Small Quiet Portable Generators

The New Breed of Inverter Generators

Modern motors and modern electronics have made generators smaller, quieter, and more efficient than ever before.

There is nothing new about petrol (or diesel or natural gas or propane) powered generators, but these days we’ve noticed several positive developments – some of these being obvious and some more subtle.

The obvious development is there are a growing number of smaller sized units that are “man portable” – you can easily pick them up with one hand and carry them to wherever you wish to use them.

The more subtle development is these are quiet.  Very quiet.  You’ve probably come across generators in the past somewhere, and will remember them as being noisy loud things.  This is unsurprising, because most of them have only the most primitive of mufflers on them – more a sort of inline baffle than a proper muffler.  Proper mufflers take up more space, soak up some of the output power, and cost more money, so in the past, for “industrial” use, they have seldom been considered as an essential feature.

The most subtle feature is the new breed of generators create “good quality” and “clean” power that you can safely use to power your electronics.  By this we mean that the sine-wave form of the AC power is relatively smooth and unvarying in shape, and the frequency and voltage does not change much as the generator transitions from low loads to high loads.  Earlier generators could sometimes have very imprecisely regulated AC power, and although they were called a generator, they actually used an alternator to create their AC power.  The alternator required the motor to be spinning at 3600 rpm, but as loads varied, the motor might slow down, which would see both the frequency and the voltage drop.

Modern small generators also have an alternator, but the power from the alternator is then converted to DC power, then converted from the DC power back to AC power.  This removes a dependency on the motor’s steady speed, and the electronic (rather than mechanical) conversion of the DC power to AC power includes voltage and frequency regulation that keeps the AC power stable over a broader range of power and operating conditions, with the net result being a much better formed sine-wave and stable voltage/frequency for the output power.

The rather rough and ready power provided by traditional generators was sufficient to run normal lighting and heating and some AC motors, but was very risky for electronics.  The new inverted power can safely be used, even by sensitive electronics.

Interestingly and surprisingly, although they might seem less efficient due to three steps rather than one between having a spinning motor and getting electricity, they actually end up as more efficient – more kWhr of power per gallon of gas.  While the three stage power creation does lose a little bit of the original power from the motor, the motor itself can be operated more efficiently and the gain in motor efficiency more than compensates for a slight loss in power conversion.

The improved efficiency creates a lovely virtuous flow of benefits.  Motors don’t need to be so large, and so are not so noisy, and being more fuel efficient don’t need such large fuel tanks, which makes it easier to create much smaller, lighter and quieter units.

But you know it can’t all be good, don’t you.  There is one slight disadvantage, and we’re not sure how much of this is real and how much is a marketing decision.  Whatever the reason, inverter based generators tend to be appreciably more expensive, in terms of what you pay for a given amount of power output, than regular generators.

But in return for a bit more money, you now have a portable generator you can conveniently carry, put in your car and take with you, for example, for a picnic or when camping, a generator that is sufficiently quiet as not to upset people nearby (and not to upset yourselves, either!), and a generator that will run for maybe half a dozen hours on a single gallon of gas.

What to Look For in an Inverter Generator

Generally most of the inverter generators tend to provide about 1600 – 2000 watts of continuous power and maybe about 20% more than that for brief surges, such as when you have motorized things starting up and drawing more power during the start phase of their operation.

They tend to weigh about 45 – 55lbs.  They will have about a one gallon gas tank, and usually are driven by a four-stroke engine.  Their noise will usually be somewhere in the mid-50s of decibels.  They are manual pull-start units.  Their price probably ranges somewhere from the mid/high $300s up to about $600, but some “name brand” outliers might cost twice that much.

Amazon currently shows 84 units, with the lowest priced units being just under $390 and providing about 2,000 watts of peak power and 1,700 watts of continuous power.  The most expensive inverter units that still have some credible claim to being portable are about $1150 and offer about 3,500 watts of peak power and 3,000 watts of continuous power.

Although it is not always obvious, many generators seem to share the same motors – and, for all we know, the same electronics too.  We’d probably be willing to pay a bit more for a “name brand” motor that we recognized, rather than a nameless generic Chinese motor, although we wonder if even Japanese motors aren’t often made in China these days.  If they are, hopefully they have been better designed and better quality controlled than 100% designed and built Chinese motors.

