Sizing Emergency Power Generators

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The right "size" emergency power generators provide just enough wattage to operate all your essential equipment. Too few watts and you can overwork the generator, potentially damaging it and anything plugged into it. Too many and you'll waste money on the initial purchase and on the fuel to run it.

Assessing your residential or commercial needs

The most reliable way to assess the size of an emergency generator you need is to use an ammeter, a device that measures electrical current. With an ammeter, a qualified electrician can determine exactly how much power your business needs. Some electrical generator dealers will visit your location and do this as part of the sales process.

Be aware that any electronic appliance with significant moving parts - fans, pumps, compressors on refrigerators or air conditioners - can require up to three times as much power to start up than it does to run continuously. Make sure this start up power requirement is factored in to your measurements.

Don't guess. Rules-of-thumb based on the size of your home or business never provide a good substitute for actual investigation of the devices your emergency generators will work with.

With your situation and power requirements in mind, here's a quick rundown on some of the most popular residential, commercial, and portable emergency generators.

Emergency generator options include:
Kohler Generac Briggs and Stratton Generac Honda Honeywell
Output 14 kW 14 kW 48 kW 100 kW 3,000 watt 7,500 watt
Fuel LP, Natural Gas LP,Gasoline, Natural Gas LP, Natural Gas Natural Gas Gasoline Gasoline
Intended Use Residential Residential Commercial Commercial Portable Portable
Coolant Air Air Liquid Liquid Air Air
Average Cost $3,700 $3,000 $14,000 $24,000 $2,000 $1,000

What size emergency power generator to buy

Once you've factored in your start up requirements, you'll have an idea how many watts you need from your emergency power generators. To avoid overworking your generator, you should plan on purchasing one with a rated capacity of around 20% more than your exact requirements. This will give you room to add a few small devices, in addition to helping extend the lifespan of the power generator.

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