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12V Heaters; do they work, and what’s your options?

If you’ve ever wondered if there’s such thing as 12V heaters, we are here to walk you through the options, and limitations behind heating using 12V power and answer any questions you might have.

At home, most people have access to 240V power and you can get a number of heaters that will run off it, using straight electricity from the grid. Its not the most efficient way to heat a house, but it works, and a lot of people do it.

You are much better off with a reverse cycle split system in terms of efficiency for heating a house, but that’s a topic for another day (although still entirely relevant to 12V heater options).

240V fan heater

Can you get 12V heaters?

Can you get 12V heaters?

There are a couple of fully electric 12V heaters on the market, but they are tiny, and designed for a specific task, like defrosting a windscreen, and not for heating a room up. The reason hardly any exist is because of the amount of power required to create any significant heat.

To make enough heat to warm a room up, or even keep a person warm you need a lot of power, and that’s very hard to do using 12V batteries, and the cabling associated with it.

You can get an inverter and with a big enough battery system you could run a normal household electric heater, but it would only be for a very short period before your batteries were flat.

The simple answer is this: if you got a small powered electric heater, it would use a small amount of power, and generate a small amount of heat. A heater that generates a decent amount of heat needs a substantial amount of power, and doing this from 12V is extremely hard. There’s no beating physics!

How much power is needed?

I want to make this as simple, and clear as possible, so I’ll compare running a normal heater at home to doing it off a battery system, using 12V. Please remember that any heater with wattages less than what you’d use at home are generally pretty useless, so if you go for a lower wattage unit, expect a lower amount of heat to be generated.

If we look at a normal household fan heater that you can pick up for under $30, most have two settings; 1kW, and 2kW. To give you an idea, in Perth right now, running one of these on full bore costs you nearly 60 cents an hour in power costs, which is quite a bit (and is often the reason why people end up with massive power bills). 

If you wanted to run a normal household heater off an inverter and battery system, it would pull somewhere between 80 and 180 amps to run the heater on either of its settings. 

A normal, average caravan electrical system running lead acid batteries might have a usable capacity of about 100 amp hours, which means that even if you could run it, the battery would be flat in 30 – 70 minutes. However, there’s another problem, and that is most 12V battery systems can’t be discharged so quickly without doing damage, or faulting out.

Household electric heater

Running a normal 240V household heater off 12V is extremely difficult without a huge system

If you had lithium batteries it might be an option, but you are still going to have flat batteries extremely quickly. Even with our 340 aH of Renogy lithium batteries that we run in our Hybrid Camper, we’d only be able to run the unit on high for under two hours, before the batteries were completely dead, and that’s virtually useless for life in the real world. If you want to know more about our system, we have a post here: Hybrid Camper lithium battery and solar upgrade.

Ultimately, you can’t run an electric heater of any sort when camping without a generator, or a massive battery system. There are however, some other options that are far more suitable for camping, which we go into below.

Renogy upgrade

Even our big battery system isn’t suitable for a normal 240V heater for more than a few hours

All electric heaters use the same amount of energy

Before we go on, I want to point out that it doesn’t matter what type of electric heater you get. They are all extremely heavy consumers, and they are all very similar in their ability to create heat from electricity. Whether you get a bar heater, a fan heater, an oil heater or something else, you are still going to take 1kw of power, and turn it into 1kw of heat.

The energy losses are miniscule in terms of light and fan consumption, and the idea that you can buy a different kind of ‘more efficient’ electric heater is a fallacy. They simply do not exist, unless you go for a reverse cycle aircon, which can do up to 7:1. This means 1kW of power can generate 7kW of heat, simply through their very efficient (but different heating and cooling) setup.

I want to re-iterate this; no electric heater is more efficient than another, unless you go for a reverse cycle aircon.

Alternative camping heaters

The best camping heaters are those that use another fuel source for the bulk of the energy requirements (like diesel or gas) and a small amount of 12V power to run the rest of the heating system. These are the ultimate compromise as you can run them for hours on end without a massive, expensive battery system and still get a serious amount of heat.

Diesel heaters

We run a portable diesel heater in our hybrid camper trailer that uses diesel as its primary source of energy, and a tiny amount of 12V power to get the glow plugs going, and to run the fan. Over night, we might consume 1 – 2L of diesel, and a tiny portion of power, but we get the equivalent heating of 1 – 5 household electric fan heaters running (and we need it, as our camper loses heat very quickly!).

We could comfortably get our camper sitting at 40 degrees if we wanted to with the diesel heater (but prefer to keep it around 13 – 20 degrees!).

If you wanted to permanently mount one (which we’ll be doing shortly), you can read the post we wrote on normal diesel heaters.

Portable diesel heater

Our portable diesel heater in the camper trailer

Gas heaters

Gas heaters are equally as good, and also a common caravan heating option, and once again they use gas as their primary energy source, and a small amount of power to run the heater and push the hot air around. These are quite expensive to have installed, and have to be done by a professional, and you’ll use more gas than diesel, but they are still an option many people are happy with

12V Electric Blanket

The only exception to this, is to run a 12V electric blanket, which due to its design only uses a reasonably small amount of power, and the heat that is generated is used directly onto your skin. These have become quite popular, and are the best fully electric heating option. 

On low, they might draw around 2 amps, and on high around 4 amps (similar to a fridge when cycling on). If you ran a couple overnight on full they’d use a bit of power, but no where near as much as a normal household fan heater!

Inverter reverse cycle aircon

If you really want to stick with power only, the best option is an inverter air conditioner, and a big battery system with lots of solar on the roof to top it up during the day, but this is only really suitable for Caravans with a lot of roof space for panels, and a big budget.

Caravan Airconditioner

If you have a van with a big battery system and lots of solar, an inverter reverse cycle aircon is possible for heating and cooling if you are careful

Want to read more? Here’s our ultimate guide for heating and cooling caravans.

What do you use for heating and cooling? Does it work well? Have you tried any 12V heater options?

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