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Nigel Calder’s Integrel, Part 2—Is It Really Better Than a Generator?

In Part 1 of our review of Nigel Calder’s Integrel machine, we dug into how it works, why it’s innovative, my worries about reliability, and why it is neither fault tolerant nor easily repairable in the field.

And, finally, we concluded that it was too expensive and complicated to be of use to cruisers who have reasonably modest daily power needs.

But what about those of us who want all the comforts of home and therefore use a lot of power in the run of a day, or even those with one foot in each camp?

Up until now, the only realistic way to achieve that was by fitting a separate generator. Yes, I know some cruisers are harvesting huge amounts of power using renewables, but, although I think that can be done on motorboats with plenty of deck space and little shading, doing this on sailboats results in un-seamanlike clutter and windage. Yea, I know, that’s not a popular view, but when did that ever stop me?

So before you go any further into this chapter, you may want to take our simple test to see if you even need a generator, or Nigel’s Integrel machine.

Also, those of us who have an even tiny bit of lust for all the comforts of home, as promoted by Triskel Marine, Nigel and Paul Shard, should read on, since we will cover what that’s really going to cost us, in complication, aggravation, and money, with Integrel or a stand alone generator.

OK, still with us…you luster after all the comforts of home, you?  Let’s shine the bright light of arithmetic rigour and analytical thinking on this thing.

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More Articles From Integrel Review:

  1. Nigel Calder’s Integrel, Part 1—What You Need To Know
  2. Nigel Calder’s Integrel, Part 2—Is It Really Better Than a Generator?
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Dick Stevenson

Hi John,
Excellent article and analysis of power generating even aside from the focus on Nigel’s contribution. With your other articles, the whole is a great and realistic model for any cruiser, experienced or otherwise, to think about their power needs and approach designing a system to meet those needs.
You report MC being in the 200-400 amp range and that you do an hour or so of generator running per day. I am curious about the battery charger set up you use: is it one big charger or a few strung together? What is the initial amp output if you start at 50% depleted and how many amps are being put into the battery bank when you reach 80% about an hour later?
I am also curious about whether there is a drop-off in amp output when you add load such as a water heater.
My little experience with AC gensets is that it is hard to get the full kw capacity of the genset into DC amps, at least in any sustained way. Then, when you tried to load up the genset by adding loads like the water heater, the output of the battery chargers drops.
Thanks for your thoughts,
My best, Dick Stevenson, s/v Alchemy

Jean Jutras

There is another alternative to recharge batteries. Each summer, I am cruising New England for 3 months and when I anchor in an idyllic harbor I do not appreciate to have my pleasure ruined by other boats starting their generators. If you are cruising in popular places, you know what I mean. This can become horrible. I have a DC Fischer Panda and I stoped using it in 2015 when I had an EFOY 210 installed in my Cabo Rico 42. I loved it immediately. I would not cruise without it. At anchor, we can enjoy music or silence on board and this is priceless. The EFOY has zero maintenance, do not beak, can be used sailing or at anchor and operate in an auto mode. I start my season bringing 10 gallons ($900) on board. I can be anchored for days up to a week and never have to start my generator. I run a freezer, fridge and electronics and need about 250 amps per day. My solar panels with the fuel cell do provide all the amps I need daily. For me, the Efoy is the second most valued item on my boat, after the autopilot.

Jean Jutras
s/v Mahi Mahi


Excellent article…little bit wordy but Nigel Calder pieces are not brief either ?
All this hoopla only strengthen my belief that “conservation is better than generation”. If somebody wants all the comforts of home buy a home. BTW in many tripical countries beachfront property will cost less than the whole Intergel system and the breeze is free….keep up the good work John!


Some Nordhavns take a more efficient approach to power generation underway, obviously does not change the consumption. They typically have hydraulic stabilising fins driven by a pump on the main engine gearbox PTO and this system can be expanded to include a hydraulically driven A.C. cruising generator

Conor Smith

Steve Dashew experimented with that, I believe, in some of his early sundeer boats. He had a hydraulic PTO running a crash pump, generator head, and something else I thought too. The blogpost said in the end it did not work the way he hoped.

Dick Stevenson

Hi all,
I am rather surprised and curious about why Nigel, or one of his team, has not responded to John’s article and the comments generated. Just as I appreciate it when principles get involved (like the man who commented on Colin’s anchor article), I notice when an article gets ignored. The marine community benefits from a respectful give and take.
My best, Dick Stevenson, s/v Alchemy

evan effa

I bought a used Nordic Tug 37 with an oversized generator (Onan 9 KW diesel).

