The Ultimate Generator Buying Guide

How To Choose the Best Generator

Do you need a power generator but don’t know where to start? Look no further. Acme Tools has assembled the ultimate generator buying guide for you.

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Types of Generators

Portable Generators

A standard portable generator uses a combustion engine to create alternating current or AC. They are cheap and produce a practical amount of power. To get a feel for what’s available, check out our favorite portable generators from 2017.

• Many are either mounted on wheels for easy moving or have wheel kits available separately.
• Great as tailgating and camping generators.
• They can even be used as a home generator using a transfer switch.

Standby Generators

Standby generators provide backup power to your home or business when utility power goes out. They are wired directly into the electrical system using a transfer switch. They are stationary and cannot be moved once installed.

To learn more about home backup generators, read our article about Generac Standby Generators.

• It can be programmed to automatically turn on as soon as the electricity goes out.
• If you are worried about losing power while you’re not around, you need this.
• They can be hooked up to your natural gas supply.

Inverter Generators

Inverter generators produce direct current (DC) like a battery, then “invert” it back to alternating current (AC) that comes from an outlet. The result is known as clean power, suitable for delicate electronics.

To know more about why this matters, read our post about Clean Power.

• An ideal small portable generator because they are so easy to pick up and move.
• Sometimes called silent generators, they aren’t louder than a normal conversation.
• They have small tanks and are highly fuel efficient.
• It can run in parallel to get twice the power. This gives more watts than a single unit to keep small appliances running.

Industrial Generators

Industrial generators have many features similar to standard portable units and inverters but have additional safety components.

• Built on rugged frames to withstand harsh job site conditions.
• Feature lifting hooks for easy lifting with a crane
• Ground-fault circuit interrupters (GFCI outlets) for use in inclement weather.

Welder Generators

Welder generators are welding machines with an on-board generator to provide power anywhere. These are designed for when an external power source isn’t available, such as repairing a tractor.

• Provide enough extra power for lights and other metalworking tools
• Some are strong enough to run a home, farm, or small business if the power goes out.
• They are big and heavy and typically made for farm and ranch use.

Power Takeoff (PTO) Generators

PTO generators harness the rotation of a tractor engine to generate current. They are made almost exclusively for farm and ranch use.

• Because of the high horsepower of tractors, these generators are potent.
• They do not use any fuel and have deficient maintenance.

If you want to check the best of all types of generators, check out the Best Generators of 2017.

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Wattage & Power

Watt do you mean?

Imagine a 15-amp circular saw. It (theoretically) draws 15 amps of current while in use. That’s multiplied by 120 volts, so it needs 1,800 watts of power to run. The total watts of all tools or appliances you plan to use should be less than your generator’s rated wattage.

Take a look at the watt draws of some typical generator applications.

Rated vs. Surging Watts

Generator wattages have two different numbers: rated and surge. The rated wattage is how much power the generator can consistently sustain for extended use. Surge wattage is the maximum power it can make, but only for a very short period. Surge rating is sometimes called “maximum,” “spike,” or “peak.”

Never run a generator at peak wattage for more than 30 minutes, or you could damage the internal components. Rated power is generally about 90% of the maximum.

When do I need surge watts?

You need surge watts for most tools or components that need to build momentum, such as refrigerator compressors or fans. Also, anything encountering resistance, like a chainsaw cutting through a log. Starting these will pull more power than they would without that extra strain.

Many electronic devices that create heat or light, such as space heaters, draw a flat amount of power. If you are unsure how many watts your devices will be consuming, ask a licensed electrician, and they will help you get an accurate evaluation.

What wattage sizes are available?

