12V heaters and kettles are no good

Every now and again, people ask about getting 12V heater, or 12V kettles, or 12V air conditioners, expecting that they are going to be great pieces of equipment. As a general rule, anything that is 12V that heats or cools will perform terribly compared to a proper 240V appliance, and in this post we’re going to explain why, and what you should be looking for.

The purpose of this post is to correct huge expectations that so many people have when they go out and buy a 12V appliance that heats or cools (either for cooking, or for comfort). I want to save you some money by explaining what you should expect (and likely that will stop you making the purchase!).

12V vs 240V kettle comparison

Let’s start with a basic example of heating some water for your morning coffee. You can buy a 12V kettle, and fill it with water, and do the same with a 240V kettle. If you turn them both on, the 240V kettle is going to be about 10 times faster. 

Yes, I’m deadly serious – a 12V kettle will take about 15 – 30 minutes to boil water, and a normal household, 240V kettle about 2 minutes. 

Boiling water takes essentially the same amount of energy whether you do it with 12V or 240V. The difference is that the household kettle uses the electricity over a shorter period as its drawing more power through a higher voltage, and gets a faster result. 

12V kettles pull around 100 watts of electricity. 240V kettles pull about 2000 watts. See the correlation?

There’s a reason hardly anyone uses 12V Kettles today, because they are so slow and the effort is simply not worth the reward. Yes, some people are happy to wait the time, but most people are much happier just putting a normal kettle on a gas stove, or there are quite a few people with lithium battery and inverter setups that will take 12V power and turn it into 240V power to run a normal kettle.

We’ve just recently done a setup like this in our Reconn R2, which you can read about here; Lithium Battery upgrade.

Lithium battery test
Running a 2200W household kettle, pulling 178 amps off our new battery system

Cable sizes

Another reason 12V is not used for high current draw applications is that the cable sizes would need to be far too large, and that’s hard to work with, uneconomical to buy and frankly super inefficient.

The higher the voltage, the smaller cables you get away with. Even if you could get a 12V kettle that was fast, it would have huge cabling as 12V is very low voltage. You could (in theory) get a 2000W 12V kettle, but you’d struggle to plug it in anywhere that would be rated for such an enormous load as the voltage is so low. 

Cable sizing for a DCDC
12V appliances that use a lot of power need huge cable sizes

Heat requires a lot of energy

In simple terms, anything that requires heating is going to use a lot of power. This means kettles, water heaters, air conditioners, air heaters and anything else.

Ironically, if you are using electricity it really doesn’t matter how you do it; the losses are relatively insignificant and whether you use an oil heater, or fan heater, or bar heater the consumption of electricity to create heat is almost identical.

Asides from mild energy losses, there is no difference between using 12V and 240V in terms of actual energy consumed. 12V appliances tend to be much slower and less effective than their 240V counterpart, which uses the energy much quicker.

The only exception to this is reverse cycle aircons, or heat pumps, which are able to operate substantially more efficiently. For example, a normal fan heater running on full bore uses about 2kW (or around 60 cents an hour in Perth), but you can run a reverse cycle aircon that uses 2kW of power and get about 6 – 7kW of heat out of it for the same energy.

You can purchase a variety of 12V heaters, but they are all going to have terrible heat outputs, as you cannot beat physics. Something that uses little electricity will produce little heat, and there’s no way around this.

Jump online and take a look for yourself; the only 12V heaters you’ll find are for defrosting windscreens, and half of them don’t even have enough heating capacity to do this well, let alone actually heat anything up.

Diesel heater
The only exception is a diesel heater, which uses little electricity as the energy comes from the diesel

Consider what 12V appliances you buy

Over the years I’ve been very grateful to gain a greater understanding of power consumption on various appliances. There are plenty of things you can run off 12V with no issues at all, but there are also a huge number of appliances that are a complete waste of money.

