A 12v inverter is an electrical device that is used to convert direct current (DC) power from a 12-volt battery into alternating current (AC) power that can be used to operate various electronic devices. Inverters are commonly used in a wide range of applications, from powering small appliances in RVs and boats to providing backup power during power outages.

The basic operation of a 12v inverter is relatively simple. When DC power is supplied to the inverter from a 12-volt battery, it is first converted into a high-frequency AC signal by an electronic oscillator. This signal is then sent through a transformer that increases the voltage of the AC signal to the desired level, typically 120 or 240 volts AC.

The output of a 12v inverter can be either a modified sine wave or a pure sine wave. A modified sine wave is a less complex waveform that is suitable for many basic applications, such as powering simple electronics and lighting. A pure sine wave, on the other hand, is a more complex waveform that is designed to closely mimic the waveform of standard household AC power. This makes it suitable for use with more sensitive electronics, such as computers and medical equipment.

In addition to the type of waveform produced, there are several other factors to consider when selecting a 12v inverter. These include the maximum output power rating of the inverter, which determines the maximum amount of power that can be supplied to connected devices. Other important factors include the efficiency of the inverter, which determines how much power is lost during the conversion process, and the number and type of output connections provided by the inverter.

How Much Power Does an Inverter Use?

One of the most important things to note is that no Inverter is 100% efficient. Efficiency means how well or how much DC power is managed to be converted to AC power, it is never a clean 1:1 ration, some of this power is lost due to heat, during the conversion from DC to AC or the auxillary or accessory operations of an inverter (bluetooth control, control panels etc). 

When calculating efficiency I usually use 85-90% as a maximum efficiency operation of the inverter under normal operating conditions. This is fairly standard and what you would generally expect to see in majority of the inverters installed in Caravans. For example I use a 3000W Renogy inverter and it has a maximum 90% efficiency. 

So, how do you calculate how much the load connected to you inverter will use? You’ll need 3 numbers to make this work. 
Lets say you have a 12V system, you’re connecting a power hungry load like a hair dryer that uses 1500W (you’ll be able to find this figure on the specification sticker on the appliance), and we’ll use 85% as our inverters efficiency.
Here’s how that will look 1500/12/0.85 = 147.4 Amps/Ah. So you’ll easily drain a standard 120Ah lithium battery in 45 minutes!
Of course you won’t run a hair dryer off grid for that long, here’s a table below showing the standard AC appliances people take off grid and what power they might consume through an inverter. 

What Size Inverter do I Need?

Choosing the right 12V inverter for your caravan can feel like a daunting task. Have a look at all the AC appliances you are taking with you and find the one with the highest power (W) rating. Take that figure and then consider what other AC appliances you might be running at the same time then simply add all those figures together. If you land at a round number like 1000W, I wouldn’t recommend pairing that up with a 1000W inverter just in case anything runs a bit higher than rated. Give yourself a bit of a buffer and get a 1500W instead. 

For majority of people I think a 2000W Inverter would easily be able to handle your needs, you could probably even get away with a 1000W or 1500W inverter if you have a light set up. However if you are planning on running everything in your van as if you were on a powered site you’ll need at least a 3000W inverter. 

Now you’ll need to make sure your batteries are capable of withstanding the current draw from your new inverter. Check out our post on Lithium batteries and what you should be looking for when running an inverter. 

Conclusion

When selecting a 12v inverter, it is also important to consider the specific needs of your application. For example, if you plan to use the inverter to power a sensitive electronic device, a pure sine wave inverter may be the best choice. On the other hand, if you simply need to power basic lighting and appliances, a less expensive modified sine wave inverter may be sufficient.

Overall, a 12v inverter is a versatile and useful device that can provide a reliable source of AC power in a variety of settings. Whether you need to power a small appliance in your RV or provide backup power during a power outage, a 12v inverter can help ensure that you have the power you need when you need it.
And if you’re planning on being off grid for a while you will need to make sure your solar system can replenish those batteries.

I personally use Renogy products, you can find them here.