The Offshore Voyaging Reference Site

Replacing Diesel-Generated Electricity With Renewables, Part 2—Case Studies

In Part 1 we looked at how renewables (solar, wind, and hydrogenation) can contribute to cruising without the need to burn diesel fuel just to make electricity, either in a generator or using the main engine.

By the end of that article it became clear that for those of us who use substantial amounts of electricity (most full-time live-aboards these days) a renewables-only solution is not going to work without festooning our boats with huge unseamanlike and drag-inducing arrays of solar panels, wind turbines and hydrogeneration.

But wait, if we stop just thinking about renewables, and get practical, this is a solvable problem on many boats.

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More Articles From Online Book: Electrical Systems For Cruising Boats:

  1. Why Most New-To-Us Boat Electrical Systems Must Be Rebuilt
  2. One Simple Law That Makes Electrical Systems Easy to Understand
  3. How Batteries Charge (Multiple Charging Sources Too)
  4. 5 Safety Tips For Working on Boat DC Electrical Systems
  5. 7 Checks To Stop Our DC Electrical System From Burning Our Boat
  6. Cruising Boat Electrical System Design, Part 1—Loads and Conservation
  7. Cruising Boat Electrical System Design, Part 2—Thinking About Systems
  8. Cruising Boat Electrical System Design, Part 3—Specifying Optimal Battery Bank Size
  9. Balancing Battery Bank and Solar Array Size
  10. The Danger of Voltage Drops From High Current (Amp) Loads
  11. Should Your Boat’s DC Electrical System Be 12 or 24 Volt?—Part 1
  12. Should Your Boat’s DC Electrical System Be 12 or 24 Volt?—Part 2
  13. Battery Bank Separation and Cross-Charging Best Practices
  14. Choosing & Installing Battery Switches
  15. Cross-Bank Battery Charging—Splitters and Relays
  16. Cross-Bank Battery Charging—DC/DC Chargers
  17. 10 Tips To Install An Alternator
  18. Stupid Alternator Regulators Get Smarter…Finally
  19. WakeSpeed WS500—Best Alternator Regulator for Lead Acid¹ and Lithium Batteries
  20. Smart Chargers Are Not That Smart
  21. Replacing Diesel-Generated Electricity With Renewables, Part 1—Loads and Options
  22. Replacing Diesel-Generated Electricity With Renewables, Part 2—Case Studies
  23. Efficient Generator-Based Electrical Systems For Yachts
  24. Battery Bank Size and Generator Run Time, A Case Study
  25. A Simple Way to Decide Between Lithium or Lead-Acid Batteries for a Cruising Boat
  26. Eight Steps to Get Ready For Lithium Batteries
  27. Why Lithium Battery Load Dumps Matter
  28. 8 Tips To Prevent Lithium Battery Black Outs
  29. Building a Seamanlike Lithium Battery System
  30. Lithium Batteries Buyer’s Guide—Part 1, BMS Requirements
  31. Lithium Batteries Buyer’s Guide—Part 2, Balancing and Monitoring
  32. Lithium Batteries Buyer’s Guide—Part 3, Current (Amps) Requirements and Optimal Voltage
  33. Lithium Battery Buyer’s Guide—Part 4, Fusing
  34. 11 Steps To Better Lead Acid Battery Life
  35. How Hard Can We Charge Our Lead-Acid Batteries?
  36. How Lead Acid Batteries Get Wrecked and What To Do About It
  37. Equalizing Batteries, The Reality
  38. Renewable Power
  39. Wind Generators
  40. Solar Power
  41. Watt & Sea Hydrogenerator Buyer’s Guide—Cost Performance
  42. Battery Monitors, Part 1—Which Type Is Right For You?
  43. Battery Monitors, Part 2—Recommended Unit
  44. Battery Monitors, Part 3—Calibration and Use
  45. Battery Containment—Part 1
  46. Lithium Buyer’s Guide—Budget: High End System
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George L

In my experience, this is spot-on. We extensively evaluated many options and came to very similar conclusions
–        Solar removable so it won’t interfere with sailing
–        Efficient generation from the engine is very important, expecially considering that there is much more motoring than anyone likes, especially when travel schedules have to be met
–        Diesel is often the most practical solution and given the paltry burn rate of an efficient setup not the end of the world
–        Get enough battery capacity

Rather than having an engine and a generator, we are installing two combined units with highly efficient  permanent magnet generator heads in-line off the PTOs. Betamarine did a great job putting this together for us and provided most useful engineering advice throughout the project. Because usually only one engine runs (if at all), it is loaded much better – more efficient and better for the engine.