If you want to run a 240V appliance off grid there are a myriad of ways that you can go about it (check out How to run 240V appliances when camping), but don’t buy a 12V equivalent and expect it to perform nearly as well as a 240V alternative, as it won’t.

Appliances that run well off 12V

Here’s some of the more common camping accessories, which run really well off a 12V source

  • Fridges and Freezers
  • LED lighting
  • Fans
  • Water pumps
  • Diesel heaters (as the heating energy comes from the diesel)
  • USB chargers
  • Small 240V inverters

The moment you move into induction cooktops, heaters, air conditioners, kettles and water heaters you’ll struggle to find it in a 12V unit, and if you do, its not going to perform well because it physically cannot.

You can still run these appliances with a heavy duty battery system and big inverter, but they are not cheap, and have a huge range of other limitations!

2000W Inverter
With a big inverter and battery system you can run 240V appliances for short periods

Have you experienced any shocking 12V appliances? It’s OK to admit you purchased a 12V kettle and used it once before selling it!

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  1. Hey Pauline,

    You’re very welcome. Yep, induction will be much faster, but probably use similar energy to a 12V kettle (just the latter takes a million times longer).

    Your lithium should easily keep up with the fridge; what solar do you have? I’ve never heard of running pipes on the north side, and would imagine they’d have to be on the roof, or above the awning to be effective (and would hugely increase the chances of leaks).

    If you have a decent amount of solar, you might get away with a Duetto hot water heater, that runs on 12V or 240V, but it needs to be run when the sun is out ideally, so you don’t eat your batteries energy away. Otherwise there are plenty of gas water heater options.

    All the best

  2. Pauline F says:

    Thanks for this – I was considering buying a 12v kettle, but now I’ll give it a big miss!! I did just use the induction cooktop to heat the kettle, and yes, substantially faster than the gas barbecue or cooktop (I don’t want gas inside the van, I’m quite scared of it in enclosed spaces, and I have cats… and cats and flames are not a good mix).

    I’ve got 400AH of lithium and it is an issue right now in winter (not enough sun) and especially on rainy days, to keep the fridge running. (It’s an 80L 12v compressor fridge, I’m still missing living in a house! lol) It’s an education, learning how to make the van run and have life at the same time… I wanted to do solar hot water (pipes on the north side of the van) and still might experiment with that, but I suspect the gas water heater may be an option, once I get the water running in the van. 🙂

  3. Hey James,

    Thanks for the comment. I’m not exactly sure what part of the article that you are referring to, but I did add a minor correction about power draw. The intent was there, but perhaps it wasn’t clear, or you misunderstood it.

    Obviously the voltage stays the same, and different appliances draw different amounts. The primary point of this post was to show that there are virtually no 12V kettles or heaters that are any good, as they all use a tiny amount of power. When you go to 240V you have much more option for running bigger appliances, but they draw a heap of power to do so


  4. Your article is inaccurate when you describe the difference between voltage and current draw. Voltage DOES NOT change, it is amperage that changes depending on demand from the appliance. If you have a 12 volt battery system, it stays 12 volts unless you convert it to a different voltage via a inverter. As an example, your house uses 240 volts and that remains constant but depending on the appliances used, it draws different amounts of energy, that is, Amps, the voltage remains constant at 240 volts.

  5. Hey Marty,

    Cheers, I’m glad you enjoyed it. All electric is possible, but not easy or cheap.

    To be honest, we will probably ditch our kettle; we just use a saucepan on the induction stove, which seems to work fine.

    All the best

  6. Marty Shipton says:

    This is a great article, I’ve just bought a camper trailer, and was shocked that all the vendors were so “pro gas” I kept saying I want all electric and they didn’t get it.
    We did end up with a camper that has gas plumbed in, which we have used, but ultimately that’s because heat pumps and reverse cycle air cons for camping doesn’t exist… yet.
    Induction is definitely on the list, but first I need a 240v kettle, because induction kettles don’t exist…. yet