Generators Buyer's Guide

So, you are looking for dependable power for your remote cabin, your worksite, or for backup during a power outage. Head straight for the Generator Buyer's Guide to learn about common uses, how much power you will need and other information to match you up with the best generator for your needs.

Portable Generators for Emergency Power

The most economical way to supply power during a power outage is to use a portable generator of the appropriate wattage for your needs (at least 4000 Watts for starters) and run extension cords into the house to power chosen appliances. A safer system is to have an electrician install a power transfer switch, connected to the house's main electrical panel. Just fire up the generator, run a single extension cord into the transfer switch and power the circuits you need through the main circuit breaker. This eliminates the risk of electrical “back feed” injuring utility workers repairing downed power lines.

A small portable gasoline-powered electric generator can provide power for TVs, small kitchen appliances, hair dryers, power tools, lights and other comforts of civilization when you are out roughing it in the woods.

Portable generators can be put to work on construction sites that have no electrical service, providing clean, reliable power to operate saws, drills, air tools, air compressors, heaters, paint sprayers and other AC-powered tools. Most are gasoline-powered, a few run on diesel, and some models have multi-fuel capabilities, running on gasoline, propane or natural gas. These are generally full-featured machines with engine idle control, GFCI receptacles and 120 Volt full power switch.

Residential Standby Systems

An emergency home standby generator system can automatically restore power to your house in about 20 seconds. When the power goes out, the generator automatically starts and continues to run until power is restored. You can choose a generator that delivers enough power for the entire house (including air conditioning) or go with a smaller unit and power a few selected circuits, like the refrigerator, sump pump, furnace fan and several lights for basic survival.

These all-weather generators are installed outside the home and are wired through an automatic transfer switch (sold separately) to the main electrical panel. The use of an automatic transfer switch is required when generators are connected to home wiring.

Home standby systems can be fueled by natural gas, LP gas or diesel fuel. Many models can be connected to the home's natural gas line, eliminating the need to fill fuel tanks. Standby system capacities range from 6,000 Watts up to 40,000 Watts and more, and start automatically-even if you are not home.

Generators

Commercial Standby Systems

If you have a business that simply can't be without power or you have no existing source of electrical power for your home or business, you will need an industrial generator. These are typically stationary, heavy-duty units that generate single (120 Volt) or three-phase (120, 240 or 480 Volt) power. These massive systems are powered by water-cooled diesel engines, with some models generating up to 200 KW (200,000 Watts) of power. With the use of an automatic transfer switch, these generators can serve as backup power for large commercial or industrial operations, such as nursing homes, refrigeration operations, farms, large buildings and other businesses that can't go without power due to an outage.

RV Generators

Quiet, powerful gasoline, diesel or LP-powered generators can be installed in your RV, 5th wheel trailer, truck camper, tent trailer or travel trailer to provide electrical power.

PTO and Belt-Drive Generators

Create power on demand by attaching a generator to the PTO on your tractor or construction equipment. Belt-driven generator heads work with your existing gas engines. They are less expensive because the engine is not included.

Questions You Should Ask Before You Buy a Generator

  • What is the generator's wattage capacity and will it support your needs, including startup surge power required by some equipment?
  • Does the generator have enough outlets to plug in all of the items you want to power?
  • How noisy is the generator? Are there noise restrictions in your neighborhood?
  • What type of fuel does it use?
  • How large is the fuel tank and how many hours of operation will it provide?
  • Is the generator easy to move around? Does it have built-in wheels and handles for portability?
  • What accessories will I need to run the generator (fuel, heavy-duty extension cords, transfer switch)?

How Many Watts Will Your Generator Need to Produce?

Add up the wattage of tools, appliances and motors you want to run at the same time. Then select a generator with the RUNNING wattage rating to match or exceed the total load. Keep in mind that tools and appliances with electric motors require additional tool/appliance SURGE wattage at startup that can be double or triple the normal running wattage requirement. Look at the surge watts required and make sure you choose a generator with enough additional wattage to start them. Keep in mind that you typically are not starting more than half of the items at the same time.

Most home appliances and power tools are 120 Volts; larger appliances like electric stoves and clothes dryers may be 240 Volts. Generator power is measured in Watts: Amps x Volts = Watts

You can use our Wattage Chart to estimate the wattages of the tools, appliances and motors you will be operating at the same time. Wattage noted below are approximates only; please refer to tool or appliance itself for specific wattage required or order our easy-to-use tester below.