Wattage	Example	Uses
1000		Camping, recreation, tailgating, powering small electronics. Very small and suitable for light use.
2000		Camping, recreation, tailgating, powering small electronics. Inverters can run in parallel for more power. More versatile than 1000 watts but still small and portable.
3000		Camping, RV camping, Home power. This Champion generator is made to power an RV and can burn gasoline or propane.
4000-8000		RV camping, emergency power, industrial uses. As outputs get bigger, it gets easier to use for backup power to a house or as an RV generator. This Honda 7000-watt inverter generator is quiet and can run a fifth-wheel trailer independently.
8,000-10,000		Jobsite, home backup, commercial.  Generators get very big and more complex to move, even on wheels. This Pulsar 10,000-watt duel fuel generator burns gasoline or propane and has two additional outlets that can deliver 240 volts.
10,000+		Emergency and PTO generators.  They range from as small as 8,000 watts all the way up to 40,000 and beyond.  You would need to contact an electrician to get an accurate estimate of what size fits your needs. Generac made a generator sizing calculator to give a rough idea of what you need.

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Generator Fuel Types

Gasoline-Powered Generators

Gasoline is the most common type of fuel for portable generators. It is easy to refill and works great in small engines. If you run out, running to a gas station makes it easy to get more. 

• Pros: Easy to refuel, portable, most extensive selection, lots of sizes available.
• Cons: Toxic fumes, exhaust, and gas have a limited shelf life and runtime.

Liquid-Propane-Powered Generators

Liquid propane (LP) is another common fuel used in portable generators. LP units hook up to propane cylinders just like a barbeque grill. If you run out, most gas stations keep a stock of prefilled tanks. They can also attach to large above-ground tanks with much longer running time than gas generators.

• Pros: Longer runtime than gas, clean burning, easy to get more fuel.
• Cons: Higher risk of leaks than gasoline, has trouble staying pressurized in cold weather, less energy than gas.

Natural Gas-Powered Generators

Natural Gas generators are powered by the gas already piped into a house, just like a stove. A professional should also only connect an NG generator to a gas line. Gas leaks are hazardous, and you do not want them to happen to you.

• Pros: Unlimited fuel, cheap, clean burning.
• Cons: The generator is immobile, there are possible gas leaks if set up improperly, and it is impractical in earthquake zones.

Diesel-Powered Generators

Diesel generators run on diesel fuel like semi trucks and train engines. Since the engines are large and heavy, you won’t find as many portable diesel generators. Some diesel units are so big that they’re mounted on forklift openings for transportation, such as this Kubota Lowboy generator.

• Pros: Extremely high energy output, minimal maintenance, durable construction, long lifespan, easy to refuel.
• Cons: Loud, high pollutant, big and heavy, not easy to move, high initial cost.

Dual-Fuel Generators

A dual-fuel generator can burn either gasoline or propane. This is an excellent option for a long-running time if you have an above-ground propane tank. A gas-powered generator that is great for camping and recreation. Propane gives it a long runtime for emergency home standby power.

Tri-Fuel Generators

A small selection of units can draw power from gas, LP, or natural gas. They are great for being both portable and practical as home backup generators. They have the advantages of all three fuels but are generally only available in higher power outputs. If you need versatility, this is the best generator for you.

Tri-fuel generators are the most flexible units in natural disasters. Natural gas lines might not always be open, especially if you live in an earthquake zone. When the power goes out, you can use gasoline or liquid propane until emergency crews arrive.

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Physical Sizes & Generator Portability

Small Generators

• Small units are great for camping, recreational use, and any other situation with adequate small-watt output.
• If you have trouble lifting heavy objects, opt for a more compact model.

Large Generators

• There is no substitute when lots of power is needed.  Best for RV camping, construction sites, or whole-home backup.
• Most manufacturers have wheel kits to make moving easier if the weight is too heavy.

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Generator Outlets

Let’s look at the three most common outlets on generators.

Wall Outlets

• Most generators come standard with at least 2 regular 120-volt wall outlets.
• The more powerful a unit is, the more outlets it may have.
• If you need to plug many things in, get a more significant generator.
• Be sure to get GFCI outlets if you might use them in damp conditions.

RV Outlets

• Larger generators have a 30-amp outlet to run an RV.
• The pictured outlet is circular and has a twist-lock, so the cord doesn’t accidentally pull out.
• An adaptor may be needed for some RVs. Check your model to be sure what shape the plug is.

