Selecting Your Marine Generating Set: Live Aboard Vessels

Beta Marine manufacture a range of small compact marine generating sets which are ideal for live aboard yachts and barges. These guidelines are hopefully an aid to enable you to calculate the size of Beta Marine generating set you require, and therefore the cost involved. What do you wish to power? There are two sets of equipment to be considered:

  • The mains powered items similar to those you would use on land where they are powered from the domestic mains.
  • The items that are powered from your batteries.

With a house or land installation the amount of power is unlikely to be problem because you will be connected to what is known in the trade as an “infinite bus”, in other words the national grid and there is generally as much electricity as you can afford. However a generator set is a different matter. It can easily be overloaded which will result in a reduction of voltage (less power), a reduction of frequency (Hz) (motors will run slower) and even stalling of the engine.

Your life style is also an important consideration – if you wish to be able to walk onboard and switch on everything at once then the calculation is straightforward, just add up the maximum ratings on the appliance labels / nameplates and you have the size required. If you are able to change your life style and moderate / schedule your electrical power requirements / loading by considering which appliance you are switching on and the power / load – plus possibly using one machine after the other – then you can happily install a considerably smaller generating set.

To help you decide what size of ‘mains power’ generator set you might need we suggest you fill in the following chart. Fill in two operating modes, mode 1, perhaps whilst cooking lunch and mode 2 whilst relaxing/general domestic, leave blank the items that do not apply. For example:

Appliance or Load Possible Rating Operating Mode 1
Operating Mode 2
Electric Cooker 5 - 10 kW    
Kettle 2 - 3 kW    
Water Heater (Immersion Heater in Water Tank) 3 kW    
Washing Machine 1.5 - 3 kW    
Tumble Dryer 2 - 4 kW    
Washer/Dryer 1.5 - 3 kW    
Microwave 0.5 - 2 kW    
Hair Dryer 1 - 2 kW    
Food Mixer 0.5 - 1.5 kW    
Toaster 0.5 - 1.5 kW    
Vacuum Cleaner / Hoover 0.5 - 1.5 kW    
Coffee Machine 0.5 - 1 kW    
Electric Hand Drill 0.2 - 1 kW    
Fridge (If Mains Powered) 0.1 - 0.4 kW    
Electric Blanket 0.05 - 0.2 kW    
Television and Video or DVD Player 0.1 - 0.3 kW    
Battery Charger / Inverter Charger 0.2 - 3 kW    
Air Conditioning System 2 - 20 kW    
Other -    
Total Load      

There are a few things that you will need to know

  • 1kW (kilowatt) = 1000W (watts). 1W = 1Amps x 1Volts. The volts are usually 230V for ordinary mains (AC, alternating current) supply. The amps may be quoted on the appliance makers label. If the kW, W or amps are quoted on the label you can enter the exact figures in the table.
  • You will not use everything at the same time and you should organise yourselves so that you do not. For example you should not need to use the Coffee machine when you are boiling the Kettle, or the Toaster when the Oven is on, etc.
  • If you cook by gas your generator set can be very much reduced in size. If you have an air conditioning system then it may need to be very much larger.
  • You can adjust your lists to suit your style / mode of living. The heaviest mode is the size of generator set that you will require.
  • To select your set you will need to know another relationship. Most makers quote in kVA. The relationship of kVA to kW is based on a normal convention of 0.8 (called the power factor) so that kVA x 0.8 = kW, or kW / 0.8 = kVA. So in our example 16.2kW = 20.25kVA. Select a BetaSet26 or adjust your mode of living and select a BetaSet 21 or BetaGen if you require an acoustic enclosure. This form can be ‘downloaded here’ and printed to create your list.

A few notes and comments that may help

To help you fill in your list you should find that each appliance has a label / name plate on it detailing the ‘ Stated Load’ i.e. maximum possible load,  generally on the back, or underneath and it is this figure you need to start with. Please note that most fridges on smaller boats are battery operated (DC, direct current).