Reliance Amwatt Appliance Load Tester

Simple Plug-in Tester Gives Quick, Accurate Digital Readouts of Watt or Amp Usage
Use for refrigerators, dehumidifiers, space heaters, microwaves, holiday lighting, coffeemakers, hair dryers and more. Essential for calculating power needs for home transfer switches and emergency generator needs. More Info

Wattage Chart

Category Appliance Running Wattage Required Surge Wattage Required at Startup
Household/RV Coffee Maker 1750 0
  Dishwasher: Cool/Dry 700 1400
  Electric Fry Pan 1300 0
  Electric Range: 8in. Element 2100 0
  625W Microwave 625 800
  Refrigerator or Freezer 700 2200
  Automatic Washer 1150 2300
  Electric Clothes Dryer 1800 5750
  Furnace Fan (Gas or fuel oil): 1/8 HP 300 500
  Furnace Fan (Gas or fuel oil): 1/6 HP 500 750
  Furnace Fan (Gas or fuel oil): 1/4 HP 600 1000
  Furnace Fan (Gas or fuel oil): 1/3 HP 700 1400
  Furnace Fan (Gas or fuel oil): 1/2 HP 875 2350
  Lights As indicated on bulb 0
  Radio 50-200 0
  Sump Pump: 1/3 HP 800 1300
  Sump Pump: 1/2 HP 1050 2150
  Color Television 300 0
  RV Air Conditioner: 13,500 BTU 1500 2200
  Room Air Conditioner: 10,000 BTU 1500 2200
  Central Air Conditioner (for 2200 sq. ft. home*) 10,000 11,250
  Small Appliance 200 1700
Contractor 8in. Bench Grinder 1400 2500
  Pressure Washer: 1 HP 1200 3600
  7-1/4in. Circular Saw 1400 2300
  Electric Chain Saw: 14in. Bar, 2 HP 1100 0
  10in. Table Saw 1800 4500
  Drill: 3/8in., 4 Amps 440 600
  Drill: 1/2in., 5.4 Amps 600 900
Industrial Motors Split Phase: 1/4 HP 600 1000
  Split Phase: 1/2 HP 875 2300
  Capacitor Start Induction Run: 1/3 HP 720 1300
  Capacitor Start Induction Run: 1 HP 1600 4500
  Capacitor Start Capacitor Run: 1 1/2 HP 2000 6100
  Fan Duty: 1/6 HP 550 850
Farm Equipment Electric Fence: 25 Miles 2500 0
  Milk Cooler 1100 1800
  Milker (Vacuum Pump): 2 HP 1000 2300
  Portable Heater (Kerosene, Diesel Fuel): 50,000 BTU 400 600
  Portable Heater (Kerosene, Diesel Fuel): 90,000 BTU 500 725
  Portable Heater (Kerosene, Diesel Fuel): 150,000 BTU 625 1000
  Battery Charger: 15 Amp 380 0
  Battery Charger: 60 Amp with 250 Amp Boost 1500/5750 0
  Battery Charger: 100 Amp with 300 Amp Boost 2400/7800 0
  Electric Welder: 200 Amp AC 9000 0
  Electric Welder: 230 Amp AC at 100 Amp 7800 0
Computers Desktop 600-800 0
  Laptop 200-250 0
  Monitor 200-250 0
  Fax 600-800 0
  Printer 400-600 0

*Based on average-sized unit. Central air conditioners differ in wattage requirements; consult owner's manual for specific wattage requirements.

Finally, add together the wattage requirements for all the electrical devices that you want to run, to determine the minimum continuous wattage, or start at the same time, to determine the minimum surge wattage, you will need from a generator.

Minimum Recommendations for Typical Home Standby Power (1 kw = 1,000 watts)

Typical Home Standby Power Needs

Customer Type Appliance One Item at a time Two Items at a time All Items at once
Customer #1 Lights 2.4kw 4.5kw 6.6kw
  Color Television 2.4kw    
  Furnace Fan 2.4kw    
  Freezer 2.4kw    
  Refrigerator 2.4kw    
  Sump Pump 4.5kw    
Customer #2 Includes Customer #1 and central air 4.5kw 6.6kw 10.5kw
Customer #3 Includes Customer #1 and a well pump 4.5kw 6.6kw 10.5kw
Customer #4 All of the above 4.5kw 6.6kw 13.5kw

When in doubt, remember that bigger is better!

Safety Tips for Using Generators

Plug appliances directly into generator

Do not attempt to connect the generator directly to your home's circuits or wiring. Have an electrician install a transfer switch and plug the generator into this switch. This will keep the generator from feeding power back into the lines, which could put power company crews working on the lines at risk. This will also protect your generator and home wiring from damage when power is restored.

Use heavy-duty extension cords from the generator, as overloaded cords can cause fires and equipment damage. Make sure cords are placed to avoid tripping hazards, but don't put underneath carpets where heat may build up.

Never run a generator indoors and make sure there is proper ventilation around unit.

Never add fuel while generator is running. Avoid spilling fuel on hot components and put out all flames or cigarettes when handling fuel.

Consider tri-fuel generators to avoid multiple trips to the gas station and downtime.

Always have a fully charged, approved fire extinguisher near generator.

Don't overload the generator. Use only when necessary to power essential equipment.

Be cautious handling electrical cords in wet conditions.

