A necessary spare tire.
Off grid amateurs have a love-hate relationship with gas engine generators. Due to generators requiring constant refueling and ongoing maintenance, they are not a realistic long-term power solution. Most of them are noisy, many are poorly made, and all of them are dirty. Yet, they are effective, affordable, and can produce a lot of power for their size.
Generators are broken down into three basic types: conventional gas, inverter, and diesel. What is the difference between these? Which is “best”? Do you even need a generator if you already have solar or other off grid energy available? Let’s sort it out.
Our purpose is not to steer you in any one direction. Instead, we’ll go over the different types of generators and offer insight to help make an informed decision.
It’s a mad, mad, mad, mad world!
If you’ve ever done any internet research on generators, you already know there is a lot of information overload floating about. For every person who says generator XYZ is great, there is someone else insisting it’s a pile of junk. All claims, at least on the surface, seem plausible. YouTube alone has perhaps tens of thousands of videos representing every possible generator opinion.
When doing your research, be aware of the intentions of the people from whom you seek information. Many YouTubers and bloggers receive free products in exchange for promotion, or are “affiliates”. Being an affiliate means that the content creator gets paid a cash commission when anyone buys products through a sales code or link associated with their website or channel. In other words, they have a “sugar daddy”. Content creators have a strong motive not to trash-talk about their benefactor’s products!
Even paid shills can be helpful.
This is not to say the advice of compensated reviewers is by default untrustworthy. You certainly can glean a lot of valid information from these folks. They are not necessarily lying, but they are very selective with their truth.
The point is to be very cognizant and read between the lines. Why are they saying what they are saying? What are they not saying? By the way, Off Grid Ham does not have any sponsors or affiliates, and it’s not because I’ve never had offers. Everything on this website is original, transparent observations free of ulterior motives.
Conventional generators: The ageless standard.
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Producing 500-10,000 watts from a small single cylinder engine, conventional generators are easily available at any power tool retailer. They are by far the most popular generator format. These generators operate by rotating a metallic wire loop, called an armature, in a magnetic coil, called a stator. As the loop rotates, current is created.
Each rotation through the north-south poles of the magnetic field produces one complete alternating current cycle. To get 60 cycles per second of AC current, the device would have to turn 60 times per second. That multiplies out 3600 revolutions per minute. Conventional generators must maintain a constant 3600 RPM no matter what the load is, or the frequency will drift off the expected 60 Hz.
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Conventional generators have some significant disadvantages. First, inefficiency. Whipping around at 3600 RPM drinks a lot of fuel. Second, the market is rife with poorly made units. The vibration and high speed is physically stressful and makes the generator prone to mechanical failure. Then there is the noise. These generators are famously loud, so much so that they are appropriately nicknamed “screamers”. YouTube is loaded with advice on how to quiet them down.
Some generators will turn at 1800 RPM. This is achieved by adding a second coil/loop on the armature. The engine is turning at half the speed as a 3600 RPM model, but creates the same number of electrical cycles with each revolution. The end result is a 60 Hz power output. Most 1800 RPM generators are diesel-fueled. Small 1800 RPM gas generators are exceptionally rare.
Conventional generator lifecycle.
How long one can expect a generator to last is highly speculative and depends on the devices’s initial build quality and how it is used. For example, a low-end generator beat to hell daily on a construction site may only last a year or two. If the same generator is treated well and used occasionally for short term power outages, it might last many years. Generator lifecycles are measured in hours of runtime. The less a generator is run the longer its total service life will be.
Higher quality generators can provide decades of reliable service if cared for properly. I have a 30 year old Honda conventional generator that was already 20 years old when I got it. It has probably thousands of hours on it. That old man still starts easily and runs great every time. If I had to replace that generator today it would cost 4-5 times as much as a comparable off brand model.
It’s the age-old question: Should you spend more up front and invest for the long term, or spend less now and spread the expense out over more than one purchase? Each individual will have to make a decision based on their needs and budget. Of course, buy the best if you can. For radio amateurs on a small budget who don’t expect to roll a lot of hours on their generator, it may be financially sensible to buy a low tier machine with the expectation that it is not a lifetime investment.
Inverter generators.
What if anything can be done to avoid living with an obnoxious “screamer” that slurps a lot of fuel and must always turn at 3600 RPM? For the off grid ham, the go-to solution is an inverter generator. Inverter generators turn an alternator just like their conventional brothers. Instead of connecting a load directly to the alternator output, inverter generators add a few extra steps.
The output of the coil/alternator feeds a rectifier, which converts the AC to DC. The DC is then run through an inverter, which creates a 60 Hz AC output from the DC input.
Block diagram of an inverter generator. OFF GRID HAM ORIGINAL GRAPHIC ©2016
If this sounds like a lot of extra complexity to arrive at the same place, well, it is. It’s not for nothing, though. If we dig a little deeper into how inverter generators work, the extra steps make sense.