  • A typical 60 foot Wide Beam / Dutch Barge may have: Electric oven, Washing machine, Tumble dryer, Fridge/Freezer and possibly air conditioning plus other smaller items.
  • A typical 35 foot Power Boat may have: Air conditioning, Electric oven, Washing machine, Tumble dryer, Fridge/Freezer fridge, electrical navigation equipment, lighting and water pumps.

If you buy a generating set that is too small you will suddenly become very aware of the electrical power you need, it is generally safer to err on a slightly larger size that allows for a safety factor and any electrical items you may purchase in the future. It may therefore be better to spend a little time talking to other people and getting the size calculation correct before you buy.

ELECTRIC COOKER: If you wish an electric cooker you need to consider the physical size and power when buying – a standard kitchen oven will generally have a 4kW oven and 4 hot plates from 1 kW to 2 kW each, totally about 10kW maximum possible load, and if you wish to switch everything on at once you need to allow for 10kW continuous loading. However it may be that the oven is set at 180°C and 2 hot plates are set at low and medium (all thermostatically controlled) switching in and out,  so the actual load may only be 6kW or less. A full Sunday lunch may push the loading up for a few hours.

AIR CONDITIONING: Varies considerably dependant upon the size of motor yacht / wide beam and it’s size can vary from 2 kW, up to 20 kW. You need the exact details of the installation and the manufacturer will supply you with starting current and running current details – if in doubt please ask us for help.

ELECTRIC KETTLE: Is powerful 1.5kW to 3kW, but only tales 2 or 3 minutes to boil.

FRIDGE & FRIDGE/FREEZER: If a mains powered fridge is selected it will need continuous power. This is normally via an inverter powered by your battery bank otherwise you would have to run your generator set continuously. Most fridges on boats are small and powered directly from the batteries. The generator set will have to power your battery charger or inverter charger and this should be taken into account when sizing. Usually the batteries are also charged from your main engine driven battery charging generators too.

WASHING MACHINE, WASHER/DRYER & TUMBLE DRYER: These require from 1 to 3 kW each and the cycle can take from 1 hour to 2 hours on load.

HOT WATER: We would always recommend that you fit a calorifier for hot water, heated by the engine cooling system when the engine is running.  This gives you ‘free’ hot water.

IMMERSION HEATER: This is generally a personal decision – if hot water is required then there are alternatives. A solution is an immersion heater and it is normally mains AC powered and 2.0kW, requiring either a shore line, Travel Power, or a Generating set

Having calculated / guessed the actual power you need, you need to add together the worst case scenario of the possible appliances that could be on at the same moment – providing you with the minimum level of comfort you require, and you may wish to plan for the future adding a small factor for any future additions.

Some questions you should be asking yourself are:

  • Which large electrical appliances can I use in sequence? The washing machine followed by the tumble dryer is logical. Can I leave the washing to later, after I have finished cooking.
  • Do I have air conditioning and can I turn it off while I’m cooking? A big Sunday lunch will require a lot of power. Basically the choice is yours, what comfort level do you want and how much extra is the next size larger or smaller - generally not that much.

Generators typically supplied by Beta Marine Ltd

If you ‘live aboard’ then you will need a BetaGen with an acoustic enclosure; noise is a very important issue when living right next to the generating set. We also sell good quality ‘Sound deadening’ material at reasonable prices. We have found that some customers who moderate their electrical loading and sequence their appliances / electrical load reasonably - often consider the following:

Small Narrowboat: With only interior lighting, a television, microwave and a fridge, you need a suitable domestic battery bank and an inverter that is charged by the propulsion engine during the day, possibly a Travel Power 3.5kVA.

Narrowboat 60 foot: With 3kW Washer/Dryer, TV/Video player, 0.2 kW DC Fridge, 2kW Electric Kettle, Microwave, Shower pump, inverter charger – we often supply a 3.5kW or 5kW Travel Power mounted on the propulsion engine.  If you have the space – maybe a small BetaGen.

