Power inverters are electronic devices that change direct current - DC (e.g. 12 Volt) to alternating current (AC), usually at 120 or 220 Volt.
If you live off-the-grid or own a motorhome or a boat, you probably store electricity in your batteries. A power inverter will allow you to use your AC appliances, e.g. a laptop charger, microwave or induction cooker with a power from your battery bank.
There are many types of inverters on the market, and the ones that feature a modified sine wave are less expensive than pure sine wave inverters.
To illustrate, the difference between a modified (square) and pure sine wave of AC current looks roughly like this:
Modified or "quasi-sine" wave inverters can power many of popular appliances you connect to them, such as a laptop charger or a compressor fridge.
However if you want to run modern and more sensitive devices you will likely run into problems. You might experience some electronics run hotter and less efficiently that usual (such as electric motors), some audio equipment will generate an unpleasant buzz, and some appliances might not work at all. Worse still, some devices can get damaged.
Real life example: I connected an electric toothbrush charger to an otherwise well-functioning modified sine wave inverter. It worked for one second, and then it became unusable, even with a pure sine wave inverter.
The conclusion: unless you are certain your devices will work fine with a modified sine inverter, save up some more and invest in a good quality pure sine wave inverter.
Inverters range from very small that can be plugged in your car's cigarette lighter socket, to very big ones that can handle kiloWatts of power. The calculation is simple, just sum up the power requirements of all your AC (120/220V) devices intended to use at the same time.
When changing the DC to AC some energy is lost. Inverters usually have efficiency between 80% and 90% for the more expensive models. You need to take that into account when planning your system, as a 2000W inverter will draw more power from your battery bank than it's designed to output.
While most inverters provide a simple direct to alternate current conversion, others are able to do quite a bit more. For example, some of them come equipped with a charger.
That allows you to charge your batteries from external AC power outlet (e.g. at a camping ground or marina). They might even have the ability to automatically switch between the external power source and your batteries, according to the priority set by you.
Remember about safety features. High power inverters handle big current flows, especially when paired with low voltage battery banks.
For example, a 3000W inverter with 85% efficiency will draw in excess of 3500W when you connect high-power appliances to it. That means currents of 300A and more will be flowing from a 12 Volt battery bank (and 150A from a 24V battery).
This requires seriously thick cables and adequately sized batteries. You will also want to make sure that your inverter has protection systems against overload and overheating as well as features to protect your batteries from too much current being drawn from them.
Below you can find a list of a few high-power inverter models that we know and recommend:
This pure sine wave inverter from Magnum is actually a combo that integrates a 125 Amp charger. This simplifies your off-grid design, as no external battery charger is necessary.
The inverter is of high quality, tested in full-time RV environment. It measures 19 x 15 x 13 inches and weighs around 55 pounds. The unit doesn't include a remote panel, you will need to order one separately.
This highly popular Samlex model packs in 2000 Watts or AC power in a 20.7 x 12 x 6.4 inch format. Pure sine wave inversion ensures operation of sensitive electronics.
Its weight is just over 17 pounds and is one of the quietest inverters available in this power range. Samlex designed it aiming at low levels of interference, so that you shouldn't worry that you radio or television signal gets disrupted.
The Hybrid Series Inverter/Charger from Magnum provides 3000 Watts and offers something what most inverters don't. It can recharge the battery bank when there is extra power available from the AC input, or it can deliver more power to handle the load in case the AC shore power is not enough.
The inverter itself is pure sine, so power your sensitive devices without worry. This inverter + charger combo is covered by Magnum's three-year limited warranty.
Go Power! offers many high quality products and this is one of them. The inverter can supply 3000 Watts of AC power continously, with a whopping 6000 Watt surge if required.
It has several safety features which prevent it from overloading as well as working under inadequate voltage (too low or too high). The unit measures 17.8 x 6.5 x 8.2 inches and weighs 21 pounds. It comes with a 2-year warranty.