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Disadvantages of Pure Sine Wave Inverter

DISCLAIMER: AS AN AMAZON ASSOCIATE I EARN FROM QUALIFYING PURCHASES. THIS POST CONTAINS AFFILIATE LINKS THAT WILL REWARD ME MONETARILY OR OTHERWISE WHEN YOU USE THEM TO MAKE QUALIFYING PURCHASES. FOR MORE INFORMATION, PLEASE READ MY EARNINGS DISCLAIMER.

The primary disadvantage of a pure sine wave inverter over a modified sine wave inverter is the cost. This difference is quite substantial! If you are not powering sensitive electronic equipment or don’t mind a buzzing sound, a pure sine wave inverter is probably not necessary in this situation.

An inverter’s main purpose is to convert DC (Direct Current) power from a battery bank or solar panels to AC (Alternating Current) power, which is needed by most appliances. When it comes to powering critical devices such as microwave ovens, game consoles, laser printers, compressors (in the remote area or as a backup solution), Pure Sine Wave inverters are favored over Modified Sine Wave inverters.

This is because the output voltage produced by these extremely useful devices is exactly the same as the utility-supplied electricity (meaning, it has incredibly low harmonic distortion). So, what are the disadvantages of Pure Sine Wave inverters (or PSW)?

#1. Cost

Pure Sine Wave inverters are generally more costly than Modified Sine Wave inverters. A lot more! This is because the components and the technology used in the PSW inverter are quite expensive. Modified Sine Wave inverters are a very popular alternative because of this.

The biggest advantage of using a Modified Sine Wave inverter is the lower initial cost. Pure Sine Wave inverters used to be a more expensive (high-end) alternative for many users, but as the cost of Pure Sine Wave inverters continues to fall, and they are becoming more and more affordable.

Here is the difference in cost between Modified Sine Wave inverters and Pure Sine Wave inverters:

  • Modified Sine Wave inverters range in price from $50 to $600.
  • Pure Sine Wave inverters range in price from $150 to $900.

Pure Sine Inverters are also more expensive per watt than Modified Sine Wave inverters since the equipment they use to produce energy is more advanced. A PSW inverter would cost far more than an MSW inverter of the same wattage.

#2. Power usage

MSW inverters are more economical than PSW inverters. Pure Sine Wave inverters overall use DC power less efficiently than Modified Sine Wave inverters and your battery will discharge faster.

That is due to the complex circuitry of PSW inverters that consume some of the battery voltage. That’s the major drawback of PSW inverters.

#3. Weight

Other disadvantages may include the weight of the PSW inverters. Pure Sine Wave inverters are generally heavier than Modified Sine Wave inverters because of a heavy, inefficient transformer inside the PSW inverter.

You certainly don’t need a Pure Sine Wave inverter if your electronic devices use rectifiers to convert AC to DC. Some laptops can operate without batteries, but the power supply (charger) provides a DC current rather than an AC current to the device.

Past the power source, there is no Sine Wave or Modified sine wave. To put it another way, you only really need a Pure Sine Wave inverter if your devices are:

  • Electronics that contain AC motors (or inductive loads). Example: refrigerators
  • Medical equipment. Ex: If you use a CPAP system, particularly one with a heated humidifier, you should use a Pure Sine Wave inverter to avoid causing damage to the machine.
  • Sensitive to voltage fluctuations electronics. Ex: computers, some laptops, laser photocopiers, printers, hard drives, etc.
  • Fluorescent lights and dimmers.
  • Anything with variable-speed control.
  • Any “intelligent” or “smart” devices.
  • Anything microprocessor-controlled
  • Capacitive input-powered gadgets (flashlights, smoke detectors, etc.) that do not use transformers.
  • Toasters, shavers, hair straighteners, automatic toothbrushes, and other electrical gadgets with microelectronics

** Very important! This list is just an example. Please consult your inverter and appliance manufacturer for more information.

Microwave ovens can work with MSC, but they have a tendency to make noise:

When is PSW (or Pure Sine Wave inverter) necessary?

If you’re going to be wired to the grid, you’ll need a Pure Sine Wave inverter. The reason for this is that utilities supply energy in the sinusoidal waveform. You can certainly use a Modified Sine Wave inverter to power your basic appliances if you’re living off the grid.

Newer LED TVs, CFL light bulbs, and inductive loads like brushless motors all need PSW. Electronics that use motors (such as compressors, refrigerators, microwaves, etc.) usually benefit from using Pure Sine Wave inverter.

