Any live-aboard cruiser who is considering a lifestyle that will require more than about 3 kW hours (regardless of voltage) of electricity daily should at least consider a generator.
I emphasize “about” because numbers like this vary based on usage profile. For example, the number where a generator makes sense is:
- Less for people like Phyllis and me who abhor the clutter, windage and vulnerability to storm damage of more than a couple of securely mounted reasonably sized solar panels.
- More for those willing to take the windage and associated sailing performance hit of large solar arrays and even wind generators.
The other benefit that many cruisers are not aware of, including me until Eric Klem sorted me out, is that when done right generators are over 20% more fuel efficient than an alternator running off the main engine while underway, and even more at anchor, as well as more efficient than Integrel when not underway—yes, even when we take into account the losses in the chargers to convert from AC to DC.
The other surprise is that a really good generator installation can save fuel and be greener when compared to renewables. I know, hard to believe, but see Further Reading for why.
So let’s dig into how to efficiently generate a bunch of power using a generator, based on my nearly 30 years of doing just1 that on our McCurdy and Rhodes 56.
Why The Big Deal?
At this point, many of you are probably wondering why I’m making such a production out of this. Surely we just install a generator and have near unlimited power, end of story?
Yes, that works, but the problem is that generators burn the least fuel per kW hour (highest efficiency) when running at about 75% load, but that’s not how most users run them.
Instead, many electricity consuming loads are installed on the boat—electric cooking, fridges, freezers, icemakers, air conditioning, etc.—and the generator is sized to supply everything all at once and charge the batteries at the same time.
But most of the time only a few of those loads are actually on, so these generators are often run for hours or even days under tiny loads, resulting in 20 to 40% more fuel burn per kW hour of electricity produced2.
That’s horrible for the planet and our wallets. And, further, running a diesel engine lightly loaded is seriously bad for it, more wallet damage.
The Best Solution
Obviously the least expensive and greenest solution is to simply cut our consumption to the point where a seamanlike renewables array can do the job, supplemented with charging from the main engine when underway anyway, and perhaps an occasional charge from the main engine when anchored.
A Good Solution
However, many cruisers these days want at least one of, and often several of, the following:
- Electric cooking
- Washing machine and dryer
- Big freezer—Phyllis’ and my environmentally bad habit
- Watermaker
- Air conditioning
- A huge array of cool electronics including Starlink
- Big autopilot
- etc.
So for us that conservation solution is not going to work.
What We Need
So what do we need to use a generator efficiently?
Could you give us a little more detail, John, on your reliability concerns with the DC generators like the Fischer Pandas? Is it with the diesel engine? Or the DC generating component? Or the electronic control system? Something else?
If the little 2-cylinder models are routinely run for more than a couple of hours at near maximum load instead of staying under the recommended 80% maximum load for long runs, then I think that I’d be concerned too how long they will last running at full load at or nearly at 3600 rpm. However, the larger 3 and 4-cylinder units, while still being lighter than a Northern Lights that produces fewer kW, run at least 600 rpm slower, so maybe if those Kubotas are generally kept under the 80% load recommendation they can be expected to last longer?
I can also seeing longevity suffering if installation and maintenance details are not attended to, but are these DC generators any more vulnerable to bad fuel, oil, air or inadequate cooling than are fixed rpm AC gensets?
Some things are really attractive about standalone DC generators or main engine systems like Integrel or the similar hybrid offerings from Beta Marine, so I wish I had a better handle on where the reliability concerns are coming from
Hi Mark,
The small diesel generators are just not as ruggedly built as a commercial level unit like the Northern Lights. They are also far more complicated with many more sensors and finally we have many anecdotal reports of problems with both DC Generators and lightly built variable speed AC units.
This would be much the same as the difference in reliability and longevity between a commercial grade engine like a John Deer and lightly built engine like a say a recreational Yanmar. (Yanmar build commercial engines too, or at least used to.) The Deer typically goes 20,000 hours before rebuild and the latter is generally done after less than 5000 and usually not rebuildable.
So I’m not saying a DC generator is a bad solution, just that a Northern Lights is a better one for those who have the room and can tolerate the weight and one I can pretty much guarantee based on my own three decades of experience and that of a friend of mine who fitted them on his fishing fleet where they ran 24/7. Also a lot of the above is based on the experience of my friends at Billings Diesel and Marine.
