longer you leave your fridge open, the more it has to cool down when you shut it again. Make a habit of grabbing what you need quickly and shutting the lid.

If you know you are cooking something up, have a think about what you need before opening the fridge. I’m not saying limit yourself to only opening the fridge a few times a day, that’s silly. But anything you can do to limit the number of times you open the fridge the better.

As mentioned in the blog post on keeping ice from melting, perhaps have a small icebox at your disposal to keep drinks nearby to save you from having to open the fridge too often.

Our Evakool Fridge secured on the back of the 4WD

Our trusty Evakool 12V fridge.

8. Shut the lid properly

While it’s easy just to drop the lid and not do the latches up, if any air can get in or out, it’ll make the fridge work harder. Take the extra 2 seconds to latch it closed.

9. Check the wiring

The power supply to your fridge needs to have adequate sized wiring. If it is too small, you 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 you run 6mm square cable, minimum.

Keeping an eye on the battery voltage

Keep an eye on your voltage usage.

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, Bushman, and myCOOLMAN, have each earned themselves a solid reputation!

Enjoy your fridge

There’s nothing quite like being able to pull a cold drink out of 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/battery arrangement.

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

About the writer...

Joined back in July, 2016

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