They will work on MSW (Modified Sine Wave), but they won’t work as well as on Pure Sine Wave. Using a Modified Sine Wave inverter might lead to excessive heat accumulation and a possible injury.

It’s also a smart idea to review the manufacturer’s recommendation before choosing an inverter typer for your application. Most manufacturers of CPAP suggest using a Pure Sine Wave inverter.

When PSW (or Pure Sine Wave) inverter is NOT necessary

You can’t go wrong with a Pure Sine Wave inverter if you have the resources and are willing to pay more for additional peace of mind. Also, if you don’t have a desire for one, it’s understandable, since most electronic gadgets will work perfectly well with a modified sine wave.

Laptop computers, mobile phone chargers, and any other system that uses a rectifier or AC/DC converter will normally operate well without a Pure Sine Wave inverter. Simple devices with no sensitive circuitry or speakers (that could emit a hum) can easily use a Modified Sine Wave inverter with no problem.

When a Modified Sine Wave inverter can be used

Modified Sine Wave is normally safe for old tube TVs and brushless engines. Digital clocks will most likely behave strangely, battery rechargers can fail.

The main problem with Modified Sine Wave inverters that machinery and different mechanical equipment may operate hotter than usual, therefore shortening its life. MSW inverters can also cause harmonic distortions that affect the normal operation of certain appliances.

If you’re thinking of purchasing a Modified Sine Wave inverter to save some money, think twice. On this waveform, a vast variety of appliances would perform poorly, if at all.

When a Modified Sine Wave inverter cannot be used

With Modified Sine Wave inverters motors have a tendency to work hotter (which means, less effective, wasting up to 30% more energy than with Pure Sine Wave inverters). They will certainly not last as long because the overall harmonic distortion is greater. Consider NOT using the following types of equipment with an MSW inverter:

  • Devices with silicon-controlled rectifiers (ex: controls of some washing machines).
  • Laser printers, photocopiers, and anything with an electrical part called a thyristor
  • Fluorescent lamps with electric ballasts
  • cordless tool battery chargers
  • Modern furnaces and appliances with controls by microprocessors
  • Medical equipment (ex: oxygen concentrators, CPAP, etc.)

Additionally, audio equipment, and other appliances (such as microwaves and ceiling fans), can often emit a buzzing sound if you are using a Modified Sine Wave inverter. Some monitors will have interference such as lines or hum as well.

If you have any doubts about any appliance, tool, or system, particularly medical equipment, please contact the manufacturer to ensure compatibility with a Modified Sine Wave inverter.

Advantages of Pure Sine Wave inverters

Pure Sine Wave inverters have some advantages over Modified Sine Wave inverters:

  • The output wave has a sinusoidal form, which is similar to that provided by a utility company, and low harmonic distortion in the signal.
  • Inductive loads and engines operate more quickly, quietly, and efficiently.
  • Electronic devices produce less audible noise.
  • Prevents computer errors and monitor display problems.
  • Power most electronic devices reliably, with some of them being completely incompatible with Modified Sine Wave inverters

Pure Sine Wave inverters generate a stronger and cleaner current than Modified Sine Wave inverters. On the minus side, they are significantly more costly.

Pure Sine Wave inverters vs Modified Sine Wave inverters

Power inverters are versatile machines that let you survive comfortably on a yacht, RV, or simply living off the grid.  They transform DC voltage into AC (Alternating Current) that most appliances use.

When your home or business starts lacking electricity due to a apower outage, a power inverter (with a battery bank) can be used instead of a noisy generator.

One of the most important considerations when purchasing an inverter is whether to purchase a Pure Sine Wave or a Modified Sine Wave inverter.

Pure Sine Wave (also known as True Sine Wave) and Modified  Sine Wave are the two most common inverter varieties (aka Modified    Square Wave).

Pure Sine Wave (also known as True Sine Wave) inverters produce a sinusoidal waveform identical to the grid’s AC voltage. This is what it looks like:

Modified Sine Wave (MSW) inverters provide a waveform that looks like steps:

The biggest drawback of PSW inverters is that they are more expensive than MSW inverters. It may be a good idea to purchase a small-size Pure Sine Wave inverter to handle your most sensitive equipment, as well as a large-size Modified Sine Wave inverter to deal with the rest of your appliances.

If you only need to power a few basic appliances and are not worried about reliability, Modified Sine Wave inverters are the way to go. However, if you want the assurance that your appliances and equipment can operate safely and efficiently, investing in a Pure Sine Wave inverter is a good idea.


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