We are installing wind generators and together with the portable panels, we take advantage of all the free power we can get. If that’s enough great, if not, a little bit of help from engine/generator will sort it. We have a small arc anyways (integral with the boat) and otherwise a very clean boat, so we’ll see how much the damage on performance they are in the end. I guess we could take them off for longer passages, if it’s really an issue.

Our dislike for propane prevailed in the end, the final nail in the coffin was three weeks in Scotland without propane because somehow they couldn’t sort out bottles. A lot of arguments can be made for propane but having one system less on board and having good electric appliances tilted the scale for us.

Andre Langevin

I can’t agree more with the conclusions. I’m not a good fan of added generators mostly because i don’t have the space on my sailboat and i think its redundant (which might be good for northbound boats but non necessary for Carribean boats where sun shines all the time). But with a 250 Amp Balmar alternator i can provide 200 reliable Amp of charge to the 800 Ah Lithium bank every time the engine run. (picture) And to maximize the solar yield i have folded 4 panels in accordion over the 2 panels on the roof. So when at anchor, i can unfold them and get 1.5 Kw of solar when the sun shine. With water production being now covered by the abundance of Ah, ice making also, what is left is a project to install a 12 volt element on my water heater so that i don’t have to run the engine to heat water. I’m mostly completely solar when at anchor even though Starlink runs 24 hours.

Eric Klem

Hi All,

Indeed, making hot water takes a huge amount of energy and as a result is ideally done using waste heat or at a time of excess energy availability which ideally you should not have very often (maybe at anchor with a portable solar array). In many domestic cases, about 20% of house energy needs are hot water, this is the reason why you see interest in solar hot water heaters although cheap PV has now meant that most people do it electrically as you can grid buffer.

Let’s say you want to take 30L (7.9 gallons) of water from 22C (72F) to 60C (140F), the energy change is 4.8E6J or 110Ah @12V with no efficiency loss. In truth, there is efficiency loss and I would expect it to be more like 130Ah for the initial pull down and then an additional 150Ah to maintain temperature each day with no water usage. Each bit of water that gets used needs the replacement water to be heated using the same energy ratio of 4.3Ah/L so it is not hard to imagine maintaining hot water being somewhere on the order of 300Ah/day if you use a tankful and this is for a boat with a small water heater and modest usage, if you want to shower like at home it goes way up from there.

I think it is also possible to do somewhat better than these numbers. The 2 most obvious things to me are:

  • The insulation on most hot water heaters is pretty poor, they assume you don’t care about efficiency. Adding a lot of insulation could take the 150Ah/day that I budgeted for maintaining temp down to maybe 50.
  • Don’t have hot water all the time. If you only make hot water starting 2 hours before shower time (at a load of almost 700W), then you don’t have to maintain the temperature for the rest of the day. As the temperature drops, the differential will drop and it will lose energy more slowly but of course you do need to do the initial heat up again. Of course, if you have excess energy either engine waste heat or excess renewable energy, you should of course take advantage of this and use it.

I have looked at this one for ourselves and always concluded that the right thing to do in our case is to work the shower schedule around when we need to motor. Because we let the tank go to 190F (our engine thermostat setting), it is still showerable at 12-18 hours after motoring providing some flexibility.


Matt Marsh

If you are seriously thinking about using 12V or 24V electricity to make hot water, and intend to do this on a frequent basis, then a resistive heating element may not be the best way to do it. Using a DC refrigeration compressor as a heat pump to extract heat from ambient water or air, and dump that heat into the hot water tank, is 3x to 5x more efficient. The cost and installation labour of such a setup, however, is only justifiable if it’ll be used regularly.
It’s rather telling that all cold-climate road-going EVs have now abandoned electric resistive cabin heating in favour of this scheme.

Andre Langevin

Hi Matt if we could pump all the surplus heat from refrigeration to the water heater…we would be in the amperehour paradise 🙂 But alas the plumbing and pumps required to do that is too tedious to do.

there are 12 volts 600 watts element that sell with a controller that only switch them on with surplus energy (Lithium over 13.8 v). In my case under the Antilles sun after 1pm i litterally dump solar energy because the Lithium are full. I make water with the 110 V x 9 amp AC motor but that is just for an hour. I will certainly find a way not to lose that solar. I have found a device that convert 115 AC to 115AC but with a variable amp output. That could be very usefull to set it at say 4-5 amp and let a voltage switch and a relay on the BMV supply 400-500watt to the heater while there is surplus. That would defeat the reason to have 12v element and i could keep the 115AC element for when we use hot water at a marina.

