What Is An Inverter Generator? Pros and Cons (vs Conventional)

You need a generator for your camping, planning a RV trip or perhaps you just need some extra power to supply your appliances? You definitely heard of inverters generators. What are they? How are they better than the “other” generators called conventional?

The main difference between inverter and conventional generators is the presence of an electronic device called an inverter. This allows the engine to rotate at variable speed, emit less noise, working better at variable load, and having higher power quality. Inverter generators are also smaller in size and more expensive.

However, why should you choose an inverter generator and why might it suit you better than a conventional one? Many are the factors to consider and here you have detailed broken them down so you can understand yourself what is better for your specific needs.

How Does a Conventional Generator Work

To better understand what a conventional generator is and how this relates to the inverter version, it is important to understand what a conventional generator is.

Skipping the detail engineering part (more than happy to dig into it if someone wants it), a conventional generator operates in two steps: 1) convert the fuel chemical energy into kinetic energy (movement) to then 2) convert such movement into electricity.

Sounds pretty simple. This is obtained through three components, common to any conventional generator:

1. Fuel tank: this can be external or internal and can host a different type of fuel, often in liquid form;
   
2. Engine: this converts the fuel energy (just burning it) into kinetic energy (movement). If this sounds familiar, this is exactly what your car does. There are crazy YouTubers as the ones that converted an old car engine into an alternator (video below).
   
3. Alternator: This converts the engine kinetic energy (movement) into alternating current (the same type used by your appliances). This happens by connecting the engine (all of this happens in the conventional generator) to the alternator shaft. This puts in rotation a magnet (either natural or created through current) that creates a moving magnetic field. This is the core principle behind any generator and power plant in the entire world. Such movement induces, for laws of physics, current (electricity) in the static part of the machine where you connect the devices you want to feed.

The key technical difference between inverters and conventional generators is the way the alternators need to work to produce “usable” electricity. In conventional generators the engine should rotate at a precise and constant speed independently from the amount and type of appliances/devices connected to it (from a toaster to a heater). This is not the case for inverter ones.

This speed is usually identified as rotation per minute (RPM, for large generators is usually 3600 RPM) and often you can find this number in the generator manual.

When I talk about usability, I mean with a frequency of 60Hz and of a sinusoidal shape (more on this later). If the shaft rotates at a different speed (suppose slower) then the electricity will not be 60Hz. Why is this a problem? Well, this will damage, even permanently most of your appliances.

How Does an Inverter Generator Work?

Inverter generators have an extra device, called “inverter”, that removes the “limitation” of a conventional generator to be forced to rotate at a specific (maximum) speed.

How Does It Work?

Inverter generators follow the same simplified principle of conventional generators. They convert chemical energy into kinetic energy, and ultimately into electricity. They still have a fuel tank (usually smaller and embedded), an engine, and an alternator.

However, rather than giving to your appliances the electricity directly produced by the alternator, they clean and adjust such type of electricity with the inverter.

The Extra Step: AC-AC Inverter

The inverter is an electronic device that converts the current produced by the alternator into usable alternating current for your devices. This happens usually through 2 stages:1) converting first the alternating current of the alternator in direct current (the same of your batteries) and then, such direct current converted in alternating again. However, the alternative current in output is way more suitable for your appliances.

Chatting with some experts, I noticed that it is not impossible to find inverter generators that use an engine-powered direct current generator. This means that the generator produces direct current (yes current has a “shape”, the one you use at home is sinusoidal in shape). In this case, you need only the last stage of the inverter (the DC-AC that converts the current into sinusoidal “shape”). Having one or the other depends on the manufacturer. Indeed, DC generators are more expensive while the inverter is less. However, I more commonly found AC generators within inverter ones.

The key point you need to remember is that these inverter generators also have electronic devices that control the speed of the motor to maintain an equilibrium between the current fed to the appliances connected (to the generator) and the speed of the engine. In other words, and here is the big difference from the conventional generators, the speed of the engine driving the alternator changes while the current in output to feed your appliances is still good for them. This is not the case for the conventional generator. Their engineer needs to rotate at the same speed all the time.

The engine of an inverter generator is going to rotate faster (and louder) when you have lots of appliances (machines) connected to it while way slower (and quieter) when you have few (or none) connected to it. The engine of a conventional generator will run at (for instance) 3600 turns per minute even if you have a tiny toaster connected to it.

As you can notice the inverter generator is way more sophisticated than its conventional counterpart. It has electronics to change the “shape” of the current (yes, current has a shape) the frequency (60Hz), and maintain the balance between the speed of the engine and the output power.