And sure, if we don’t install them right or abuse them, either will cause problems, that’s a given, although the NL probably less because it’s more ruggedly built.
As to Integrel, we have complete review on that, which I have recently updated, that deals with reliability and compares to a generator. https://www.morganscloud.com/2019/02/13/nigel-calders-generator-replacement-machine-part-1-what-you-need-to-know/
Hi Mark,
I am a firm believer that, for boats the size of Alchemy, 40 feet, that a DC genset (GS) is the way to go.
I turned Alchemy into a DC boat (the occasional need for AC covered by an inverter). And for 15+ years I nursed an Ample Power Genie DC GS until I had stripped off all the stuff that made it complicated and it was essentially a small Kubota engine attached to a big alternator. But it was way too often a headache, often in remote areas.
During our wanderings I ran into a handful of boats using the FP DC genset (GS). All had had numerous reliability problems. Two had turned their unit into mooring weights (as they described it). More than one had spent thousands and lost much cruising time waiting for help. I believe one cruiser was making his work for him, but I have not heard from him in years about his experience. A mechanic for an RNLI station in England where the rescue boat had an FP GS said the majority of his time was spent keeping the FP going.
As to the reason the FPs have reliability problems: one said it was way too complicated and compact and said it would be like taking a BMW engine (where you lift the hood and there is engine in every nook and cranny) and taking it into a salt water environment.
It does not seem rocket science to have a small engine attached to a big alternator with a good regulator. And they exist, but the few I know of are all bespoke: creative mechanically knowledgeable cruisers making it happen. Beyond that, there is limited demand: AC GSs are used all over: not just in boats. Very limited market for DC GSs.
There are a couple of DC GSs to be found: one from FL sounded good but getting any information from the owner was impossible. He would not say how many had been built nor would he put me in touch with any owners who had history with the unit. Everything was proprietorial. One other had limitations and none had a track record that I could determine.
I believe a generator on my size boat finds justification by the skipper wishing to have AC at anchor or by having a large freezer. I have no AC but I do have a large freezer which allows us long periods away from provisioning while still eating as usual (we do not wish to ”camp” out.)
Failing finding a DC GS, and not wishing to shoe-horn in a big Northern Lights (casual research indicated that insertion might be possible, but maintenance and or repair would be very challenging), I have gone with a Next Gen AC GS, a small Kubota engine (3kw) attached to a back-end putting out AC. This fits very nicely (no sound shield) and has worked well through 3 seasons. I am working on a write up of the unit.
Come back with questions.
My best, Dick Stevenson, s/v Alchemy
Hi Dick,
Thanks for adding your experience with DC generators.
And good to hear the Next-Gen is working well for you. Sounds like a nice middle ground between the FP and NL and a good alternative for smaller boats.
Hi John and all,
You pegged an ongoing concern of mine with AC gensets (GS): loading them up sufficiently if the boat is a DC boat and the genset is primarily used for charging the batteries.
On my AC genset I run 2 battery chargers: Mastervolt 75A and 100A. The output starts at 140+ but drops down to 90A or so in 10-15 minutes. At 80-90A a 3kw GS is not exactly loafing, but nor am I getting the amps into the battery as fast as I would like or using a better percentage of the 3kw capacity.
I can and do turn on the water heater to load up the GS, but I would far rather load up the GS by getting more amps into the battery bank faster and running the GS less time.
Much appreciate any thoughts.
My best, Dick Stevenson, s/v Alchemy
Hi Dick,
Yes, I have seen that behaviour before where the chargers drop below rating quite quickly. This might be because they don’t have separate sense wires and there is a voltage drop between the chargers and the batteries. This can result in the chargers thinking that the batteries are more charged than they are. Worth checking the voltage at the chargers and that at the batteries. Might also indicate that the batteries are sulphated. They should take full charge up until about 70% fully charges, if not that’s a pretty sure sign of sulphate on the plates.
The other option is that the charger software assumes a fixed time acceptance ~14.4 and therefore drops off shortly after the bulk phase ends (voltage reaches 14.4).
