right boat generator size

How To Select A Right Size Generator For Your Boat

Find Right Size Generator For Your Boat

Selecting the right marine generator for your boat is one of the crucial aspects of the purchasing decision. To get the best results that meet your specific requirements from a generator set, some factors and considerations must be fulfilled.

Marine generatorYou will need a marine generator that offers longevity, be reliable and can deliver comfortably for long working hours.

Unfortunately, determining an exact generator set that is suitable is never an easy job. Therefore, this article offers a guide to choosing the right boat generator size.

This will familiarize you with some generator terms and provide you with the basic understanding of the various boat generators.

How Much Power You Require For Your Onboard Utilities

Walking into boat generators dealer and buying the cheapest or the best generator available without any prior knowledge of your power requirements is not the best approach.

To begin with, determine the total power of all your electrical equipment on your boat by adding up the power ratings usually indicated on each of your gear’s nameplate.

You can also be able to determine your energy consumption for a given day in kilowatt-hours if you are using an intelligent battery monitor. Keeping track of your power consumption for a month or two before making any determination on your power usage is a good practice.

If your lifestyle involves walking into your boat and switching everything at once, then the best generator size to choose is one with a rating of 20% more than the total score calculated.

However, if you lead a moderate lifestyle where you regulate your power requirement by switching on only the necessary equipment, you can then opt for a smaller sized generator set.

With the advancement in technology, marine generators are now available in various range of sizes, for example, gen sets with rated power supply capacities of 5kw to 50kw are readily available in the market. If you choose a lower size boat generator, you most likely run the risk of overloading it and hence compromising on its efficiency.

Some Of The Terms You Need To Know

Power is represented by a unit named Watt (W) which is a product of 1 Amp and 1 volt i.e. (Watt=1Amp x 1Volt), and 1000 Watts makes up 1kW. Ordinary generator sets usually operate at 230v therefore based on the current rating of equipment; the power rating can easily be calculated.

You may have at times noticed that some manufacturers quote their electrical products in KVA, this is known as an apparent power, which usually applies to resistive loads and the relationship with KW is based on a normal convention called power factor.

The power factor ranges from 0 to 1 but usually given as 0.8 in most gen sets; therefore, power in KW is calculated by KW=KVA X 0.8. From this relationship, you can comfortably calculate your gen set’s power in KW if it’s rated in KVA. It is also an important practice to consult an expert to confirm that your size calculations are right before purchasing a boat generator.

Other Size Determining Factors

Once you have determined exactly how much DC or AC power you require for your utilities, it is now straightforward to choose the right sized boat generator.

If you are using a DC generator to recharge a battery bank and you already know your DC power consumption in Kilowatt hour, you will want to be economical and minimize your gen sets runtime.

A real runtime target for your generator may range from a half an hour to about 2 hours run depending on the type of batteries you have. AGM type batteries can get charged a lot faster as compared to the traditional standard flooded lead-acid batteries.

Supposing you need to replace 7KW of DC power every day with a 2 hours runtime, for example, then you will require a generator set that can be able comfortably to generate 3.5kw of power (3.5kw x 2hrs=7kw hrs).

But if you are running your AC equipment and charging your batteries at the same time, then you should ensure that the generator you choose should have the capacity to run them both at the same time.

All you have to do is to add the AC load to the DC load to get the power rating of the generator you will need. For example, if your AC power requirement is 2.36kw and DC requirement is 3.6kw, then we will have 2.36kw + 3.6kw=5.96kw.

Generator Set RPM

This refers to revolution per minute (RPM) of the generator unit. Depending on the size of your boat you should also put this into consideration. When a boat generator is run from a start, it ultimately comes to its rated voltage and frequency, for example, 50Hz at 1200 rpm.

For most generators in the market, this speed varies from 1500, 3000 or 3600rpm based on each design. It is important to note that low-speed generator sets such as the 1500rpm are large and heavy and are often not suitable for leisure crafts.

The 3000rpm models are the most commonly used generator sets since they are fuel efficient and quiet although they are slightly bigger and costly. The high-speed generators such as the 3600rpm model are more economical to buy and may provide more power with smaller crafts. However, it’s high revving increases noise and does not last long enough.

Travel Power Generators

This type of generator utilizes the power of the propulsion engine. They are mounted on the boat’s engine, and its power will depend on your boat’s engine speed.

The power of the travel control onset increases with increase in engine speed; full output is achieved at a rate of the 1600rpm-cruising speed. It is a compact solution for generating power to run your onboard utilities.

12 Volt DC

The domestic battery banks provide this to power DC equipment on your boat. An inverter can be used to convert the DC power to AC for powering AC appliances on your boat.

This usually occurs in certain conditions for example if the power requirements of your boat are relatively small. However, if your boat has a high power demand with an electric motor, then you will have to opt for a marine generator. In fact, some cases demand that you have both the boat generator and an inverter.v