We note the most expensive units are Honda units.  We think you’re paying an unjustifiable premium for the Honda brand – they can be almost three times as expensive as other more generic units.  Better to buy two less-well known brand units and have spare money left over than to buy one Honda unit.

Let’s now look at the distinguishing features and “must have” features of a portable generator.

Important and Desirable Features

The key attribute of a generator is how much power it generates.  But that’s a slightly subjective number.  Let’s look at that and other important attributes.

Power Capacity 

Be careful when comparing generator power capacities.  All generators should advise you two different numbers – one being the maximum number of watts the generator can provide on a continuous basis, and the other being the maximum number of peak watts it can provide for a short period of time – typically 30 seconds or less.

The trap of course is comparing one generator’s peak power with another generator’s continuous power and creating a mistaken impression about their respective capacities.

In terms of power, you can see our earlier article on calculating your power needs to decide how much generator power you want – and are prepared to pay for.  Probably you’ll find you want a lot more power than you’re willing to pay for!  So you’ll need to compromise on this point, and all we can really say is to get as much power as you can afford, and you’ll appreciate all of it.  See also, further below, our point about paralleling two units together for twice the power.

Be aware that you might not always get the full “nameplate power rating” you have been promised.  Most motors have their power output rated on the assumption it is 60°F (15°C) and at sea level.  If you are anywhere higher or hotter, the air becomes less dense and so most motors will not develop as much power.  The impact of hotter weather is relatively minor – about a 1% power loss for every 10°F/5.5°C, but the impact of altitude is much more significant.  Generally the rule of thumb is a 3.5% power loss for every 1,000 ft of altitude.  So if you’re at 3,000 ft on a hot day, you could be losing as much as 15% of your promised power generating capacity.

Some motors have an option for you to buy a different diameter carburetor jet/needle which will compensate for a higher altitude.  We’ve seen one motor brand that offers needles for 3,000 – 6,000 ft and for 6,000 – 8,000 ft as well as the standard needle for 0 – 3,000 ft.  If you live up in the mountains, this would be helpful.

Eco Mode

One of the nice things of these new inverter based generators is the motor doesn’t have to run at a constant 3600 rpm.  With a regular alternator based generator, you are burning more gasoline than you need just to keep the motor spun up all the time.

The inverter type generators often have an “Eco mode” switch on them.  This allows the unit to power down to a lower level when it is only providing a small amount of power, and to spin up to provide more power as and when needed.  Some types of appliances are quite happy with that, others (larger sized electric motors such as in fridge/freezers and a/c units) place an immediate very high power drain on the generator and an eco mode wouldn’t work.  Having the option to turn it on and off is a nice way to potentially make your gasoline last even longer.

Noise Level

It goes without saying that the quieter your unit, the better and more desirable it is.  The good news is that most units cite a noise output level in their specifications.

The bad news is there’s no standard method of measuring noise output.  Is it the noise at idle or at full power or somewhere in between?  Is it a dBA weighted or dBC weighted noise level?  How close to the unit is it?  Is it in front of the exhaust, or behind the exhaust?

These issues can massively change the noise value reading.  If there are numbers being quoted, see if you can understand how they were measured so you can try and compare different claims.

Noise level ratings hopefully are consistent within one manufacturer’s product range though, so if you’re trying to choose which model from one manufacturer, then you can probably use the noise levels as comparative values within their own range.

In general, the lower the number, the quieter.  A 3dB difference in sound is about the smallest difference in volume that most people can perceive, so don’t stress a dB or two of difference, but 10dB of difference is appreciable.

Plugs and Voltages

Different units might offer you different types of receptacles and power output options.

The best case scenario is a unit that offers you 120V AC in a couple of different plug options, 12V DC and 5V DC.

 

120V AC :  For flexibility, it would be nice to have a couple of 120V receptacles on the generator.  These should be the slightly different shaped 20A plugs as shown in the image above- you can fit regular 15A plugs into them, and also the slightly different 20A plugs.  If the unit is higher powered, a third and heavier duty 30A socket might be useful as well.

12V DC :  Some units offer a 12V DC power output.  This can be used to power typical 12V automotive accessories, and also perhaps to recharge a car battery, too.  We’d prefer a unit with a “cigarette lighter” type socket (like shown above), some have different types of connectors.  Be sure to see how many amps the 12V circuit offers, you might quickly use up all the amps it offers.