Inverter Generator vs Conventional: Pros and Cons

I hope you now have a grasp of the technical differences between inverters and conventional generators. What you need to remember is that an inverter goes a step further by having an electronic control of the stability of the power in output.

However, you might now wonder what is best for your use. Well, I cannot give an answer without knowing what your needs or situation are. So, here you have it, a list of pros and cons to let you decide!

Fuel: Gasoline, Diesel, and Propane

Each generator is designed for a specific type of fuel.

Often inverter generators are fuelled with gasoline hosted in the fuel tank embedded in the generator (usually at the top). However, it is not unusual to also find inverter generators fuelled with diesel or propane. However, do not be confused. If you remember the 2 steps mentioned at the beginning, the fuel affects only the engine type.

A diesel engine creates motion by compressing air without ignition compared to a gasoline engine that requires a spark within the cylinder to create the expansion of the air/gasoline mix in the cylinder. This translates into higher efficiency. Moreover, diesel is more energy-dense than gasoline so produces more energy using the same amount of space.

Gasoline generators are fine too of course if diesel is not for you.

Remember, that you can also find a dual fuel generator. It is not uncommon to look for Gasoline and Propane ones. Propane is usually provided by connecting a propane metal tank (containing liquid propane under pressure) to the generator “LPG Inlet” through appropriate cabling.

Conventional generators, similarly to inverter generators, can use gasoline, diesel or propane, or a combination of them (dual generators).

Side note: talking with some friends they mentioned, by accident, bi-fuel generators. These are special types of engines that are designed to switch automatically between two fuels depending on the conditions. As far as I know, this is not a technology used for portable generators but rather for cars.

Hence, in my opinion, the type of fuel is not a factor in deciding if to adopt an inverter or conventional generator.

Power Quality?

This is a hot topic. I found quite a lot of debate on what is better for your appliances or tools. It is very confusing, I got it. I will try to sort this confusion out!

What is the power quality of the current?

Current has a shape. Sinusoidal to be precise. The more sinusoidal it is, the better for your devices. The current has also a speed. This is measured in hertz. In the USA it is 60Hz while in the EU is 50Hz. Hence, to make your life easy, think in this way: the closer the current is to have a sinusoidal shape at a “speed” of 50 Hz the better. A current is polluted if this is not the case. One measure of pollution is the total harmonic distortion. The highest the worst.

Why does the power quality of your generator matter? Some appliances, machines, and equipment might not work properly or even be damaged with “polluted” current.

I had many friends reporting or not being able to use a laptop or other specific equipment with poor quality inverter generators. This applies especially to electronic devices as more sensible too.

An inverter generator, in its last inverter stage “, reconstructs” the DC current into a sinusoidal shape (sinusoidal current). This increases the total harmonic distortion (lower quality). Nevertheless, the majority of inverter generators produce currents of high quality enough. On the other hand, a conventional generator generally produces a way more distorted current.

However, this is not the whole story!

To understand this concept, think about drawing a curve line as a succession of tiny horizontal lines. If you draw millions of tiny straight lines the overall results will be very close to a curve, especially if you look at it not from a short distance. However, if you only draw 2-3 straight horizontal lines, the results will be very poor. You will have a sawtooth appearance.

This is the same identical principle of an inverter. By opening and closing (very quickly) some electronic switches, the inverter regulates the “smoothness” of the sinewave by “drawing” it.

This will create what is called in jargon a sawtooth effect. Inverters are quite good at creating a sine wave (lots of staring lines), but they’re not perfect.

However, nowadays high-quality inverters (that open and close their switches very fast) can be avoided as they will produce a high “resolution” sine wave. As shown in this experiment based on real field measurement, an inverter generator causes a distortion of around 4-5%. This is totally comparable to the quality of the power you receive at home that, in the USA, varies around 6-10% pollution depending on the region, and type of appliances connected to the network.

Conventional generator do not produce a perfect sine wave because of two scientific reasons:

1. Alternator structure imperfect: conventional generators (as inverter ones) have alternators (those that convert movement into electricity) whose mechanical structure, despite being optimized, is still imperfect. Without getting into much engineering (mainly mechanics) details, such alternators present an air gap that naturally varies over time. This creates pollution in the current;
   
2. Electronic problem: when the conventional generator supplies more “complex” devices (mainly electronics) the situation gets even worse. The irregular current that such devices create “go back” to the generator making the power supplied even worse. Don’t you believe me? Well, check by yourself this Westinghouse conventional generator manual. It has a declared current pollution level (THD) of 23%. A 20%+ pollution level is normal for this type of generator.

