Why choose DC (Direct Current) over
AC (Alternating Current) when Selecting a Generator?


As every sailor gets their boat ready for a cruise they think - hmm, "Should I get a Generator before I leave?" A Generator's primary purpose is to bring "shore power" along. Choosing a Generator can be as easy as going to a hardware store and buying a non-marine unit or buying a proper Generator that has been designed for the marine environment. The main purpose of a Generator is to maintain your batteries. After that it becomes a luxury to be able to enjoy the use of your 120Vac tools, appliances like a microwave oven, and even air conditioners. Remember, the main function of the Generator is to charge your batteries.

The Power Glitch and Charging Run Time requirements - Standard shore based "city power" produces a significantly cleaner sine wave power output than any 120vac Marine Generator is capable of producing. This enables the vessel's DC charger to operate at 100% of its capacity at best efficiency. As you operate that same charger in your vessel off of the installed 120vac Generator, the battery charger's operational efficiency drops to as low as only 30% of what it had compared to its operation back at the dock on shore power. Additionally, when you use an AC generator to charge batteries through a battery charger, it will require a significantly longer run time due to the limitations (current output - amps) of most battery chargers - and that is even if it were 100% not 30%. ZRD's DC generator can produce significantly more 100% clean charging current than an AC generator system using a battery charger. With a ZRD DC generator and a properly sized battery bank you can have all the AC power you want and an efficiently charged battery bank with very little engine run time.

The AC Generator - In the current marine environment, most generators supply 120vac output. In order to charge a battery, you had to have a battery charger connected to the Generator. Any time you wanted to use 120V power, especially High Load items such as air conditioning, most start their Generator. All Generators create noise and consume precious fuel. All 120vac Generator must be run at their designed full throttle rpm setting (manufacturer determined) in order to function. That means it is using maximum fuel - all the time. This is especially critical when it comes to generating the required frequency (60Hz) for all 120vac electronics to function properly without a loss of efficiency. Some may even stop working if 60Hz is not available. Even if 120vac and 60Hz are produced, it will not be as clean enough for many of the electronics being used to operate at better than 50% efficiency. Typically, they are also oversized when operated only to supply charging requirements. Again, creating additional noise and wasting more precious fuel.

The DC (direct current) Generator - Have you considered or are even aware that DC Generators are available? They are a great solution to the noise, fuel consumption, and less than stellar output of an AC (alternating current) Generator. DC Generators are rare. New to the market is a breed that does this with the most thoughtful of designs. Specific Engines are matched with DC production (voltages - 12, 24, 36, 48, amperages - 90, 180, 200, 220, 330 ...) as a balanced pair to ensure the exact fit to each cruiser's needs. DC Generators eliminate the 120vac "Power Glitch" and always supplies a clean 100% ready source of charging power. This ensures the ship's battery bank is always ready to go. When using a properly designed 12vdc Generator, its throttle may be adjusted for more or less power, depending on the demands placed on it (load) by charging or other user needs. This is no different than using the gas pedal in your vehicle. The 12vdc output is operating at 100% of its efficiency delivering the correct voltage and amperage necessary for proper battery bank charging and operational use.

What about your 120vac needs? - We all want to run our microwave, air conditioner, wall outlets, etc. It is a snap and part of a ZRD easy solution. We supply or you may already have an inverter to operate with the DC (Direct Current) Generator. With a properly sized battery bank combined with an inverter, cruising with a ZRD Generator Solution becomes a pleasurable experience.   5K Inverter

An inverter uses the ship's battery bank (typically 12vdc) as an input source of power and converts it into 120vac that you may use directly without the need for any engine to be running! No more noise. Additionally, you may routinely run your air conditioner overnight on your batteries without the danger of running an unsupervised engine. It is possible in Florida during the summer 90+ degree evenings to do this and consume less than 200 to 250AH in an 8 hr overnight period (includes initial daytime heat sink cool down period) running a 16KBTU A/C. How do we know? We do it when cruising.
220amp DC Generator

DC vs. AC Generator
Some differences between DC & AC power production and use.

An important factor that enters into every discussion - COST. Depending on size, the typical 120vac Generator will cost apx. $15,000 to $20,000 for purchase and installation. In addition, the corresponding inverter/charger adds an additional $5,000 charge. One may reduce costs by installing a charger only for apx. $1,000, but inverter function will be lost requiring 120vac Generator operation for all 120vac requirements. Total expenditure is $20,000 - $25,000.

ZRD DC (Direct Current) Generator solutions start at $8,057.15. One of these will surely fit your needs (and the entire cruising community). Including some required minor installation requirements, and an inverter a total ZRD 12vdc Generator solution installed will cost apx. $10,000 less than an installed 120vac solution.