5V DC :  Some units also have one or more USB style 5V power outlets.  This allows you to charge small portable electronic devices, which is another potential convenience (but not quite so much if it is a cold raining night when you don’t want to be outside!).  If a unit offers 5V USB connectors, check to see how many amps they’ll provide – we’ve seen some with low amp ratings like 1.5A, which makes it a long drawn out struggle to get power into a tablet (they usually like over 2A of charging current).

Four-Stroke vs Two-Stroke

These days almost all of these units are powered by four-stroke motors.  Two-stroke motors are a bit smaller/lighter, and are cheaper to manufacture.  They’re also easier to repair.  But, they are also more maintenance intensive, and usually are noisier too.

On balance, our preference is for four-stroke, but if a generator is only to be used very rarely, if there was a much less costly two-stroke option, we might consider it.

Regulatory Compliance – EPA/CARB

We were tempted to put this in the not-so-important category, and in truth if all you’ll ever do with your generator is run it at home, there’s probably not a lot of risk that some type of inspector will come around, demand to check your generator, and impound it due to lack of compliance.

But if you’re going to a national or state park, for example, it is possible the park authorities will require compliance with either or both of these sets of requirements, and may refuse to allow you to use the unit if it isn’t in compliance.

Size and Weight

Most units are reasonably similar in size and weight, but smaller and lighter is usually better than larger and heavier, so it is helpful to identify the differences in size and weight when deciding which unit to buy.

Warranty

We’ve seen a spread of different warranties offered, ranging up to three years.  Needless to say, longer is much preferable to shorter, and with a wide range of different warranties being offered, this is something worth checking and comparing.

Not so Important Features

There are plenty of other features that might or might not be desirable for you.

Fuel Gauge

It would be a nice bonus to have a unit with a fuel gauge on it.  That is so much nicer than having to unscrew the fuel tank lid and peer inside with a flash-light to try and guess how much fuel is remaining.

Some units have small little gauges, and some have electronic gauges.  As long as the gauge is easy to read and somewhat accurate, it is a definite plus.

Fuel Consumption

Units will generally give you a vague reference to how much fuel they use for how much power they generate, although this is much less “scientific” than a mpg sticker on a car.

Usually the claim seems to be “a tank of fuel will last x hours at 25%/50% power”.  So you need to understand how much fuel the tank holds, and be careful to distinguish between claims based on 25% or 50% power levels.

We don’t rate this as an essential feature however, because it seems you’ll likely be spending less than $1/hour for gasoline on all the units.  When you consider the number of hours a year you’re likely to have your generator running, the difference between 90c/hour or $1.00/hour is not really very important.

Ease of Servicing

This isn’t something you’ll be doing a lot of, hopefully, but most units do recommend an oil change about every 50 hours and a spark plug change maybe every 100 hours.

See how easy it is to access the oil – both to add oil and to drain it.  Also see about spark plug, air filter and muffler access.

Paralleling Two Units Together

A typical portable generator is going to cost in the mid $400s or a bit more, and give you about 2000 watts of power.  A high powered portable generator is going to cost over $1000 and give you about 3000 watts of power.

That is a bit surprising – you’d think that if you paid twice as much money, you’d get more than twice as much power generating rather than less than twice as much.  We don’t know why this is.

While you can do quite a lot with a 2000 watt generator, there are also things you can’t do, and you’ll also have to juggle your power management – “If this is on, I have to turn that off” and so on.  More generating capacity gives you much more flexibility.

You have two other ways to get more generating capacity.  One is to buy a larger standard type of power generator – only semi-portable and without nice clean inverters.  The other, and this might be the best approach for many people, is to buy a pair of smaller 2000 watt generators and couple them up together in parallel.

This is more complicated than it seems (behind the scenes – for you, all you do is plug a special cable into both units), because the two generators have to be synchronized so both their sine waves are rising and falling at the same time.  That is very complicated – close to impossible – with mechanical alternator created power, but it is easy with electronically converted DC to AC power.

What was originally a high end option is now common on most of these generators.  If you want to double your power supply, you simply buy a second generator and a special control/combining cable and plugs (usually cost seems to be about $75 or so) to connect the two together, and you now have a single source of twice as much power.

Look for units that add a higher powered outlet receptacle as part of the connector cable.

Dual-Fuel

Not very commonly found, but a few of the units can run on either propane or regular gasoline.  None offer diesel as an option, because diesel motors are heavier and much more expensive and less amenable to multi-fuel concepts.