Inverter generators eliminate the need for the engine to run at 3600 RPM all the time. Instead, it can turn faster or slower according to the load. This makes for quieter, more fuel efficient operation. As the engine changes speed, the frequency of the alternator output will change too, but it does not matter because the rectifier converts it to DC anyway. The inverter will make a nice, clean 60 Hz AC output no matter what the speed of the engine may be.
The extra hardware and circuitry drive up the cost of inverter generators, compared to a similar conventional model. Is it worth it? Again, that’s a personal decision. From an off grid radio operator perspective, other than lower initial cost, conventional generators have almost no advantage over inverters.
Inverter generator lifecycle.
Like the others, inverter generators are available with widely varying build qualities and price points. The Honda EUxxxxi-series is at the top of the pyramid of inverter generators and has a price tag appropriate to its stellar reputation. Lower-tier off brand inverter generators often look a lot like Hondas and can use Honda parts because many of them are knockoff clones.
In terms of build quality and expected service life, do not assume inverter generators are inherently “better” than conventional generators. While it’s true that inverters do not have the same mechanical stresses as conventional models that run at 3600 RPM, all the same caveats and warnings apply.
Basically, there is Honda and there is everything else. If you go with Honda, you have little to worry about. When used & maintained as designed, a Honda will last for decades. If you go with anything else, do your due diligence. There are some great inverter generators out there that are not Hondas. Yamaha makes an outstanding line of inverter generators. The only caution with Yamaha is that in the USA, their service and parts network is not very robust…but then again you’ll not likely need it!
Other considerations.
Gas is the most popular fuel, but there is also propane and natural gas. Many generators come from the factory with bi-fuel or tri-fuel capability. If your gas generator does not have this option, aftermarket conversion kits are easy to find, relatively inexpensive, and can be installed as a DIY project. Even if you don’t think you’ll immediately need it, tri-fuel gives you more options if fuel becomes scarce.
If you have access to a farm tractor with a power take off, consider getting a stand alone generator that will connect to your PTO. These generators are not as portable as you might like, but you have the advantage of not having to buy and maintain a separate engine.
Lastly, we have diesel. Diesel generators are in a class by themselves. Diesel generators small enough for personal off grid use do exist, but they are rare. The other issue is the cost. A diesel generator will cost many times more than a comparable gas unit and they cannot be adapted for tri-fuel.
Resources.
Yanmar Diesel makes a highly respected small portable diesel-powered generator (brace yourself for sticker shock!).
This Off Grid Ham article from 2016 discusses inverter generators in greater detail.
What is your generator experience? Tell us your story in the comment section below.
I run an Eu7000is. It is tied to the inverter with an auto start when the batteries get to the programmed low point it starts on its own, charges the batteries to full, or what I determine is full and it cools down and shuts off. All I do is fuel it every few days and change the oil at the intervals. This is winter time mode, when the sun is short and solar is lacking. Nine months of the year it does nothing.
Its almost too easy to forget about it. But $6+ / gallon non ethanol fuel helps remind me. Off grid doesn’t have to be hard.
Hey JR it’s great to hear from you again. It sounds like you have s solid setup, and as you explain it’s not necessary to run a generator all the time. That EU7000i is a genuine engineering masterpiece; I’m kind of jealous! For what it’s worth, you probably don’t need the non-ethanol gas. Your generator should run fine on 10% ethanol blend. At six bucks a gallon I admire your dedication. Around my area non-ethanol gas is sold only in hardware stores and runs about $18.00/gallon or at airports since aviation gas does not contain ethanol.
I only run ethanol mix fuel in our road vehicles. Being used regularly and the vehicle movement helps, I believe. But for small engines I haven’t had a water-in-fuel problem since going eth free. Filling the jugs is a hit but to me its worth it.
But not at $18/gal. Wow. That’s terrible.
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Thanks, Chris, you just reminded me that I need to go through mine and check them over and test run them and change the oil.
Love/hate relationship is a good way to put it. I have two, a big 8KW Generac and my little Yamaha 2KW inverter, probably the same model you mentioned. The Generac is just nasty. It suffers from all of the drawbacks you mentioned, and has a few more, including refusing to start sometimes for no apparent reason. When I test run it, it starts just fine. It only refuses to start when I actually need it. And in cold weather it’s almost impossible to start at all because the engine gets so stiff it’s difficult to turn over, even with synthetic oil and using the electric starter. Frankly I wish I hadn’t bought the thing and that I’d used the money to buy a second Yamaha inverter.
I really like the little Yamaha. It’s so quiet I hardly know it’s running, starts easy and has been completely dependable. And I can get it serviced at the motorcycle dealer that services my motorcycles. It’s kept my basement from flooding a couple of times now by keeping the sump pumps going, so it’s more than paid for itself already.
Recently I’ve been looking at the so-called “solar generators”. I say so-called because A) they aren’t solar, and B) they aren’t generators. Basically they’re just a scaled up version of the battery backup systems I have on my computers, router, cable modem, and radio equipment. There is absolutely nothing wrong with those things, but holy cow they’re expensive, and so much of the advertising for them is flat out lies. I’ve seen units on Amazon being shown running full size table saws at construction sites that in reality couldn’t run the average coffee maker without overloading it.