Is this bad? It is for your laptop or refrigerator, less for large motor-driven tools as they are more robust and less sensitive to such lower quality types of current.

Inverter generators are way better suited to supply home appliances, electronics included, with virtually no risk to damage them. This is not the case with conventional generators that can damage sensitive appliances, especially if also the load is variable.

To be 100% sure check the manual. An inverter generator should have a total harmonic distortion (often abbreviated as THD factor). If this is below 10% (ideally lower than 6%) you should be OK also with your home appliances. If not in the manual just drop a quick email to the manufacturer.

However, do not ditch a conventional generator straightaway. If you need it for heavy tools (cutting or in the working field) that are not electronic, then conventional generators might be your pick. You need to check if what you need to supply can withstand a 20-30% THD.

Nominal Power

The nominal power of an electric generator defines how many appliances can be connected at the same time. The nominal power is measured in Watt (W) and it is often indicated in the branded name of the generator by a 4 digit number (for instance the famous Honda 2200 generator, has a nominal power of 2200 Watt).

Conventional generators have a way larger nominal power than inverter ones. Conventional generators can easily reach 10,000 W or more compared to inverter generators whose size typically does not go above 3,000-4,000 W (you can find larger ones, but they are less common).

If you need a generator camping, your RV or just some appliances in your house can easily get on (and you should) with an inverter generator. Remember, that using a generator way larger than what you need, in general, leads to lower efficiency and so fuel waste.

Transportability

This topic, as you can guess, is quite strongly related to the previous one. Indeed, if you have a larger generator, you can expect to have a bulkier and heavier machine. Higher nominal power generators require large motors that hence will have larger motors, more wiring, and more metal around.

Conventional generators are significantly heavier and larger than inverter generators. They are easily recognizable as their components are built around a sturdy and cube-like metal and colorful frame structure often equipped with wheels (a frame). Inverter generators, usually smaller, weigh less than 40 pounds compared to hundreds of more conventional generators.

Remember, that, in the last years it is not uncommon to see also inverter generators to be built in an open frame structure and, those, tend to be as heavy as their conventional counterpart.

As a rule of thumb, if you are able to lift a portable generator with one hand (and it also comes with a handle) chances are that it is an inverter generator. Conventional generators, on the other hand, present metal frames (here the name open frame) within which you can find the engine, alternators, and other electronic devices. It is quite common for conventional generators to also have wheels and large handles to drag it around.

Check some size and weight below obtained by collecting some data around the web.

Type – Nominal Power (W)	Weight (kg)
Inverter – 1000	13
Inverter – 2200	20
Inverter – 3000	61
Conventional – 6000	44
Conventional – 7000	77

One last note: the market changes tremendously fast. Hence, do not be surprised if there are no hard rules. Indeed, you can find large inverter generators that weigh more than the smallest conventional generators. Just writing this article, I realized that some company like Honda has released a 7000W inverter generator. This is a 200+ pound heavy piece of engineering, way more than a few 4000W conventional generators.

What this tells me is that over time we will see inverter generators taking over the large size of conventional generators, but not vice versa. You will not see conventional open frame generators of 1000-2000 W but will see more and more inverter ones that take over the higher power range.

To summarise, inverter generators are ideal to use on a camping trip or for an RV due to their low weight and transportability. For more stationary applications like working in a site, conventional generators are the best option considering the higher power requirements for such applications.

Multiple Generations at The Same Time

Have you ever wondered if you can connect multiple generators at the same time? Imagine you bought your great 2000W generators and now you realize you just need another 1000W of power. What should you do? Buy a brand new 3000+W generator? Would it not be possible to purchase a cheaper one of 1000W and “somehow” connect in tandem with the previous one of 2000W so you have the(2000+1000) 3000W of power you need?

A parallel connection among generators is the practice of properly cabling two or more generators in order to provide a total power that is the sum of their individual powers.

Inverter generators present specific parallel entrance plugs that, coordinated with a parallel kit, can allow your generators to run in parallel. This kit can be as simple as a cable connecting the two generators with a third plug to be more sophisticated like the Champion one that presents a more bulky receptacle. Having equal generators will make your life easier, however, it is possible to run in parallel generators of different sizes and even brands (like champion and honda in the video below).