I am quite motivated to keep my generator use to a minimum for aesthetic and environmental reasons and out of respect for any neighbours we may have. The generator is very quiet but I like to keep the runs to minimum. I have 550W of solar on the roof and in sunny conditions have most of daytime needs and more covered. In the wintertime though at anchor, with less light and using the diesel heater 24/7, Fridge and freezer etc. the daily draws are around 350 Ah.

Anyways, after studying this problem at length and considering LiPO4 we opted to go to batteries that will accept a charge more quickly and tolerate partial state of charge without damage.

We opted for a 6 x 110 Ah (660 Ah) Firefly Carbon Foam house bank. The advantage to these is they will take up 250A of charging each… (6 x 250 A = 1500A -> way more than I can generate.) They can be quite happy being drawn down to 20% SOC and will be undamaged if I only charge them to 80 % capacity. Using a 125 Amp Magnum Charger along with a Xantrex 40 Amp charger +/- the engine with its nominal 160 A alternator we can get up to 200+ A of charging when making a short hop or a max of 160 A when on the hook. It still works out to 2.5 – 3 hrs a day of generator time in gloomy winter weather. (In the summer, with lower consumption and much more solar power, we can go many days without a generator run unless we need hot water for showers etc.)

I think redundancy is important. Having multiple ways to charge the house bank (Solar, Shore, Generator, Engine) makes more sense to me and won’t break the bank.

I do not think that I would opt for a system that relied solely on the engine for charging.


evan effa

Addendum: Having to run a generator an extra 2 hours in a very low state of draw, just to top off the AGM SOC to 100%, simply for the health of the batteries is a real nuisance. Typical AGM’s demand that you do that though. A good reason to consider Lithium or Carbon From instead.


evan effa

Thanks for pointing out that salient point around reduced overall life span with frequent Deep (80% draw) cycles. I was under the impression that the Carbon Foam Batteries could be drawn down to 20% SOC with impunity but I suppose their ability to come back to full capacity after deep discharge is not without a down side; reduced overall lifespan.

I suspect that these deeper cycles to 20% SOC would take the system into voltages below 12.0V; another reason to avoid drawing them down so much. (Many of our electronics and for sure the Wallas Heater does not like voltages below 12.0V)

So far, we are able to make our system work without more than 50% draws and the ability to shut off the generator before achieving 100% SOC is a real advantage.


Martin Hassellöv

Hi Evan,
According to Firefly specs the life expectancy relates to depth of discharge as:
DOD Cycles
30% 9000-13500
50% 3600-4200
65% 1800-2400
80% 1000-1300
100% 600-800

I am just reading here, but it seems from the specs it really pays off, also for these, to drain as little as possible between recharge.


The main hurdle for me with the “machine” is the lack of redundency. Having a generator onboard gives you redundancy for power generation in case something happens with the engine on an offshore passage.


Perhaps I just don’t grasp the problem or maybe I can’t grasp why this problem is still a problem. It seems the issue is that if a diesel engine isn’t properly loaded, the engine suffers a shortened life without occassionally increasing the rpms to blow out cylinder glazing.

I hear car companies pitching eco-drive engines that shut doen cylinders when their output isn’t needed (ie, highway driving). So why hasn’t somone applied the same theory to diesel engines?? What am I missing?

Great topic! Much thanks!


As usual, John, an excellently written article. It might be wordy, but there is no section I would have desired not to be there. In order to do a real-life comparison of Nigel’s new offering, I believe it was absolutely necessary to bring in, and contrast, all these other options, and explain them in terms of how they apply in real life. Well done!

Though I don’t see it on the immediate horizon, I still envision a day when we can have cruising boats that are entirely electric, in terms of propulsion, cooking, and heating/cooling. I think the required storage capacities for long-lasting, safe, and completely maintenance-free batteries are just around the corner. Energy harvesting from renewable sources is improving in leaps and bounds, and are, with a bit more real estate, available to many of us right now. The fill-in/catch-up/emergency energy generator, not running on diesel, and being completely quiet, safe, and dependable, is probably the one that’s furthest away. The lack of this component, however, can be overcome by a better implementation of the former two.

Prem Lee Barbosa

that’s one large corner!