Vesa Ikonen

Hi Mal.
Loads of people heat their homes with a reverse cycle aircon here in the Nordics, with long, arctic cold winters.
They are just called heat pumps instead of reverse aircon.

Typically an air-to-air system (basically a reversed aircon) gets 2-3 kWh heat for each kWh electricity used.
Air-to-water might get 3-4 times yield, and a water-to-water (pumps heat from a very deep well) might get 4,5-5,5 times yield.

Air-to-x systems do just fine in temperatures WAY below freezing point – but of course not as efficiently as in more moderate climates. Typically they work until about -15 celsius.

I could easily imagine heating water with energy from seawater in warmer climates – as I have been heating my home with near freezing water from a well in -20 celcius ambient temps for years.

Stein Varjord

Hi Vesa,
Heat pumps are made for bringing heat inside. AC systems are made for the opposite. Even though the principle is indeed the same one, and several units can even be reversed to do the job of the opposite unit, efficiency is apparently vastly different.

I haven’t measured this myself, but have done some research. According to two producers, an air to air AC in reverse will have close to a 1:1 efficiency, meaning zero benefit, and only as long as the outside air is not noticeably below freezing. Same goes for reversed heat pumps (rare). They might cool, but an actual AC unit will usually be far more efficient.

I don’t know enough about the physics of this to explain why, or if it could be done differently, but I find it interesting. I’m discussing with a maker if they could supply some key components for a water to water het pump system I want to build. Simple principles, but hard to get it all together.

Dan Perrott

John you will not like our setup. We have 400W of solar on an arch and added a wind turbine.
The solar alone kept up except when we had cloudy days and weren’t moving. I hated running the engine at anchor just to charge the batteries.
For us the wind has been a fantastic addition. It has completely negated needing to run the engine for charging. Its all about diversifying our energy sources. The wind turbine typically provides power when there is little solar available.
This means that all the diesel we carry is available for propulsion when we need it, and not required for topping up the batteries on longer passages.
It also means we can sail on and off anchor when we like without feeling well we need to run the engine to charge anyway…. Since we have the engine on we may as well motor….no point getting the main sail out. It’s an easy slope to slide down.
We are a simple boat with our biggest power draws being a fridge and autopilot.

Dan Perrott

If we motored a lot then the added windage would make a difference, however if there was enough wind to cause this windage difference we are normally sailing.
It would be interesting to be able to just take it all off and observe the difference but I think I might be happier not knowing and enjoying energy self sufficiency.
The energy self sufficiency allowed a zero engine hours crossing from the Caribbean back to the UK via the Azores.
It also removes any need to solve significant engine troubles while underway. (I know they shouldn’t happen but they do)

Jeff Totman

I think the pros/cons of a wind generator depend a lot on where you’re located. When I bought my boat it had a KISS wind generator and in the 10 years I’ve owned it has been trouble free with virtually no maintenance, fingers crossed. It’s mounted on a single 4” diameter pole so the weight and windage isn’t significant on a 50,000# cruising sailboat. BUT, here in Maine and along the east coast of the US, it doesn’t make much of a contribution for the simple reason that the wind is so inconsistent. But when/if I ever manage to take this boat sailing in the Caribbean where most days offer 10-15 knots all day/night long, the KISS contribution would be considerable and IMHO well worthwhile.

I dislike the looks and windage of a radar arch loaded with solar panels but I did want to add solar to my charging system. I also have regular appointments with my dermatologist who reminds me to avoid being in the sun too much. So I wear an hat and added a hard top over my cockpit and used 2 sided tape to mount 2-175W flexible panels that are invisible from the side and add no windage and are supposedly ok to walk on, though I avoid doing that as much as possible. The hard top is flatter than a canvas bimini so probably slightly less windage than what was there before as well as offering better visibility to the sides. It also has 2 hatches on the centerline that can open and lay flat but even when they are closed i can clearly see my mainsail through them from the helm. The 2 solar panels are oriented along the outer edges of the hard top with about a 3.5’ space on centerline between so, while some shading does happen, it doesn’t seem to be a big problem, probably partially because with a roller furling mainsail, at anchor there’s no bulky mainsail and sail cover just above.