We love propane for several reasons and would definitely pay more for a generator that can accept propane.

Propane doesn’t get stale.  Regular petrol does – you need to add fuel stabilizer to the petrol and even so, might have problems when you try and run your generator for the first time in a year or two.  Yes, we know you should run it for a short while every week or month, but few of us do!

(A suggestion in this context – at the bare minimum, why not add running the generator to your list of things to do every half-year when daylight saving starts and stops.  You do have a list like that, don’t you?)

Adding fuel stabilizer is a hassle and an extra cost.

Propane is cleaner burning and probably ends up giving you reduced maintenance issues and better oil life, spark plug life, muffler life, and engine life in general.

There might be fewer storage restrictions on keeping propane in your residence than keeping gasoline.

Propane can also be used to power a barbecue or stove top so you can have cooking as well as electricity from a single emergency power source.

To compare propane and regular gasoline, as a rule of thumb, you can approximately equate the power you’ll get from a 20lb propane tank as being the same as you’d get from 4 gallons of gasoline.

There is one downside of propane.  Usually it seems that when you run a motor on propane, it develops about 10% less power, and so your maximum generator output will drop about 10%.

We’d still prefer propane to petrol if at all possible.  Every petrol-driven motor on any device we’ve ever owned has always given us maintenance challenges, and the last thing we want is a maintenance problem when we go to start up our generator in a power outage.

If you have a regular gasoline powered generator, it is desirable to have one which can allow you to run the carburetor dry – a fuel cut-off switch rather than (or as well as) an electric “on-off” switch that just kills power to the spark plug.  This is a benefit because it means you don’t have gasoline aging and “going off” in your carburetor.  Some generators have fuel cut-off switches, and some allow you to drain the carburetor, most have neither feature.  Carburetor draining is a hassle but perhaps better than nothing.

Unnecessary Features

There’s not a lot of unnecessary extra features we’ve seen on these units, but one certainly sticks out.

Electric Start

This is not a common feature, and it is not something we’d pay extra for.  A few units have the ease and convenience of push-button electric start instead of the hand-cord you have to pull to start the unit.

Because most of the motors are small in size (usually 80 – 120 cc displacement and single cylinder) hand starting them is not too difficult – no worse than a lawn mower, and possibly easier.

Having an electric start means you need to have a starter battery in the portable generator, which makes your unit larger and heavier.  It also adds to the cost, complexity, hassle, and maintenance requirements.  You’ll need some way to keep the battery charged, and from time to time, the battery will need to be replaced – Murphy’s Law pretty much mandates that the time you most need your generator to start will be the time the battery dies on you.

Some Other Thoughts

Please always keep in mind these units must never be used inside.  They output plenty of carbon monoxide, so must not only be kept outside, but make sure the exhaust is facing away from your residence, and consider also having some carbon monoxide detectors in any rooms close to the generator.

When deciding where to site your generator when it is being used, you also want to keep the length of extension cords as short as possible.  You also should use heavier gauge cords than you probably use around the house at present.  We recommend a 12 gauge cord from the unit to wherever in the house you then might have multiple devices plugging in to it.

Due to their not-very-great power capabilities, there’s not a lot of reason to consider wiring a power Transfer Switch into your residence for one of these units.  They are better suited for larger generators, which we’ll discuss in a subsequent article.

If your generator is outside somewhere that is at risk of being stolen, you could get a bicycle chain padlock unit and padlock the unit’s handle to some part of your residence.

We’ve noticed a trend for things that aren’t generators to try and pass themselves off as generators.  These other things might be a “solar generator” or a battery pack, and while they may well store and provide some power, they won’t provide nearly as much power, or for nearly as long, as a gasoline (or propane) powered generator.  Make sure you aren’t fooled by these other types of products.

We recommend you buy a generator before you need one.  As you may have noticed in the past, whenever there is a mass power outage, all the hardware stores empty out of generators almost immediately.  Sometimes they will empty out of generators a few days before, if there is some publicity being given to an upcoming extreme weather event.

Amazon of course is a great source, but we’ve not seen any units in their same day/next day delivery programs, so even they require some patience and forethought.

Summary

A lovely small portable generator can easily fit in your garage or store room, and gives you reassurance the next time your power goes out, and gives you convenience and comfort the next time you go picnicking or camping.

A recommended addition to your collection of goodies.