120/240 Volt Outlets

• Large generators often boast an additional locking 120/240 volt outlet.
• Suitable for well pumps and other large appliances
• Generally only seen on units with at least 4000 watts

Other Outlets You Might Find

• 240-volt non-locking outlet
• Parallel adapter outlets.
• Battery charger outlet
• 12-volt adapter (car charger port)
• USB

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Generator Accessories

Various generator accessories can help you maximize the versatility and efficiency of your generator.

Transfer Switches

A generator transfer switch transfers the power source of your house from utility power to the unit. They are hardwired into your home and should only ever be installed by a licensed electrician.

• You need a transfer switch if you want to plug your generator into your home circuits.
• Connecting a generator without one can destroy your home’s circuitry and hurt utility workers repairing the lines outside.
• Transfer switches can either be automatic or manually operated.

Generator Parallel Kits

Parallel kits are great for camping and powering RVs. Honda even has a companion generator with 30-amp locking outlets that are explicitly made for campers.

• Allows you to connect two inverter generators together to get twice the wattage.
• Saves money by not having to invest in a more significant generator.
• When you don’t need the extra watts, simply go back to using a single generator and save gas.

Extension Cords

Only use a generator outside, at least 15 feet from the house, to avoid poisoning from carbon monoxide. As such, only outdoor-rated extension cords should ever be used to power your needed appliances. As more power is required for larger appliances, also be sure that the cord you are using is strong enough to carry the electrical load.

• An outdoor rating means the jacket will be thicker and more durable than most cords in your house. Some also have a built-in GFCI to protect you if it is damp.
• Even cords with lighted ends can be found more easily in the dark.
• Don’t get a cord longer than you need. Too much length will take away from the power delivered.
• If you need extra plugs, use a power splitter. Depending on your needs, splitters use either the standard or the locking outlets.

Fuel Extenders

• Safely adds to the runtime of the unit before it needs refueling.
• Some have two hoses that connect to two parallel inverter generators simultaneously.
• Most are made specifically for a particular model, so check specifications before buying one. To learn more, check out our B.E.R.G.S. Fuel Extender Buying Guide.

Generator Covers

• Some manufacturers make fitted covers for specific models.
• Non-fitted third-party covers without flashy brand logos can reduce the threat of theft but don’t offer the same protection.

Wheel Kits

• Not all generators come standard with wheels.
• Wheels make moving heavy generators easier, especially on rough ground.
• Check before buying to ensure the wheels are compatible with your model.

Cold-Weather Kits

• It keeps the battery and oil warm and ready to go in backup generators.
• Needed in cold climates to ensure standby power can turn on in the middle of winter.

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Other Important Generator Facts

Engine Serviceability & Manufacturers

Some brands use motors made by other well-known companies and build the rest of the surrounding components. Honda and Generac are two common engine names that you will encounter. These manufacturers’ engines are straightforward to fix and find parts for.

They also already have well-established networks of service centers, so getting repairs done is much easier. Remember, a generator is a long-term investment that will likely outlive the manufacturer’s warranty. Be safe and get one that will stay working for many years.

Low-Oil Shutoff Function

If the motor oil gets too low, this feature will automatically cut power to the engine to prevent damage. This saves you money on repairs later. You want this feature. 

Generator Lifting Point

For industrial users, a lifting eyelet can be very important. It provides a secure attachment point for a crane to safely lift the unit. Keeping the generator up on the crane also keeps it out of reach of hooligans at night.

Covered Outlets

Covers protect the outlets from rain and other foreign debris. They can prolong the lifespan of the entire system. If you plan to use a generator frequently or store it outside, ensure the outlets are sealed.

Standard generators need a pull cord to start. An electric start turns the motor on with just the turn of a key. Even on cold mornings, you won’t have any trouble getting the motor started. If you have a hard time with heavy pullcords, it would be worth the extra cost.

A few manufacturers have models with a remote starter, just like a car. Imagine turning on the heat in the middle of a heavy blizzard without ever stepping foot outside. 

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