Wide Beam / Dutch Barge: With small electric cooker, 2kW Washing machine, 3kW Tumble dryer, 2kW Immersion heater,  0.5kW Fridge/Freezer plus television, video player, battery charger – such customers often specify a 1500 rev/min BetaGen 7 or BetaGen 10.

Sailing Yacht 25 to 35 foot: With 0.2 kW DC fridge, microwave, electrical navigation equipment, lighting, water pumps, inverter charger – we would recommend a suitable domestic battery bank and possibly a Travel Power driven by the propulsion engine.

Sailing Yacht +60 foot: With 0.2 kW DC fridge, electrical navigation equipment, lighting, water pumps, battery charger (possibly air conditioning) – customers have taken BetaGen 4/2 or BetaGen 7.

Power Boat 34 foot: With Air conditioning, small electric cooker, 0.2 kW fridge, electrical navigation equipment, lighting and water pumps – maybe a BetaGen 7 or 10

Power Boat 40 foot: With Air conditioning, small electric cooker, 0.2 kW fridge, electrical navigation equipment, lighting, water pumps, battery charger – perhaps a BetaGen 10 or Beta 11.

You will probably also have 12 volt DC (direct current) electrical loads. These are usually powered from the domestic battery bank and battery charger (or inverter charger):

  • Interior electric lights
  • Fridge
  • Navigation lights
  • Anchor winch
  • Domestic water pumps
  • Navigation equipment
  • Fans for diesel heating system and ventilation

Beta Marine Ltd offer the following:

3000 rev/min Generating Sets: are more economical to buy, but you will need to consider that they operate at a faster speed and will be noisier. They generate 230 volts AC 50Hz electrical power.

1500 rev/min Generating Sets: are the ones to choose for long life and steady reliability with lower noise levels but they are slightly bigger and more costly. They generate 230 volts AC 50Hz electrical power.

Travel Power Generators: are fitted to the propulsion engine and are very compact. There are two options 3.5kW or 5.0kW (and generate 230 volts AC 50Hz electrical power).

12 Volt DC: electrical power is from your batteries, you can have a large ‘domestic’ battery bank that will provide 12 volts for all 12 volt appliances – fridges, electrical navigation equipment, lighting and water pumps and can also power an inverter for 50Hz AC for a television etc.

We can offer both heat exchanger cooling, or alternatively keel cooling normally for canal boats. If you have any doubts at all, please ask and we will try to help. Correctly sizing the generating set is your responsibility – and we do not accept any liability if you use these guidelines. Beta Marine Ltd also produce much larger generators up to 1000kVA for seagoing ships etc.

Generating Sets: 50Hz, 1500 rev/min

BetaGen Model Max. kVA Output 4 Pole @ 1,500 rpm kW Volts
Maximum Load
1 Phase 3 Phase
BetaGen 7 7.2 - 5.7 kW 230 V 24 Amps
- 7.2 5.7 kW 400 V 8 Amps
BetaGen 10 9.7 - 7.7 kW 230 V 33 Amps
- 10.1 8.0 kW 400 V 11 Amps
BetaGen 11 10.7 - 8.5 kW 230 V 36 Amps
- 11.2 8.9 kW 400 V 12 Amps
BetaGen 12 12.3 - 9.8 kW 230 V 42 Amps
- 13.0 10.4 kW 400 V 15 Amps
BetaGen 14 14.0 - 11.2 kW 230 V 47 Amps
- 14.5 11.6 kW 400 V 16 Amps
BetaGen 17 16.0 - 12.8 kW 230 V 55 Amps
- 17.3 13.8 kW 400 V 20 Amps
BetaGen 21 19.8 - 15.8 kW 230 V 68 Amps
- 21.1 16.8 kW 400 V 24 Amps
BetaGen 26 25.3 - 20.2 kW 230 V 87 Amps
- 26.2 20.9 kW 400 V 30 Amps
BetaGen 33 32.0 - 25.6 kW 230 V 111 Amps
- 33.5 26.8 kW 400 V 38 Amps
BetaGen 40 38.5 - 30.8 kW 230 V 133 Amps
- 39.6 31.6 kW 400 V 45 Amps
BetaGen 49 44.0 - 35.2 kW 230 V 152 Amps
- 49.5 39.6 kW 400 V 57 Amps