Hi Randall, I have a 7000 watt Champion generator, and the little Honda I mentioned in my article, which is only 1400 watts. As great as the Honda is, because it is so small it’s of limited usefulness. I mostly use it to run a battery/start booster to jump cars in the winter. It’s small enough that one person can pick it up. The Champion is another matter. I’ve had it about 12 years and my plans for it never really came to fruition, plus it’s a real beast to move around. I mostly use it to push a welder. I’m thinking of selling it and recycling that money into a Honda EU2000i. I’ll keep the baby Honda 1400 on my truck for jumping cars. I just love the Honda EU-series and I think the 2000 watter would better fit my needs and get more use.
As for “solar generators”, well, you’re right. They’re neither solar nor generators. They are really just a battery in a box, with a few cool lights and plugs thrown in. I don’t know who invented that hokey marketing term, but they should get an Academy Award for Best Huckster. As a longtime reader of this blog you already know I have derided solar generators several times in past articles. However, lately I’ve softened on them, albeit just a little. As the technology improves and more manufacturers enter the market, the prices have come down. I will concede that for certain people in certain situations, a solar generator is a practical & cost effective power solution. I may revisit this issue in a future Off Grid Ham article.
I think that looking at the solar generators again would be an interesting thing to do. I am very interested in these things for a variety of reasons, mostly because its something my wife could use easily if I wasn’t home to get the generators started. But damn you have to read the fine print carefully because these things are so hyped and actual data about capacities, amperage, etc. is buried or even not included at all in some of the ads I’ve been seeing. I’m going to have to get out the calculator and run some numbers and see what it would take to keep all of the essentials running in the house and then see if there’s anything affordable out there that could handle the load.
That’s too bad about the little Yamaha being discontinued. Damn that’s a nice little unit. It’s light enough that it’s easy to move around, is so quiet when not under load I can hardly hear it running, and it’s very fuel efficient. At least Honda makes one that size that’s just as good, maybe better. The 2KW size is just about perfect for me. Enough power to run the sump pumps but still small, fairly light and easy to use.
Chris, this is a great, well balanced article. Kudos to you.
You did fail to mention the optional parallel kits available that allow two inverter generators to sync up their output to provide more power. You can’t parallel conventional generators as there is no way to synchronize the AC phases. Those generators would fight each other.
I’m slightly jealous of Randall. Apparently, Yamaha has discontinued the 2 kW inverter model, you now have to go bigger and heavier or go smaller. I recently tried to get one of those possibly remaining in an online retailers’ stock, but no luck. Though the Hondas are more popular, the Yamahas advertise a cast-iron sleeve cylinder lining for long life at a slightly higher price. I’m going to try a no-name clone of the 2 kW inverter built around a Yamaha engine. Wish me luck.
I was responsible for contracting maintenance on a few dozen stationary standby generators at communications sites. Most generators backed up grid power, but two tower sites were off grid. The typical radio tower had an 8.5 kW 3600 RPM Onan ‘screamer” run on propane. The contractors serviced them twice per year. We figured the 3600 RPM models to last about 1000 hours of use, unless hit by lightning. That was about 15 to 25 years of standby use.
For long-term mechanical reliability, I would like to have an 1800 RPM diesel. But diesel does go bad in standby service, just not as fast as gasoline does. If you get a diesel generator, and live in the frozen north, definitely buy all your fuel in the winter. You don’t want to try getting “summer mix” diesel flowing from the tank when the temperature is below zero.
I am going to invest in a propane vapor dual-fuel kit when I get my inverter portable later this month. Propane does not go bad in storage, as long as you don’t lose it to leaks. But the vapor has to boil off the liquid in the tank, and the vapor pressure drops as the temperature approaches minus 44 degrees F or C.
Generators with more horsepower need more surface area on top of the liquid in the tanks to allow enough vapor to boil and flow in the cold. Horizontal tanks have more surface area than vertical cylinders, but multiple vertical cylinders can be joined by manifold piping to work together. I calculated that five 100 pound cylinders connected in parallel ran a 12 kW generator (derated to about 6 to 9 kW for altitude) about 200 hours in off grid intermittent battery charging mode. I expect a 2 kW portable generator should get sufficient flow from a 20 pound barbecue tank. We will see. As always, “Your mileage may vary.”
Hi Tom, you are absolutely right. Inverter generators can be paralleled together to increase capacity. I totally forgot about that.
I was not aware that Yamaha discontinued their excellent 2 KW inverter generator. I did a quick search and could not find any official confirmation that it was dropped, but I could not find any for sale either. That’s unfortunate, because in my opinion Yamaha is equal to Honda.
In my day job I am a communications electronics tech. Part of my responsibility is maintaining several backup generators ranging in capacity from 175 kw to 1.2 megawatts. All of them are 1800 RPM diesels, with fuel tanks in the 1000-2500 gallon range. The provides for approximately 72 continuous hours of power at each site before a refuel is needed. We always buy winter blend, even for summer refuels. The engines are run so infrequently that we can go 2 years without needing a fill-up, so the fuel will have to work through several season changes.