The ultimate decision always rests with the cruiser and his best judgement. After reviewing the differences discussed, the choice appears to be straight forward and obvious. You should be able to come to the same conclusion ZRD has in its decision to finally manufacture and make available to the boating community the best DC (Direct Current) Generators available, bar none! It is a wonder very few DC Generators, especially good ones, have been available until now. After reviewing all of the information presented, you should be better able to decide what type of generator is right for you, your requirements, and needs.

A "Conversation regarding cheap portable generators" is at the bottom. For the typical ZRD customer, it is something they already know and do not need to read, but it explains how and why Wal-Mart has grown over the years.

Because PRICE is usually the First or Second Question asked, YOU should Seriously Consider the following.

Depending on your usage, the Net Cost of a ZRD DC Generator may be   $0.

Depending on your usage,  the Net Cost of a ZRD DC Generator may be $0.

For additional information, Contact ZRD
and have us custom manufacture a DC (Direct Current) Generator to fit your needs and requirements.

To not clutter the article above with some raw data, informational input is shown below for the just have to know tech types.
• Largest boat dedicated charger available (12vdc - 60amp) produces only 30 amps (apx.) of charging power when run of off the boat's 120vac generator.
• Largest boat dedicated inverter/charger available (12vdc - 150amp) produces only 80 amps (apx.) of charging power when run of off the boat's 120vac generator.
• ZRD dedicated DC Generator produces 220 amps @ 12vdc in example, but it is available in many other voltages and amperages.
• ZRD dedicated DC Generator solutions do not require additional equipment in order to charge batteries or power large DC Loads.
• ZRD dedicated DC Generator solutions may produce up to 6,667% more amperage available for battery bank charging (1,250% for largest inverter/charger available).
• The ZRD ZDCGE1222 Generator solution typically requires only 7% of the engine run time a 30amp boat charger requires in order to charge (36% for 150amp inverter/charger).
• A simplified overview of the above may be explained in the following 2 examples:
  » A ZRD DC (Direct Current) Generator vs. a Standard 120Vac (Alternating Current) Generator has a 10 to 1 run time efficiency for typical overnight air conditioning use. Next, a ZRD DC Generator vs. a Standard 120Vac Generator has an apx. 4 to 1 run time efficiency for fuel consumption. The Resultant Total efficiency is up to 40 to 1 now. If you were to have a larger oversized AC generator (like many do), this number may easily exceed 100 to 1. Add in ZRD's forward thinking throttle control, and efficiency soon doubles (200 to 1) or triples (300 to 1) by not needing to run a generator at full RPM all the time. AC generators have no option to do this feature - They MUST BE RUN at FULL RPM whether 1% or 100% of amperage output is required.

» While cruising at anchor, charging the house battery bank using the installed standard shore charger running on 120Vac power supplied by an AC Generator (no shore power available) it has an efficiency reduction of 9 to as low as 25 or more to 1 compared to when that same charger is powered via Reliable Good sourced 120VAC shore power. Now, add in the engine run time required 1hr (DC Generator) vs. 3 or more (120Vac Generator) and the efficiency comparison changes to 27 or 75 or more to 1. Don't forget the apx. 4 to 1 run time efficiency for fuel consumption and the Resultant Total efficiency for comparison may easily reach 108 (or even up to 300 or more) to 1.

• The current battery bank condition (not charge state) is an item one always needs to be aware of and is one of the most misunderstood situations. Regardless if the batteries are old or new, but are worn out from improper charging or maintenance, they will not be able to handle any load beyond a few amps. A small load of a few amps (10-25) is usually possible from a dead battery bank for many years after the batteries have died. However, if a large load is applied, the batteries will immediately notify the boat operator that the batteries are in fact dead and are unable to supply the required higher demanding load. This is why the only way to know if your battery bank is still good is to have an installed battery monitor (gives months of advance notice) and test it regularly with an actual load meter. See the following FAQ that shows a load meter.

A Conversation regarding cheap portable generators.

Since the ZRD DC (Direct Current) Generator was introduced, we have received wonderful reviews and feedback. Although in a very small minority, we have received a few questions similar to the following. Read their thoughts and our view regarding the underlying fundamental principles on different ways to approach a solution.

I read the ZRD FAQ on "Why choose DC (Direct Current) over AC (Alternating Current) when Selecting a Generator?". The case you put forth makes sense for traditional AC diesel generators. It does not address the Honda series which is what everyone seems to be going with. I have one even though I'd much rather have a built in diesel. Sure, they are not marinized, but they're inexpensive and they work well. I would love to be able to just turn on a switch and run a generator, No pulling cords to start, rigging shore power cords, etc., filling gasoline tanks and schlepping them around. The Honda uses more fuel than my dingy. I just wanted to let you know that ZRD is missing a significant portion of the cruising community by ignoring the Honda phenomenon.