I m also a fan of my Northern Lights 5kw genset paired with my 150Amp battery charger. I start it about 20 minutes before shower time and let it run for 90-120 minutes, burning less than a gallon of diesel while providing plenty of hot water for showers and leaving the 12 gallon hot water tank full of hot water for dish washing or additional showers. As soon as the charging rate into my 840Ah house bank falls below about 120A (usually not long because solar and wind generator contributions keep batteries from being drawn town too far), I start my Watermaker which draws about 30A, yielding 19 gph of fresh water.

Underway, my alternator maxes out at 120A, so not huge, but I find it’s adequate and not worth the extra cost to convert to a bigger one that would require a serpentine belt and accompanying pulleys. On days when I need to run the engine other than the few minutes it takes to get on/off a mooring, I find it’s usually needed for a lot more than a few hours. If there’s a fair wind and I can sail all day I just run the genset for a couple hours much like I would while at anchor.

That’s the setup that i think makes sense for me on my boat but one reason I think this is such an interesting subject is that between individual boats with different configurations and different owner priorities there are so many variables that it’s an area where there truly are many right answers.

Eric Klem

Hi John,

These are great case studies and different ways of dealing with this. Andy’s way is similar to a way that I had been thinking of in terms of having a huge battery bank so that you can sustain yourself until you get to a point with lots of charging. I had coastal cruisers in mind where most people will do significant motoring or go to shore power at least once a week so if you have a big enough battery bank and big enough alternator, this would work just fine. In an instance like this, renewables would just allow you to make the battery bank a bit smaller and also the alternator a bit smaller. It should be noted that if we want to look at this environmentally, the embodied emissions of big lithium battery banks are quite significant and need to be considered. Someone like Andy does pretty well I suspect as his boats are in constant use so his bank will have done a ton of cycles by the time it needs to be replaced but the weekend warrior who puts a huge bank in so that they never need to charge during their annual 2 week cruise will find that the numbers look pretty bad.

In our case, we have a setup where the renewables can keep up in really good weather but fall behind quickly in poor weather. The battery bank is big enough to hold us over until we do some motoring and the big alternator will quickly get us back to a place where renewables can finish the job (lead acid bank so absorption is slow). We definitely motor a lot less than most people around here and try not to start up to get on and off the anchor when possible but even with that, we do motor often enough and the big alternator lets us do some real charging. We do have a field disconnect on the alternator so that we can be propped appropriately for wide open operation and also be efficient at normal cruise speed.

One way to think about the diesel use is that for an installation with a normal 12V alternator, at cruising speed you use approximately 1.7 gallons of additional diesel per 1000 Ah @12V generated (I am using a diesel efficiency of 230g/kWh here which is pretty common for a fuel island plot and a 50% belt and alternator efficiency). If you are just charging in neutral, your efficiency will be much lower as you will be at a much worse point in the fuel island plot. It should be noted that the charge levels we are talking about to keep run times down can be quite high for boats with smaller engines. A typical 40′ cruising boat might use 12-14kW for propulsion at a normal cruise speed with an alternator putting out 150A at 14V which will add an additional load on the engine of somewhere around 4kW.


Eric Klem

Hi John,

The Ford Lightning is an interesting one, if you are coming from a Toyota Corolla, it doesn’t look so good but if you are a contractor hauling a lot of stuff who is deciding between a gas F150 and the Lightning, it looks pretty good. Looking at it from a lifecycle standpoint, the embodied emissions to build EV’s is much higher than a gas car but then the emissions from usage are way lower (this is the majority of the emissions of all cars) and the end of life emissions are still pretty speculative. There have been several studies on this but in general, we can all feel good that the emissions will be significantly better for a comparable EV over the lifecycle as it usually crosses over by something like 30k miles or less and then just gets better from there with normal power sources. Unfortunately what this shows is just how inefficient internal combustion cars are, even Atkinson cycle engines are not that great although they are definitely better. The hope is that batteries start to be recycled then the embodied emissions of the batteries made from recycled batteries will be much lower. To your point of no free lunch, while a BEV has far better lifecycle emissions (less than half typically), they are still quite significant so it doesn’t mean we can build as many as we want and drive as far as we want without consequence. The lifecycle emissions have the exact same things to watch out for in boats. The comparison that is less clear is comparing a plug-in hybrid car and a BEV, that comparison is much more dependent on use case and specific vehicles (or boats as it is not all that different).

Unfortunately it seems like consumer behavior is negating a lot of the good engineering and manufacturing improvements and I see many parallels to the boating market. Here in the US, the growth in size of vehicles, the move to most vehicles having AWD and people driving 85mph instead of 60mph which requires twice the power are really making it tricky.