More here:https://www.morganscloud.com/2010/09/04/agm-battery-chargers/
When I ran a yard in the late 90s and early 00s I was an enthusiastic believer in an all DC boat, with a DC gen. I set several up, including Dick Stevens’, with both the Ample (I was an acolyte of Ample’s founder, Dave Smead, starting in the early 90s after attending one of his seminars, and reading his books about living on DC power, at the time their alternator regulator was way ahead of its time) and FP DC gens, as well as one called a Polar Power. In theory, this should work, however, in practice, it was mostly a failure for the reasons John states, among other things low production numbers = low reliability. While today’s DC world has advanced immeasurably, with high output alternators and big inverters, becoming the norm, and LFP batteries becoming almost standard on new cruising vessels, power and sail, a mass produced AC genset like a Northern Lights is still the most reliable way of producing electricity aboard, and the fact that it is independent of the propulsion engine is, in my opinion, a redundancy advantage.
Hi Steve,
Thanks for coming up with a clear and concise analysis. Your process of disillusionment with DC generation is much the same as mine, although yours is almost certainly based on more experience. I too was a huge fan of Ample Power back in the day. I even thought about taking out the NL in favour of the Ample. Very happy I never did that!
For others: few people, if any, have even close to as much experience with different types of electrical generation as Steve does.
Thanks, Steve. I’m curious about your experience with Polar Power. They’re still around, and have caught my attention for awhile because, on paper, their product looks interesting — but I’ve never heard from anyone with actual experience. Part of what makes them interesting is that they are the only DC genset manufacturer that I know of whose documentation states that their generators can be derated and run significantly below the ~3000 rpm mark, and they recommend doing so when trading increased weight for better longevity makes sense. Doing that means that there is no weight advantage in going with one of their DC generators instead of a fixed rpm AC genset, but I’m curious whether the longevity promise of a Volvo Penta running around 1600-1900 rpm would be enough to persuade you to take another chance with Polar Power, or whether your prior experience and ongoing concerns like limited production and distribution would still make you shy away.
Another well written article with concise and straight forward advice.
Hope this is not too off topic but it might be of value for those cruising in smaller boats. My wife and I are not liveaboards on our 32’ trimaran but we do live aboard when we take off on our 2-3 week cruises. We carry a Honda 2200CI gas generator and we only use it for heat and A/C as needed. We will never plug the boat’s shore power system in to this generator. We have a Frigidaire window AC unit that we mount into a companionway hatch adapter we built that when set in place is powered by either shore power at the marina or the Honda generator at anchor. We have a small Caframo True North heater that also plugs into the generator or shore power when we need heat. The generator is always set up on one of the boat’s amas which is effectively 13.5 feet distance from the cabin companionway and completely open so no CO risk (the generator also has a CO monitor for insurance). We will get 8-10 hours of run time on less than a gallon of fuel when operating either the heater or the A/C unit continuously. Our boat has a built in 12V refrigerator and an Engel 12v freezer that lives in the aft cabin of the boat. So far, our solar panels and Yanmar diesel engine have covered our battery charging needs well. The generator and the five gallon fuel tank we carry for it and the A/C unit both have storage bags and are placed in the boat’s ama’s when we are underway. The distancing of the generator from the main cabin due to our boat being a trimaran is a distinct advantage. This Honda generator is incredibly quiet (about 59 dB) and when running, you will really not hear it until you are about 20-30 yards from the boat (downwind).
When I retire in a few years, we hope to upgrade to a larger tri or cat and we may be looking at adding an onboard installed genset. This article will certainly be highly valuable at that time. Thanks John!
Two upgrades we made to our electrical system had the added benefit of making our (very old Onan 8kw) AC generator more useful: a lithium house house bank, and a second battery charger that could handle 120-240 AC as the input. The primary motivation for the second battery charger was to have a shore power solution in Europe, but when away from the dock (most of the time) we use it as additional load on the generator.
The generator never felt like a good way to charge our lead acid batteries, because their acceptance quickly dropped and we didn’t like to let them stay discharged for very long. I kept it in service but joked that I was just waiting for it to fail so that I could remove it and put the space in the engine room to better use. Now with lithium, I’m more attached to it. We don’t worry about the lithium being in a partially discharged state so we can schedule our generator runs for when it is most pleasant and convenient.
As the generator is still a bit big for our needs, I try to run it when we have some other electric loads we can put on it too; often when we want some hot water water for showers or if we plan to run the microwave or our small portable induction cooktop for awhile. (Incidentally, all these things run happily off the inverter too, so we never have to start the generator *just* for hot water, for example).