Addressing "ZRD is missing a significant portion of the cruising ..." For any community that is willing to sacrifice on important, significant issues strictly over price, ZRD's choice would be to bypass that community. ZRD will never provide an inferior solution in order to generate revenue - ever. ZRD always strives to provide the best proper solution or none at all. We have passed and will continue to pass on prospective customer opportunities in order to not have our name attached to an inferior solution they desire ZRD to manufacture or provide for them. We frequently tell customers that ZRD operates like the original Motorola from many years ago. Their company philosophy had at is root, "99% is not good enough". Look what happened to them when they compromised on quality just in an attempt to "compete on price" alone. The ZRD community understands our philosophy - "You Deserve Us".

In addressing the Honda scenario, the prospect made the direct case for us logistically on why not to use a portable generator in his own email. We do not need to expand on that any further, but if you understand how inefficient an AC Generator is, just observe how much less efficient than even that your boats 30 or 60 amp charger is when running on a Honda. Unfortunately, the most significant item he did not see at all and completely overlooked (because they are always blinded by price) was Safety. We have not mentioned safety directly for the same reason. It is so obvious, significant, and the backbone of everything ZRD does. ZRD will NEVER COMPROMISE on anyone's safety. This is a line in the sand for us - e.g. when a prospective customer wants an alternator for a gasoline engine without a spark arrestor or operates a generator all night with no one monitoring in case a malfunctions occurs that will endanger lives. The same mentality that will accept using a portable gasoline generator on a boat is the same thinking that does not wait 5 minutes for it to cool down before refilling when it runs out of gasoline. It probably ran out unexpectedly due to its not being monitored. I am sure they also only use it in calm conditions because it is as stable as being on land - NOT, even on a cat, ... I can go on, but it is apparently nothing they desire to hear, so why continue. Those of us that know, do not just do it, but Do it Better.

His and a few other emails are now addressed. This is an example of someone attempting to justify their "Wal-Mart" thinking - Cheaper wins over proper solutions. In the bigger picture and long run, ZRD solutions are the most economical when ALL factors are considered. This is the underlying problem in corporate business today. Any company run by an accountant(s) instead of a CEO that has a verifiable operational background and truly knows what he is doing is usually producing inferior products and is doomed to eventual failure. They do not know how to think or make decisions outside of a spreadsheet. They are incapable of incorporating intrinsic values and costs into it. Those costs and benefits are not easily quantifiable by accountants, but are known and valued accordingly by ZRD. ZRD will Never compromise on Quality or our customer's safety.

The case for a 120Vac Generator?

The answer is simple - If you desire or use your vessel as a Floating Condominium forever on the hook, never at a dock, used very little on the open water, continually consuming an inordinate amount of electricity to run all types of items and HVAC, with limited or non-existent supplemental solar and wind sources, have an unlimited expense ($,$$$,...00) budget, have an unlimited continual access to diesel fuel, and have no concerns about the environment, wildlife, or climate change, then a 120Vac Generator may be the solution you should choose.

The difference between the two sources of electrical power is in the total time and amount of power consumption you will require per day - 400Ah vs. over 1,000Ah. To meet these non-cruiser higher consumption needs with a 120Vac generator, daily run time durations of 16 to 24 hours are required with its associated 15-25 gallons of daily fuel consumption, cost$, maintenance, noise, and obvious safety concerns.

ZRD manufactures DC Generators for most situations. If you have determined that you "need" a quantity of electrical power that is beyond what the majority of "standard cruisers" use, even after you have added supplemental electrical power in the form of solar panels and wind generator(s), you may seriously need to consider installing the ZRD model ZDCGEUR (4Kw) DC Generator instead of the usually selected ZRD model ZDCGE1222. This enhanced output model allows for continuous unlimited run time operations (similar to a 120Vac Generator), but without the extreme higher operating costs. And for those times that unlimited run time operations are not required, it still has all of the advantages of a standard ZRD DC Generator. For very large vessels (over 50' in length, typically over 60' or large catamarans) the ZRD DCGDI2440 may plainly be your solution of choice. Again, in ZRD's opinion, installing or using a 120Vac Generator should only be done in very limited situations.

Generator or Genset?

The words Generator and Genset are often used interchangeably. A generator or genset, consists of electricity production components (typically a DC Alternator or AC Generator) combined with (connected to) an engine that provides the necessary rotational energy required for the electricity production components to produce their electrical output. This combination of components is called an engine-generator set, gen-set, or genset. Most commonly, the engine is assumend and taken for granted resulting in the combined engine with its electricity production component being called a generator. DC or AC is added for additional clarification as to which type of electricity is being produced.