On the other hand, running in parallel conventional open frame generators is not that easy. Indeed, due to the lack of an inverter (that makes life easier), the generators to be run in parallel need to be synchronized (in “phase” in technical terms). In simple words, this means that the voltage they produce should have the same shape at the same time (yes voltage can be roughly defined as a moving shape if you are not very familiar with electrician engineering).

How to do that. Well, one of the most commonly used methods is the light bulb technique. Essentially you connect a lamp between the two generators. When the light bulb is off, it means that the generators are in sync. That is the moment to put them in parallel by closing a parallel switch. It is all a question of timing when doing that. It is not a plug and plays as for the inverter generators.

Both conventional and inverter generators can be connected in parallel. However, for inverter generators, this is easier as there are also kits for this purpose. The same does not apply for conventional generators that require more work. However, in a typical application, it is relatively uncommon to need conventional generators in parallel.

Do you know that parallel large generators were very common in submarines? Indeed, before the introduction of nuclear, large diesel generators, connected in parallel due to the large power required, were charging large batteries when emerging and using the battery energy that when moving the submarine when underwater (as in this condition the diesel cannot work as was not possible to get rid of the exhausted gases).

Polluting

There is no mystery to the fact that both conventional and inverter generators pollute. They both have the same identical working idea. They burn fuel (gasoline, diesel, or propane) to move an engine that, in turn, moves an alternator that produces the electricity we enjoy.

For the curious, the combustion process produces carbon monoxide, oxides of nitrogen, and hydrocarbon. These are all toxic and dangerous substances that you do not want to breathe. That’s why any generators using fuel (not battery) must always be placed outdoors.

However, do inverter generators pollute more or less than conventional generators?

Well, to define the same amount we have to have some kind of standard.

Efficiency

This is another hot topic in the generator community and for a good reason! The higher the efficiency the more money you saved!

One generator is more efficient than another when, given the same amount of fuel, it is able to produce more electrical energy (yes kWh, not kW do not be confused) as output. However, quantification is not simple because between fuel consumption (what you pay) and the electricity produced (what you obtain) you have the take into account the efficiency of the engine, the alternator, and also (for the inverter types) the inverter. As this was not enough, you need to take into account also the number and type of appliances you supply, the ambient temperature, and even the amount of oxygen in the air (generators at high altitudes are less efficient!).

Of course, none of the people I talked to did a scientific study to check this and neither did I. However, researchers around the world did, and here is the surprise.

The commercially available generators, both inverter, and conventional open frames have an efficiency that varies between 19 to 27%. This means that, in the best case, only a fifth of the total energy you put as fuel becomes electricity. This is really low. Moreover, at full load, conventional generators slightly outperform inverter generators. However, the opposite is true out of the full load range.

Hence, when would be more convenient to use a conventional generator rather than an inverter one? If the generator is meant to supply a machine/appliance requiring the same amount of energy all the time as in a working field, a conventional generator is a better choice.

However, in the most common cases in which you need to supply a highly variable load (appliances that turn ON and OFF frequently) the inverter generation will save fuel money in the long run.

Cost per Fuel

This is strongly related to efficiency. A more efficient machine will require less gasoline for the same amount of energy produced, so saving you money in the long run.

Inverter generators are in general more fuel-efficient than conventional generators, especially if the appliances/machine you connect do not work all the time at the same power.

However, how much does it cost to fuel an inverter generator? As you can imagine there is not a single answer to this question. The efficiency, as we discussed before, depends on many different factors (even temperature and altitude!).

As a very rough rule of thumb except for around 0.9 gallons of gasoline for 3.2 hours for a 1800W (rated) generator. However, if you drop the power output to a quarter (450W) it will not last 4 times longer (12 hours) but roughly 2 times longer (8 hours).

The above are the specs of the Honda EU2200i, a quite well-known inverter generator among hobbyists and RV passionate.

For a diesel, you can expect around a third more energy for the same amount of fuel. Hence, for a 1800W diesel, I would say roughly 0.6 gallons per hour. Remember, diesel generators, as discussed above, require less fuel per energy produced for mechanical and fuel-related reasons.

Again, these are very rough numbers coming for a few studies and experience, however, they might change depending even on the model of the generator. To understand how much fuel your generator needs, you need

1. Head to the manual of the generator
2. Check for the fuel tank capacity
3. How long it can operate (this is referred at fuel tank)

Noise

Those of you that have owned a conventional generator know very well (probably too well), how noisy a conventional generator can be. In simple words, you might get ear problems and you stand close to it for long.

