Woken up to a warm fridge? Sizing your battery system to ensure you're not left with warm beers is an art form.
When you're camping or travelling off-grid, no one wants to wake up to a warm fridge. It means a day of chasing your tail trying to work out how to wake up a flat battery and get it charged before the sun sets again - not how anyone wants to spend their long awaited camping trip.
So, how do you know you have enough power in your battery bank to go the distance?
KEY TAKEAWAYS
- ⚡ Fridge power use varies massively: There's no one-size-fits-all answer
- ⚡ Battery sizing should cover two full days with zero inputs: To allow for cloudy/no driving days
- ⚡ Using an inverter significantly increases daily consumption: It's important to think about everything you take that uses power
How Much Power Does a 12V Fridge Use?
What size battery you need for a camping fridge is a "how long's a piece of string" type question. There's no foolproof answer to this, as how much power your fridge will consume is highly dependent on a LOT of different factors.
There's no substitute for real-world use, but (using a bit of math & decades of experience) there are some "go to" sizes for popular fridge types that we tend to start with.
| Fridge | Fridge/Freezer | approx. 24 Hr Power Usage (Ah) |
|
| 40L |  |
Fridge | 20 |
| Freezer | 30 | ||
| 50L |  |
Fridge | 30 |
| Freezer | 40 | ||
| 75L Dual Zone |
 |
Fridge/Freezer | 40-55 |
| 90L Dual Zone |
 |
Fridge/Freezer | 50-65 |
| 65L Upright |  |
Fridge/Freezer | 30-35 |
| 85L Upright |  |
Fridge/Freezer | 35-40 |
| 135L Upright |  |
Fridge/Freezer | 40-50 |
How to Calculate the Right Battery Size
Now you have a starting point for how much power your fridge will typically consume, the next step is to determine the battery bank size you need. We recommend allowing for 2 days of power with zero inputs (for those non-driving or cloudy days) with a draw down of 80% (assuming a lithium battery). .
So, if we take the 65L upright fridge as an example, we would expect to consume about 70Ah over two days. If this accounts for 80% of your battery bank, you divide the 70Ah by 80, then multiply by 100, which equates to 87.5Ah. In this case, if you were running nothing else (no lights, no charging of phones) then a 100Ah lithium battery would be a good starting point (with some room to spare).
If, on the other hand, you're taking an extended trip and running an upright 80L as a fridge, and also a 95L dual zone for your frozen food, you'll need close to a 300ah lithium battery to ensure your meals don't melt!
What If You're Running an Inverter?
The same principle of two days usage drawing down 80% still applies. You can check here to see how to calculate how much power your inverter will use to run various appliances, otherwise here are some examples of common uses with typical appliances/devices that can run from a 2000W Inverter:
| Appliance/Device | Use | Ah |
| Toaster (900w) | per 2 slices | 5 |
| Pod Machine | per cup | 2 |
| Kettle (2000w) | per boil | 8 |
| LED Light Strip (AllSpark 90cm) | per hour at 100% | 1 |
| Mobile phone recharge | per phone 0-100% | 3 |
| Induction cook top (2000w) | 10 min | 30 |
| Laptop | 60 min (charging) | 6 |
| TV (40W) | 60 min | 3.5 |
| AllSpark Jump Starter | per charge 0-100% | 4 |
Again, these numbers are highly variable depending on the appliance/device, but they can serve as a "rule of thumb" for working out a starting point for sizing a battery bank.
Conclusion
There's a lot of factors which will effect how much power your fridge and appliances use, and you can view some tips for reducing off-grid power usage over here, but the information in this article can serve as a guide to get you started, and to give some insight into whether your system is performing as it should, or if it's way off and another issue besides sizing could be at play.