Martin Hassellöv

Hi John,
Thanks for insightful (and amusing reading). When I watched Nigels video first thought, yea, clever, why hadn’t anyone thought about that, but on the other hand it all come back that typically putting on a huge alternator on the engine (regardless on how you regulate it) is not the answer to the fundamental problem with lead acid batteries of most sorts. The internal resistance of the lead acid batteries just don’t take all that charge. You laid it out in much more detail, but yes I think you are spot on that not only due to the 50-80% SOC window issue, but also the amount of current the batteries can accept (yes Ohms law again), will only make it really sensible for Li and possibly Carbon foam chemistry.
I have a 170A, 24V Prestolite heavy duty alternator which can be found for a very modest price, retrofitted with a three stage regulator. It provides as much current that the batteries accept typically when on the move. Other use profile I recognize the same installation and management philosophy as you describe: nice quite operation of the genset when needed and then run also the AC freezer, and calorifier, or water maker to make the most use of the available power. Renewables are used to extend the time to charge.

Research and innovation is not bad though, we should encourage small vessel research of all sorts I think, which is such a tiny sector. Nigel did a very nice contribution to an EU project some years ago on diesel electric hybrids and Bruntons autoprop did some development there too. I think as was said, 10-20 years down the road, we will probably not be burning fossil diesel to power our sail boats, who knows what kind of technologies will come in being it fuel cells or batteries based on graphene or something else, but it all comes down to energy harvest storage and use, we cannot trick that. I am sure we will see use of the Integral approach in various diesel electric hybrid solutions in the next few years. But I think it is best tested in small work boats, that can run electric in and out of the harbors or service boats to aquaculture facilities etc, where early adopters to new technology can be close to assistance and service if unexpected failure occur. Off shore yachts are probably abit slower to take on novel technologies for natural reasons. My main resistance would be to the “black box” that is too difficult to trouble shoot or applying intuitive experience gained on conventional systems, although the tech talk by Nigel was really impressive and fascinating.

Conor Smith

Great article as always.
I think one of the best uses for this system would be pilot boats, water taxis, and ferries, which run air cons. For water taxis, let’s just say they run 20 minutes and then wait at a dock for 10 minutes before getting underway again. Or pilot boats (kind of like nordhaven example I guess) they have a AC generator running the whole time the main engine is running (at least here in Miami). These are perfect examples to completely replace a AC generator and make huge efficiency increases.

Paulo Reisdorfer

Hi John,

Have you by any chance followed up on the Integrel system? They’ve recently claimed it has been tested and approved by Volvo Penta France for their D-range engines.

Also I’m wondering if anyone here on AAC has had any first hand experience on the system?

Philip Wilkie


Like MalL I’m local to the Safiery solution and I’ve talked to them as well. The Lithium Titanate battery I’ve built is a 24v bank with an internal resistance of barely 2 milliohm, so decent alternator regulation is essential.

This combined with all my other electrical gear being Victron makes their Wakespeed solution pretty compelling for me.

I also talked to the local alternator supplier, Rapid Power, and they confirmed the 85% efficiency claim is at the top end of what’s achievable, but way better than the usual 50%. But in this case I’m cheaping out and going with a standard brushless alternator they have on the shelf for far fewer dollars.

From where I’m sitting the Wakespeed regulator box (less than A$800) ticks all the boxes you have spoken to previously. I might even be able to afford a spare 🙂

Philip Wilkie

The 85% claim is on the Safiery site here:

“With an efficiency approaching 85%, upgrade to this High Performance Alternator with a 250A rating. ”

It’s a bit vague I accept. If I was to put good money on one on this basis I’d need to see some real data. Rapid Power’s own website doesn’t mention this claim, but then in conversation with them on other matters, they admit it’s way out of date.

They aren’t cheap, but I independently know they have a strong market in Queensland Fire Service and mining industry, both of which demand rigorous specifications on their mobile plant equipment.

It’s a specialised small shop, when you ring you are likely to talk to the owner.

Robert McArthur

Our engines – Perkins M135 – have a limit of 6kW on the PTO which I assume means to anything off that end of the engine, alternator included. Would that be right?
As we would be seeking to maximise output, the efficiency of the alternator is paramount as the difference between 58% and 85% is 3.5kW vs 5.1kW at the max 6kW/8hp of the engine. The 5kW alternator would be 2.9kW vs 4.3kW at same percents. Given the large difference is probably just heat produced, it is definitely worth paying more for a higher efficiency alternator!

Robert McArthur

Hey Mal, I couldn’t reply below but I am very interested on the Safiery possibilities. I’ll talk with Bruce too. I agree with John to about its relation to Integral – Nigel’s advantage is the strong connection with the motor and it’s performance, getting the most out of it depending on how it is being used, combined with charging benefits for particular battery packs. The Safiery is just a good alternator, but the charging benefits seems to be maybe more broadly applicable do different battery packs.