I hope that another big leap forward in battery technology will make a lot of this less big of a deal although when it will happen I am not sure. When I was building the first electric car I built in the late 90’s, lead acid was what almost everyone was doing and the core technology was over 100 years old. The first “laptop battery” (lithium) car I ever saw was at the Tour De Sol in the early 2000’s and due to a combination of inadequate safety mechanisms and unsafe work practices, there was a big fire with some bad injuries. Lithium batteries have definitely improved some but the progress has been incremental, hopefully the huge amount of research going into batteries will pay off soon in terms of energy density, cost, embodied emissions, etc.

I hope this wasn’t too off topic.


Jeff Totman

I don’t disagree with your analysis of the relative green-ness of the Lightning truck as far as it goes, but I think you’ve unintentionally left out a pretty big part of the equation. Right now, while EV’s are still a small percentage of total vehicles on the road, you can plug your Lightning truck in at the end of a work day and it’s ready to go the next morning with a full charge. That works great for early adopters who are home every night and don’t travel very far each day. But what if all your neighbors were doing the same thing? That would require a huge investment to replace much of the existing power lines as well as much more electrical generation capacity, both requiring large amounts of energy to produce and put in place and operate. That will have to become part of the equation. So far, while EV’s are relatively uncommon we have been able to get away with using existing electrical infrastructure without having to think much about where that energy is coming from, but if the conversion to EV’s continues so most everyone has one, we’re going to have to address how to get power to all those home charging stations as well as the faster charging stations travelers away from home use. Also, since even these so called fast chargers take significantly longer to “fill the tank” than it takes to pump 25 gallons of diesel or gasoline, think of the lines of vehicles waiting their turn unless clusters of chargers number in the hundreds in one place all along our highways, along with the infrastructure required to support them. Also, that 25 gallons of gasoline will take my Chevy V8 pickup with technology that turns it into a V4 that gets better than 20mpg on the road will go 500+ miles without having to take an extended break, but the Lightning will need to make 2 much longer stops to go the same distance, significantly increasing total travel time. I just think that any discussion regarding the pros and cons of EVs versus traditional vehicles is misleadingly incomplete when these issues I’ve just mentioned aren’t included. When you look at the whole picture, I don’t think it’s quite so obvious that making such a huge investment in infrastructure to replace the existing infrastructure is a good idea unless we’re pretty sure that other, better options such as hydrogen powered vehicles won’t be available just about the time we get all set up to support EV’s.

Paul Y

This was Integral’s sales pitch, us the diesel fuel map “white space” to get cheap electricity. You can do the same with a very large alternator and good regulator. I have a WS but the new brand just released is much superior

Whitall Stokes

Hi John,

Don’t worry, the M&R56 will not be getting an arch! Not a fan (ouch) of wind generators either. I’ve experienced how much leeway is induced by 400watts of solar on an arch trying to get upwind as a boat heels over. Ability to stay off a lee shore is too important, especially in high latitudes where winds change direction suddenly and forcefully. I’ll admit to having a little OCD about clean decks.

Lithium and a larger alternator & WS500 is in the future though. Probably a little solar on the bimini down the line.


Whitall Stokes

Hi John,

The solar panel on the arch experience was on a Jeanneau 43 during a 600 mile race so comparisons were on display. I led the race on the downwind leg, then we had 300 miles upwind to the finish (Yes, I’m no gentleman). A sunfast 3200 and Tartan 41 (no arch) handily passed me and finished by a wide margin. Lots of variables during a race of course, but the leeway (and drag) was very noticeable as she heeled over in 10-25 knots. My tacking angles were on display on the tracker and ugly, looked like 110. The Jeanneau has a 6.6′ draft with and efficient fin and lead bulb.

On lithium, I’d be delighted to be talked out of it. Really. But I’m considering it for two reasons. First, AC loads will be increasing with Starlink (marine panel), watermaker, and washer (removing aft head). Yes, likely the watermaker and washer will be run with the generator running, but Starlink, autopilot, fridge will be ongoing draws. Second, I’d be able to expand useable capacity and improve charge acceptance from a gallon of diesel, provided I match charge capacity to the generator and bump up the alternator output.

The M&R56 has wonderful capacities for diesel, propane (4 tanks!), freezer & frig. The limitation is the water tanks at 260 gallons, especially with inexperienced guests. With a watermaker and more efficient charging from both the alternator and generator she will be even more self-sufficient.

Funny how expensive Starlink turns out to be. Not really a choice if I want anyone to join me out there. So yeah, talk me out of it. Hope this isn’t too much thread drift.