Generator Engines and Alternators: What to Look For

Brand Name
Choose a portable generator equipped with a brand-name engine that you know and trust, such as Honda, Briggs & Stratton, Tecumseh, Yamaha and McCulloch.
OHV (Overhead Valve) Engine
OHV engines start easier, run quieter, last longer and produce less emissions than side-valve (pushrod) engines.
Cast Iron Sleeve
The cast iron sleeve is a liner in the cylinder of some engines which reduces wear and makes the engine last longer. The added cost of an engine with a cast iron sleeve is small and well worth it, if you expect to operate your generator often or for long periods of time.
Low Oil Shutdown
This feature shuts the engine down if the oil level drops below a safe operating level, especially recommended for generators with large fuel tanks.
Electric Start
Enables easy starting of generator without having to pull a starter rope.
Full Power Switch
Allows you to switch off the 240 Volt output to get more 120 Volt power from the generator, useful for starting 120 Volt electric motors on air compressors and water pumps.
Idle Control
Automatically throttles down engine when no power is being drawn from alternator, reducing engine wear and noise.
Hour Meter
Keeps a record of how long engine has run. Can help with oil change scheduling.
Portability Kit
Includes wheels and handles for moving the generator around. Can be a real back saver when using units that weigh over 100 lbs.
Large Fuel Tank
Generators with a fuel tank of 5 gallons or larger can typically run 7 to 10 hours on a single fill, useful for providing backup power during power failures.
All-Metal Alternator
Get an all-metal alternator because plastic housings can warp over time and cause the moving parts of the alternator to come out of alignment and break or wear excessively.
Total Harmonic Distortion (THD)
Total Harmonic Distortion is a means to measure the quality of electricity. 6% THD is considered the upper limit for "clean" electricity. Above 6% THD the electricity may reduce the life of electrical circuits, cause microprocessors to malfunction and cause furnace controllers to operate incorrectly. All NorthStar generators have THD less than 6%. Some generators produce THD greater than 15%.
Brushless Alternator Design
Brushless alternators require less maintenance and produce cleaner power that is more suitable for sensitive electronic equipment. Brush-type generators have brushes that are wear items, requiring replacement.
Ball Bearing Alternator
Get an alternator that uses ball bearings instead of needle bearings. It will last longer.

Generator Fuel Types: What to Consider

Generators use either gasoline, diesel, natural gas or propane. Here are the advantages of each fuel type.

Gasoline
Most common fuel source and is easily obtained; has short shelf life
Increases portability of smaller generators
Propane
Long shelf life
Clean burning
Easily stored in both large tanks or smaller 5-10 gallon cylinders
Obtainable during power outages
Home delivery available for large tanks
Natural Gas
Unlimited fuel source, no refilling required
Clean burning
Available during power outages
Diesel
Least flammable fuel source
Easily obtained
Fuel delivery available

Generator Sound: Determine Volume

Sound Intensities: How loud will it be?

Sound intensities are typically measured in decibels (db). A one decibel change is the smallest volume change detectable by the human ear. The Decibel scale is logarithmic rather than a linear scale.

How Loud is It?

Decibels Degree Comparable Loudness or Feeling
140 Deafening Jet aircraft, Artillery fire
130 Deafening Threshold of pain, Causes immediate ear damage
120 Extremely Loud Thunder or Diesel engine room
110 Extremely Loud Close to a train
100 Very Loud Wood saw, Home lawn mower, car horn @ 16 ft.
Over 90 decibels - Hearing can be damaged if protective equipment is not worn
90 Very Loud Symphony, Truck without muffler
80 Loud Car noise @ high speed, Police whistle
70 Loud Normal street noise, Average radio
60 Moderate Normal conversation
50 Moderate Normal office noise
40 Faint Residential area without vehicle traffic
30 Faint Quiet conversation
20 Very Faint Whisper, Ticking of a watch
10 Totally Quiet Soundproof room, Threshold of hearing

Cordsets + Plugs

Check out our selection of Generator Cordsets + Plugs.

Installation/Initial Set-Up

Current Power
Maximum Extension Cord Length
Amps at 240V Load (watts) #10 Ga. Cord #12 Ga. Cord #14 Ga. Cord #16 Ga. Cord
10 2400 250 ft. 150 ft. 100 ft. 75 ft.
20 4800 125 ft. 75 ft. 50 ft. 25 ft.
30 7200 60 ft. 35 ft. 25 ft. 10 ft.
40 9600 30 ft. 15 ft. 10 ft. NA
50 12000 15 ft. NA NA NA

WARNING: Use of undersized extension cords can cause electric shock, fire, or damage to connected devices. All extension and appliance cords must be in good condition and not worn, bare, frayed or otherwise damaged.

WARNING: Use of damaged electric cords can cause electric shock or fire. Note: If an extension cord becomes hot to the touch, it is overloaded or damaged and must be replaced.

Northern Tool is NOT responsible for damage or injury resulting from customer use of inadequate extension cords

Still need help?
Email our product experts, or Call 1-800-221-0516 our 24-hour sales line.