Inverter generators are way quieter than their conventional counterpart. For this reason, inverter generators are a better option for those of you that plan to use them for camping, RV, or to supply electricity to their houses in case of emergency (if you do not want to keep yourself and your neighbor awake the whole night).

The engine is the source of the noise. The faster the engine is rotating the higher the noise.

Conventional generators are “obliged” to spin at the highest speed, all the time, independently from the load thus making the highest noise at all times. Among experts, these are called “screamer” generators.

On the other hand, inverter generators can afford to have the engine to spin at whatever speed it wants. Why? Because the inverter will adjust the (unsuitable) current in something that works. So, inverter generators will spin slower at lower load, making less noise.

Here some stats on noise actually measured for generators found by hobbyists that took their own measurements (hence no manual here). As you can see conventional generators are way louder. Remember that an increase of 10db equates to a doubling of noise!

Type	Noise Level – Noise Like
2200 W – inverter (Honda)	63 db – full load at 30ft – Restaurant background noise
3500 W – inverter (Predator)	60 db – full load at 23 ft – Restaurant background noise
3500 W – conventional (Coleman)	75 db – full load at 20ft – Vacuum cleaner
9500 W – conventional (Duromax)	80 db – full load at 16ft – Garbage disposal

Affordability

Portable generators are not cheap. Both the conventional ones and the inverter ones can easily be priced over a thousand bucks. Engine, alternator and to finish the inverter are, by far, the three main and more expensive components of a generator.

Inverter generators, for the same amount of power, are more expensive than their conventional counterparts. The more the components, the higher the price. A 5000W inverter generator is way more expensive than its 5000W conventional one.

Another second reason that justifies the price difference is that, in general, inverter generators are smaller in size. Hence, the price per unit of power produced is higher.

Here below, I just scout the web and put together a small table with some prices. You should not use them as a buying guide (I will write detailed ones that analyze bit by bit everything of those generators) as the price can change. This is just to give you a rough idea of how much the price of an inverter generator is higher than its conventional counterpart.

Type	Price (price per 1000W)
Honda – 900W rated – Inverter	$939 (1043$ per 1000W)
Generac – 3000W rated – Inverter	$730 (243$ per 1000W)
WEN – 3750W rated – Conventional	$427 (115$ per 1000W)
Westinghouse – 3600W rated – Conventional	$479 (133$ per 1000W)

Conventional generators can be at least 2 times cheaper than their inverter-based counterparts when the price per 1000W of output power is considered. Of course, this is a rough estimate as there are countless models in the market at the moment. Also, remember that the higher is the size of the generator (either inverter or conventional) lower is the price per unit of power produced.

Inverter or Conventional Generators? The 3 Cases

It has been a long read. Here I tried to put together some of the knowledge of generators both mine and of some friends and colleagues that used this machine either for work and hobby. However, what you might wonder is, where should you invest your money? Inverter type of conventional type.

Three cases in which inverter generators are the way to go option for:

1. Those of you that need to operate the generator relatively close to where you eat/sleep
2. To those that need to supply appliances/machines whose power change quite a bit over time
3. To those that need to move the generator often
4. To those that need to feed “delicate” appliances such as electronic ones

Hence, if you have an RV and you need to supply your appliances, an inverter generator would be my choice (and it is for many people). This is because you are going to live close to the generator and you are not using the appliances at all times in the same manner.

If you are camping, even more, you might decide to go for an inverter generator. These are lighter to transport.

If you are planning to supply electricity to all your home appliances for a short period of time then, considering the variability of the load, the fact that you live nearby the generator, and also the need to supply sensible appliances (electronic ones) I would opt for an inverter type.

If you have a party and need to supply lights and the DJ deck, in this case, a conventional might be ok. The party is loud, the consumption is almost stable the whole night. However, remember to place the generator a dozen feet away.

If you are planning to buy it for your employee to work on a field, then a conventional generator, given its larger size is probably better. Considering also that you might need a most constant source of power.

Takeaways

It was a long read but it was necessary to shed some light on the generator industry. Hence, what should you remember of this article:

1. Inverter generator presents an extra main component: the inverter
2. This allows the engine and alternator to spin at different speed without compromising the quality of the current provided in the output
3. Inverter generator do not present less quality problem in the power provided
4. Inverter generators are lighter as they are smaller in size
5. Inverter generators pollute slightly less than conventional due to their higher efficiency over a large range of power produced
6. Inverters are easier to connect in parallel
7. Inverters are recommended for all those activities that are more “home/camping/RV” oriented while conventional for those working on open field.