What Size Generator Do You Need?

Here are some tips intended to help you decide which is the right generator for you and /or your businesses.

Sizing guidelines differ slightly between engine driven generators and tractor driven generators.

The first sizing decision involves making sure you have the proper kind of generator for your particular standby needs. If your needs are critical for animal survival or large-scale refrigeration, you will probably be better off with an engine driven system with an automatic start feature. This is especially true if operators can not be present at all times on the property.

If your needs for power are somewhat interruptable, you have blackout alarms and operators are present, you may prefer a tractor driven system. With a tractor driven system you also have a more portable power source. In some cases you may want one or more stationary engine driven units as well as one or more portable tractor driven units.

You must also calculate in the extra wattage needs for the starting of electrical motors. These motors require three to ten times its normal running watts to start them. Code G motors are the easiest to start. Starting amps for G type motors are usually three times motor nameplate amps. Examples of G type motors are furnace or fan blower motors, refrigerators and freezers, and above ground jet type water pumps.

Code L, M and N motors are extremely hard to start, starting amps for these motors are usually six to ten times the nameplate amp rating. Typical examples of L, M and N motors are air conditioners, air compressors and submersible underground water pumps. If you only have volts and amps multiply the two together to get watts. (1000 watts = 1 kW)

Use the actual wattage listed on the manufacturer nameplate whenever possible in order to ensure proper sizing. See typical running wattage requirements below for preliminary estimates.

HOUSEHOLD REQUIREMENTS	WATTS	FARM EQUIPMENT	WATTS
Air Conditioner	575 - 2,000	Bulk Milk Cooler 1 - 12 HP	1,000 - 10,500
Blender	200	Electric Fence	7 - 10
Bread Maker	600	Feed Conveyor 1/2 - 5 HP	575 - 4,500
CB Radio	50	Feed Grinding 1 - 10 HP	1,000 -9,000
Central Air	2,000 - 4,500	Gutter Cleaner 3 - 5 HP	3,000 - 4,500
Color TV	50 - 600	Infrared Lamp	250
Coffee Maker	850 - 1,200	Milking Machine 1/2 - 5 HP	575 - 4,500
Computer	400	Milk Parlor Heater	2,000 - 10,000
Deep Freezer	200 - 500	Shop Tools 1/6 - 1 HP	215 - 1,000
Dishwasher	400	Silo Unloader 2 -71/2	2,000 - 7,000
Electric Fry Pan	1,150	Space Heater	1,000 - 5,000
Electric Grill	1,250	Ventilation Fans	215 - 1,000
Electric Oven	4,000 - 10,000	Water Pump 1/3 - 2	400 - 2,000
Elec. Range Burner	1,000 - 1,200	Yard Light	100 - 1,000
Furnace Fan	1,200
Hair Dryer	1,500
Hot Plate	1,200
Hot Tub	1,700
Hot Tub Pump	750
Iron	1,000
Light Bulb	40-100
Microwave Oven	800 - 1,200
Radio	10 - 200
Refrigerator/Freezer	200 - 600
Toaster	1,150
Toaster Oven	1,200
Vacuum Cleaner	600
Water Heater	1,500 - 4,500
Waffle Iron	1,100
Window Fan	250

Guidelines For Tractor Driven Generators

1. Make an inventory of all property objects that use electricity. Determine the running wattage for each object. Although charts are available to help make such calculations, it is safer to look at the specific required wattage on the nameplate of each object.

2. For items with motors, determine both the running wattage need and the starting wattage need. Appliances and tools with induction motors may require 3 to 10 times the running wattage when starting. If a starting wattage requirement is listed on the motor nameplate use that figure instead of a typical estimate.

3. Determine which electric loads can be interrupted for extended periods and which are critical uninterruptable loads. This will help determine whether a smaller capacity, portable tractor generator can be shared among loads that can be delayed or sequenced.

4. Determine which interruptable loads may be kept unused all or most of the time in a standby power situation to minimize unnecessary power demands.

5. Sum the wattage of all essential electric heating and lighting loads to determine the base wattage value.

6. If you can stagger the starting of electrically operated motors, add to the base wattage, the starting watts of the largest motor and obtain a total.

7. Add base wattage and the running wattage of the largest motor to the starting wattage of the next largest motor and obtain a total.

8. Add base wattage and the running wattage of the two largest motors to the starting wattage of the next largest motor and obtain a total.

9. Continue calculating until all loads to be operated at the same time have been considered. You will need a generator with a starting capacity at least equal to the maximum wattage required in the calculations. The total motor and appliance starting watts should not exceed 150% of the generator continuous output rating - not overload capacity.

10. Generators can last considerably longer if they are not used at full capacity 24 hours a day. We suggest that you buy 10% to 20% more kWs than you think you need if you want to maximize your generator longevity. If possible turn off your generator at least 2 hours a day to further increase the lifetime of your system. All makes of generators benefit from such treatment.

The best way to contact us is via our secure online contact form. We are able to respond to online info requests far more quickly and accurately than any other method of contact, usually within 24 hours.

Currently we are supplying only gensets with a rating of 500 Kvw and greater.

Unfortunately, due to time constraints, we cannot respond to information requests for smaller power systems.