Robert McArthur

That Balmar is interesting but not sure of the efficiency compared to the Safiery (or others) – Balmar say it can do 100A at 48V, or 4.8kW. Yet the table shows that alternator takes up to 11hp off the PTO. So at Full 4.8kW it’s only 58% efficient?!

Robert McArthur

Looking forward to your thoughts and writing on the new regulators!

Also, what 48V gear is out there that you feel needs to be there before 48V can become more widely used? I have heard of windlass and bow thrusters. Perhaps autopilot too?

Per Kjellqvist

Great article, I signed up for this one and am now hooked to your site.

My first impression when I watched Nigel’s video presentation was – wow, but then I started thinking about it and came to many of your conclusions. In general my main aim is to keep things on a liveaboard yacht as simple as possible and with redundancy. The Integrel system fails all of that.

Then I started to wonder why they didn’t design a separate Integrel generator of sorts. What I mean is a separate small diesel engine (Kuboto or something reliable like that) which only runs an Integrel alternator. Since the Integrel computer regulates the rpm/load balance that engine would not have to run on high load all the time as with a normal generator. You would then have redundancy i.e. not only relying on the main engine.
Having said that it still doesn’t remove the cost and complexity of lithium-ion batteries.

I am sticking with my 9Kw Onan generator and 960Ah liquid filled lead acid battery bank (2 sub-banks connected in parallel, each using 6 x 2V batteries) for now, but keeping an open eye on new development in battery and generation technology which is a field that is moving very rapidly now.

Peter P

Hi John, I just signed up tonight on the strength of your well written thoughts on the Integrel System. I have a FP Elba 45 on order delivery around May 2021 La Rochelle, I am in Melbourne Australia. I ordered the Elba 45 with few options ticked apart from electic winches, washing machine, so I can start with a clean sheet of paper and fit it with the most efficient reliable systems and in the process remove the need for a gen set, gas and petrol from the boat.
The Admiral, her must have’s include induction cooking and everything other electronic device known to mankind, and I driven by wanting to rid myself of a third diesel engine, gas, and petrol, (lithium outboard engine) the Integral on paper seem to offer all of these combined with solar, so I am waiting on a quote for the Integrel system with 28K of Lithium and 1500 of Solar, with a 5K Victron Inverter but as you have pointed out (apart from the cost) maybe I need to stick to my original plan ‘A’ which is a Fischer Panda Neo 5K with 1500 of solar ( solar is cheap) running one 16000 BTU Dometic in the saloon with a second 8000 BTU and two 8000 BTU in the owners hull, FP have advised that the Neo would handle the aircon as long as I did not try and start all three Dometic air con at once the issue with the Dometic is the start up draw.
I am now researching the Italian made Frigomar which is variable speed and would suit the Integral system due to a low start draw, whereas the Integral I doubt would run the Dometic.
Whist another brand of whatever may have advantages service and backup considerations may overide that advantage.

Service and backup of brands under consideration, Integral unknown, Frigomar unknown, Fischer Panda somewhat unknown, Dometic air con no problems, Onan gen set, no problems reliable had 8 years on a 7 KVA Onan on my previous Lagoon400 plenty of back up and spares, however heavy and big.
My original plan ‘A’ the Fischer Panda 5000K Neo (weight 75KG), with 15000 of solar, Lithium 5K Victron inverter. The weak link in plan ‘A’ is the Fischer Panda Neo, one dealer thought of it as a toy, not to be taken seriously. I simply do not know. Welcome any comments. The Integral system has a lot going for it.

Rene Blei

Hi John,
My Northern Light 5.5 kw M673M 220V Genset, suddenly stopped producing any voltage, (Herz still shows a reading) and was told that the voltage regulator is the problem and needs replacing. So my question is what is involved? Is this a DIY job and the cost for a new one?
Many thanks,

Rene Blei

Thanks John and yes a little knowledge can be dangerous. As a kid I got a 220V jolt while leaning against a radiator, so I received my antidote 🙂
Maybe a fellow member has come accros this rare issue.
Thanks again.

Willem Henry Spek

In my experience the investment you mentioned for an Integrel of $ 50.000 is not correct. We installed an Integrel system with 14.2 kwh LFP batteries. The investment was Euro 30.000. The system works great. We did not have space for an generator, and if we did, the investment would have been the same (we compared it with a whisperpower picolo). So, in my opinion you are to negative about the Integrel as an alternative for a generator.

Prem Lee Barbosa

It’s been a little over a year. How is it going?