Propane fridges give us the fantastic ability to have a working refrigerator even while off-grid. However, one common worry is how efficient (or inefficient!) they are. As someone with an interest in off-grid living, I’ve spent a few hours researching this.
So how efficient are propane refrigerators?
Propane refrigerators are highly efficient. While the efficiency varies per fridge, most last longer than 11 days running non-stop from a standard 20lb propane tank. You can increase this using our efficiency tips below. Still, use electricity when available: it’s cheaper and doesn’t need refilling.
That’s the summary answer, but of course there’s more to it than that.
Read on for more details, tips on how to get the most out of a propane fridge, find how long your propane tank would last, and more.
General Notes
Did you know that absorption fridges (the propane type) were first invented in 1858? A French scientist, Carré, first coined the technology at the Swedish Institute of Technology. Einstein actually proposed his own design – the ‘Einstein refrigerator‘ (a bit confident with that name, wasn’t he?)
Ever since then, the technology has been progressing through innovations until the modern types of propane fridges available today.
Looking to purchase one of these fridges? Check out our detailed run-down of the best propane fridges on the market.
Want to learn about safety? We’ve got that covered too, in our article covering propane fridge safety.
Now regarding their efficiency, there’s not a lot of published data that we can consider for direct comparisons. Especially since they are quite a niche technology. For some rough estimates check out the following sections comparing propane to electricity, and estimating the efficiency from different sizes of propane tanks.
What Affects the Efficiency of a Propane Fridge?
The actual efficiency of a propane fridge will vary slightly depending on conditions, including:
- How hot the air temperature is
- How much airflow is around the refrigerator
- Anything in the refrigerator (ice packs vs. warm food)
- The setup of the refrigerator (i.e. is it completely level?)
Chemical reactions fueled by a heat source. This is either an electric heater, or a propane burner.
How to Increase The Efficiency of a Propane Fridge?
- Switch it on the night before. Will take less time to cool down (lower starting temperature) and be ready for use on the day.
- If you can’t put it on the night before, give it a helping hand by putting a small bag or tray of ice in when you turn it on.
- Make sure it’s completely level. The whole system relies on gravity, so any misalignments will affect the cooling efficiency.
- These fridges don’t have anything to encourage airflow. Picking up a few mini fans can help get the cold air flowing and quickly cooling the fridge.
- Don’t stuff it too full! Leave enough space for there to be good airflow. Particularly when first cooling it down.
- Use electricity to power the fridge before you leave on a trip. Then switch to propane.
- Hodor! Hold the door and keep it shut. Only open it when you need to.
How Does Propane Cool a Fridge?
A propane fridge works using a series of chemical processes involving ammonia, hydrogen, and water. In short, these are:
- A ‘generator’ is powered by burning propane (or an electric heating element)
- Ammonia and water are put into the generator, which seperate as ammonia becomes a gas.
- The ammonia gas is then put through some cooling fins, which cool it back down to a liquid.
- This liquid is then combined with liquid hydrogen in evaporator coils. When they are combined, their reaction produces a lot of cooling. This happens inside the actual fridge.
- Once the reaction is finished, the ammonia and hydrogen are seperator in an ‘absorber’. The ammonia combines with water.
- The ammonia and water go back into the generator. The process starts again!
The whole process. Source.
See a more detailed description in our post covering the best propane fridges (near the bottom of the article).
Using Propane Vs Electricity On A Fridge
Due to the sheer availability, it’s always a better idea to power a propane fridge via electricity – when available. This is simply due to using propane means you’ll need to refill or replace the propane tank. Typically, the difference in energy cost isn’t enough to compare to the time and hassle you lose filling propane tanks.
Directly comparing the costs of both fuel types is difficult: there’s so many variables. Not only their actual costs, but their efficiency in how we use them. We can however draw a basic comparison.
Per this source, if you pay a standard $0.12 per kWh of electricity, and one gallon of propane = 27 kWh of electricity, then 27*0.12 = a break-even point of $3.24. In other words, if you can get propane for less than $3.24 a gallon then you’ll save in comparison to using electricity at $0.12/kWH.
Note: It’s also worth bearing in mind that propane burns cleanly while our electricity is typically generated using fossil fuels, propane is arguably better for the environment (unless we’re talking about electricity from renewable sources.
How Long Will A Propane Refrigerator Run On A Propane Tank?
Let’s work it out together for the example of a standard 20lb propane tank.
- A gallon of Propane provides around 91,000BTU of heat.
- A 20lb propane tank contains 4.7 gallons of propane, or 4.7*91000 = 427,000BTU available
- The average propane fridge uses 1,500BTU per hour to operate.
- 1,500 * 24 = 36,000BTU per day
- BTUAvailable/BTUPerDay= 11.8 days of fuel.
So there we have it. If you’re using a standard 20-lb propane tank, you can expect it to last around 11 days (non-stop) before needing to replace or refill it.
For a 30lb tank just add 50%; so it would last for 17.7 days non-stop.
Note: The above calculations provide a ball-park estimate only. In reality, many propane fridge users find their tanks to last for weeks and weeks. Especially when they’re not in constant use. In most cases, you’ll barely be able to tell a decrease in the level of gas in the tank after a whole day. So I would take these calculations as a ‘worst-case’ estimate.
How Long Will A Propane Refrigerator Run On Battery?
To fully operate a propane fridge on battery can quickly drain the juice from the battery of an RV (or similar). Expect it not last longer than 3 hours. However, if not switched on and only using the electricity for the control panel, this is a tiny amount and can last for weeks.
How Long Does It Take For A Propane Fridge To Get Cold?
As I mentioned above, the answer to this question depends on a lot of variables. Particularly the power of the fridge, and the temperature of the air.
In general, it will take many hours for a propane fridge to cool down. At least 6, more likely 10-12 hours. This is why the best practice is to turn it on the day before you need it, and let it cool down overnight. (This is even more effective given it starts from a cooler temperature at night).
Be sure to reduce the cooling time by following the tips to get the most efficient cooling from earlier in this article.
Conclusion
Propane fridges are an amazing tool to get the advantages of civilization even while totally off-grid. They do come with their disadvantages (upfront cost and long cooling time), but their totally silent, work everywhere advantages are priceless.
I hope this guide has helped give you the information you need to get the most out of your propane refrigerator. If you want to learn more, check out our articles on:
The best propane fridges available
and
I hope you enjoyed this article, and that you have a great day!
-Craig