Melissa Dixon

I live on a Waterline 38 with 200Ah of lithium house bank, 200W of flexible solar mounted on our hard dodger (one panel is frequently partially shaded because of the boom but we have no arch and minimal safe options to place them on deck). Normally we live out at anchor for the entire summer, and in a marina during the winter (so plugged into shore power) but we will usually go the entire summer without being plugged in once. Due to the long summer days in the PNW that have been incredibly dry and sunny the past couple of years, those 2 flexible panels make more than we need, and that’s despite us having a fridge and mini freezer that’s front opening, and 2000W inverter for a laptop, blender, etc. Granted our use is pretty minimal in some regard as we don’t yet have an autopilot, no watermaker, AC, etc. And cook on propane.

95% of the time in the high season this repower works for us (I haven’t even installed the DC2DC yet since we have been in safe waters with civilization closeby, but I wanted to get cruising during summer months instead if sitting on another project). So that means no alternator to the horseback either.

However, when we were up in Desolation Sound, we got 3 days of monsoon like rain, with heavy cloud cover, and that definitely chewed through our battery bank. We managed to hold on by being careful, and eventually hit a sunny day, but we’re having a hard time “getting ahead” with topping up the batteries. So I decided to install the 100Ah folding solar suitcase I had bought and put of installing (but had bought all the necessary wiring for), and while we were waiting out a gale on Hornby Island, installed it. And HOLY that thing CRANKS out amps. Between the partially blocked flexible and the suitcase, we were charging at 10Ah! Plenty for little old us. It’s great because we bring it out and plug it in on anchor, and then tuck it away in our sail/rope locker when out and about.

In the next year or so we are hoping to do more shoulder season cruising as often there is better, more consistent wind for sailing, less hot and way less people, but of course shorter, cloudier days. So it will be interesting to see how our solar renewable stand up to this (I suspect not well). Will definitely warrant the installation of the DC2DC for that alternator umph. And since we day hop usually every few days between anchorages which always involves at least a bit of motoring, I wonder if it will be enough.

Paul Borondy

Hi Melissa,
Your system is slightly smaller than mine, this is what I do for overcast conditions: When abundant power is available, cool your freezer down to maximum. Mine goes to minus 18, then when expecting multiple overcast days, change the temperature to around minus 7 degrees. Everything will still stay frozen and the freezer will cycle less often.

Simon Robinson

Here’s something eccentric. We have a methanol fuel cell on board. Ours is a bottom-of-the-line 40 watt Efoy – giving us 80Ah a day at 12V – connected to a 5 litre (1.3 US gallon) cartridge of 5.6 kWh capacity.

Negatives. Methanol is yet another fire risk (and toxic). The cartridges are eye-wateringly expensive and the cell warranty depends on using Efoy’s non-refillable fuel cartridges. The cartridges are also expensive to ship because of the carriage safety requirements. They are virtually impossible to find if you cruise widely. I don’t think that their methanol has a renewable manufacturing process.

There are positives. To Efoy’s credit their cartridges are robust and leak-proof, even when you swap them at sea. The whole setup fits in small spaces below (ours is on a shelf in the pilot berth), is an easy install, requires little ventilation, operates on a heel, activates automatically, isn’t overly warm in operation, and the exhaust is ‘safe’. The unit is virtually silent and can run continuously for days without intervention.

I’d struggle to say there’s any overwhelming case for this over anything more conventional covered in these articles. It made more sense on our old trailer sailer which had no deck space and low power needs. BUT…

It is our get-of-jail card on our larger 34ft boat. On our last grey and stormy 2-week passage, we lost our engine a week in. We had a year earlier removed our Rutland windgen as heavy, noisy and redundant compared to just using the alternator (a removal I felt guilty about before reading these articles!). Our solar is sometimes enough in good weather (220w) but there isn’t room for much more, even if we built an arch. But on this occasion, we turned off the fridge, ate the contents, and then (quietly) chewed up methanol for the rest of the passage. At that point I don’t resent the $60 USD cost of the cartridge or the bulky box taking up the shelf space.

The units scale up to 75w and 125w versions within the same footprint, if you need a kick instead of a trickle.

Matt Marsh

It’s possible, it’s just a question of trade-offs. I’ve seen plenty of boats that are festooned with solar panels plus a big wind machine above that, never plug into shorepower, and rarely run their engines for long. For a liveaboard who spends most of their time docked or anchored, and is never in much of a hurry to get someplace, that’s an excellent solution.