Generating Sets: 50Hz, 3000 rev/min

BetaGen Model Max. kVA Output24 Pole @ 3,000 rpm kW Volts
Maximum Load
1 Phase 3 Phase
BetaGen 4/2 4.0 - 4.0 kW 230 V 16 Amps
BetaGen 6/2 5.7 - 5.7 kW 230 V 24 Amps
- 7.7 7.7 kW 400 V 11 Amps
BetaGen 11/2 11.2 - 8.9 kW 230 V 38 Amps
- 12.1 9.7 kW 400 V 13 Amps
BetaGen 22/2 22.0 - 17.6 kW 230 V 75 Amps
- 23.1 18.5 kW 400 V 26 Amps
BetaGen 25/2 24.8 - 19.8 kW 230 V 85 Amps
- 25.9 20.7 kW 400 V 30 Amps

Generating Sets: 60Hz, 1800 rev/min

BetaGen Model Max. kVA Output 4 Pole @ 1,500 rpm kW Volts
Maximum Load
1 Phase 3 Phase
BetaGen 7 7.1 - 5.7 kW 120 V 47 Amps
- 7.8 6.2 kW 220 V 16 Amps
BetaGen 10 9.8 - 7.8 kW 120 V 65 Amps
- 10.5 8.4 kW 220 V 22 Amps
BetaGen 11 11.2 - 8.9 kW 120 V 74 Amps
- 12.3 9.8 kW 220 V 25 Amps
BetaGen 12 13.5 - 10.8 kW 120 V 90 Amps
- 14.6 11.6 kW 220 V 30 Amps
BetaGen 14 15.0 - 12.0 kW 120 V 100 Amps
- 15.2 12.1 kW 220 V 31 Amps
BetaGen 17 17.3 - 13.8 kW 120 V 115 Amps
- 18.7 14.9 kW 220 V 39 Amps
BetaGen 21 20.0 - 16.0 kW 120 V 133 Amps
- 22.0 17.6 kW 220 V 46 Amps
BetaGen 26 27.0 - 21.6 kW 120 V 180 Amps
- 27.5 22.0 kW 220 V 57 Amps
BetaGen 33 36.0 - 28.8 kW 120 V 240 Amps
- 38.0 30.4 kW 220 V 79 Amps
BetaGen 40 43.0 - 34.4 kW 120 V 286 Amps
- 46.0 36.8 kW 220 V 96 Amps
BetaGen 49 47.0 - 37.6 kW 120 V 313 Amps
- 50.0 40.0 kW 220 V 105 Amps

Generating Sets: 60Hz, 3000 rev/min

BetaGen Model Max. kVA Output24 Pole @ 3,000 rpm kW Volts
Maximum Load
1 Phase 3 Phase
BetaGen 4/2 4.0 - 4.0 kW 120 V 33 Amps
BetaGen 6/2 5.7 - 5.7 kW 120 V 47 Amps
- 8.4 6.7 kW 220 V 17 Amps
BetaGen 11/2 11.3 - 9.0 kW 120 V 75 Amps
- 12.5 10.0 kW 220 V 26 Amps
BetaGen 22/2 22.0 - 17.6 kW 120 V 146 Amps
- 24.0 19.2 kW 220 V 50 Amps
BetaGen 25/2 28.0 - 22.4 kW 120 V 186 Amps
- 30.0 24.0 kW 220 V 63 Amps

Generating Sets Downloads

If you have any questions please do not hesitate to contact us.

Beta Marine Generating Set Output - 50Hz Information.
Beta Marine Generating Set Output - 60Hz Information.