On a boat that spends more time underway and is trying to keep to a tighter schedule, the added weight and windage of that equipment is significant – often enough, as John’s pointed out, to compromise sailing performance and cause the boat to spend more time under engine than it ought to. Here, a really good alternator setup to extract as much juice as possible from each drop of fuel during times when you’d have no choice but to be motoring anyway is a pretty easy solution to justify on both engineering and environmental grounds.

David Westcott

All very interesting. We have taken a slightly different approach and have chosen to go with renewables. We have done so in a way that, I think, makes a good compromise in terms of your concerns about windage and weight aloft for solar panels.

We have a canvas bimini. Though we have just spent the summer in Svalbard and Norway’s arctic coast, most of our cruising will be, and our home port is, in Australia’s tropics. In our opinion, in the tropics comfort and health considerations make a bimini a requirement not an option (though to be honest, we found it to be no less useful in the arctic).

On the bimini we have mounted four 116W carbon fibre-backed flexible solar panels (specifically designed for use on biminis and dodgers and with a reported efficency of 23%). These weigh 2.8kg each and so for an additional weight of 11.2kgs above our heads (plus the wiring, let’s call it 11.5kg) we have 464W of solar. This set up had no trouble keeping up with our usage in the arctic, despite weeks of grey, rain and fog, so long as we only used the autopilot while motoring (our Windpilot vane did the steering trick for us while we were offshore and we hand steered in coastal areas if things got too tricky for the vane).

While there is no argument that this arrangement doesn’t help the sailing performance of the boat, particularly on a centre-boarder like ours, under most conditions this was something that we could live with and really required just a bit of grumbling to feel better about. 

However, when conditions require, we can unclip each of the panels (six buttons each plus the two cables) and take them below to stow in the aft cabin while the bimini is closed and lashed shut and out of the way. All up it can be done in 10 minutes in less-than-ideal conditions. One might wonder whether such a setup is solid enough to withstand adverse conditions if isn’t disassembled but it does seem to be. On several occasions we had winds of 40kts with higher gusts where we didn’t take everything down and it all fared just fine.

A compromise to be sure but its seems to be a reasonable one.

Paul Y

We have refitted Razzle Dazzle (61ft Simpson daggerboard performance cat) with 5KW solar (3.4 rear carbon arch, 1.6 bimini) , 30kwhr 48v battery, 10kva inverters. Watermaking, hot water, refrigeration (220v), cooking and BBQ are all electric, no propane.
Backup is a 9kVA 56v 160A alternator on the port engine.
Backup backup is a 12v alternator
Backup backup backup is a Honda EU2200 generator

We can run all loads for 8 people on passage or a family of 5 with teens and no fuel used in nearly all circumstances.

Diesel heating available if far north in winter.
One AC unit can run 24/7 in summer on dock if needed.

Boat stayed 12v and we use the same type mppt for the panels as a DC-DC converter for common spares.

Its absolutely doable.

Paul Y

Never used the gennie once the solar went on. It was used during refit. I should sell it. Kept now to run 220v flood pumps.
The APS 9kw alternator is plenty of backup

My tips for other boats would be ~2-3kw is plenty without teens and likely 1.5kw solar if you conserve just a little and stay in the tropics.
Cats have so much unused space at the back that maximising solar is cheap and doesnt impact sailing. The whole 3.5kw arch is 55kg + panels.
The BBQ and Oven use plenty of power, as does significant watermaking. The advantage of water and hot water is you can time both somewhat for optimal weather.
Extra battery capacity is nice to get though a couple of down days, or just run a big alternator that decently loads the engine for efficiency. 48v is ideal for this.
I’d have less MPPT’s next time and use EVE cells as they are more compact than Winston.
A single 8 or 10kw victon inverter is outstanding for intermittent heating loads like cooking and instant hot water.

Paul Y

The LiFePO4 is amazing and when using a solenoid based BMS in my view far safer, more reliable and cheaper than LA.
The ability to use much of the battery capacity cycle with heavy loads is wonderful.
I dont see significant additional complexity or failure points.

Steve Holloway

I can’t agree with the general conclusion here as it certainly hasn’t been my real life experience.
We have been live aboard cruisers for 7 years now and our boat originally had a top end on board generator fitted which I estimate would have cost about $25,000 to install. It was nothing but trouble! It was apparently the second unit in there as the first was so bad it was replaced under warranty. I spent more time working on the second one than any other part of the boat & we eventually pulled it out.
It was the best thing we ever did.
We had had it for 3years by that time and learned that with adding solar and good Balmar alternator we didn’t really use the generator anyway.
We live at anchor full time in the summer and for the last few years have been in a marina for a few months over winter as we are sailing in the Med.
To be clear I don’t disagree with most of you working out, just with your conclusion. This is why.
You’ve left out a BIG disadvantage with a genny… you have to run it!
We don’t sail to lovely isolated bays to run a bloody generator! Yes a good one is pretty quiet, ours was, but we still hated running it.
With the right boat for cruising and for me that’s a centre cockpit, you do have room for a decent arch. The best thing to use are modern bifacial panels, about 30% more per area than mono facial ( that’s what they claim and it’s true, we’ve had both) by the way I’m not sure where your figure of $6500 for solar comes from, we’ve just bought a 525watt bifacial panel from LG who are one of the best for €400. We don’t notice any more pitching or problems sailing but I agree that depends on the boat. If you want to cruise in a fast lightweight boat then thus could make a difference I’m sure.
For us when we got rid of the generator which was nicely in the middle of the boat we put lithium house bank in its place and ripped out the 3 massively heavy AGMs which were in the aft cabin so I think we’ve more than made up for weight aft if not windage.
I’m really not sure the windage is making any difference with our boat though, I was actually thinking more windage aft might act as bit of a riding sail at anchor but I haven’t noticed a difference.
We have several fold out panels for use at anchor. A 400w panel that goes over our upturned dinghy on the fore deck and a 200w foldout bifacial panel that clips to the guard rail and gets hauled up with a halyard, this way it’s on the outside of the boat do doesn’t get in the way and it gets reflected light off the sea. I tend to charge Ecoflow generators with these, another topic perhaps but a good way to help with energy.
We have no wind genny. as you rightly point out they are not worth it especially if you have solar because of the shading.
I am worried about long passages with our set up though, we will be crossing the Atlantic soon so need to have something in place. That may be a wind-vain or a bigger alternator or both. Our usual cruising speed is a little low to get the most out of hydro.
But the point is we have been full time cruising with no genny for 4 years now and with our boat at least we are much better off than when we had a generator in every way!

Derek Ratteray

Hi John,

There’s good case for having, at least, a small amount of solar if you have lead batteries. It will help get them to float and keep them there, which cannot be a bad thing.

I started with 100 watts some years back. They weren’t ungainly at all. It really helped the batteries stay happier. That was replaced with 5 panels (575 watts in total) that sit neatly on my bimini, which is deployed at all times anyway. (I have never understood why sailors insist on being exposed to the elements getting burnt and drenched alternatively anyway.)

In addition, I have a Superwind 350 turbine, which is virtually silent. How do I know it’s quiet? Because people are constantly coming up to me and commenting on that. It’s not just my hearing.

I say all that to say this. I have gone from running my genset 3 hours per day (morning and evening) in BVI to running my engine (170amp alternator) for an hour or so every couple days at anchor, which I must do for hot water anyway.

I figured that running my genset that much was the equivalent of driving a ICE car 30 plus miles per day, which conflicted with my desire to be more green.

I had my Northern Lights genset removed and I donated it, at considerable weight savings – which has hardly been equalled by the addition of my turbine and panels. The boat sails as good as ever.

My message is try it. You might like it. Every little bit helps to burn less diesel, which cannot be a bad thing for our children.


Dick Stevenson

Hi Mal,
I have been a huge fan of the idea of a DC generator for decades: I say idea because I have yet to find a commercial DC genset with a good track record that can go into small boats.
I had a 15+-year run with an Ample Power DC genset (Genie) that worked great when it worked, but was a continual hassle.
I know of 3 Fisher Pandas that drove their skippers to distraction (and tried to turn them into paupers) and eventually were thrown overboard and turned into moorings.
Much research a few years back had one contender from FL, but the owner/designer was very weird to deal with, would not tell me how many were out there nor to talk with an owner with experience etc. Hamilton Ferris had a DC generator, I almost went for, but finally decided to go in another direction. I also looked at Polar but can’t remember why I did not pursue it (I think it was too big for the space I had to offer).
I know of enterprising and knowledgeable skippers who have taken a Kubota tractor engine and slapped a big alternator on it and made it work, but that was a stretch too far for me.
I still think the idea is great and it does not seem like it should be rocket science: but I suspect the market is small, perhaps very small.
My best, Dick Stevenson, s/v Alchemy

Derek Ratteray

Hi John,
To be clear, it was 3 hours, in total, for my daily running time – just split half in a.m. and half in p.m.