This article gives a comprehensive overview for picking the right generator for your emergency needs, and for any budget. Nearly every disaster that can strike a home carries a risk of power loss. If a power grid is damaged enough, utility companies may take weeks to get power running again. While investing in a generator is a sound idea, many questions should be answered first to figure which appliances you will need to maintain power to. You could well overspend on a generator with capabilities you don’t need, or underspend on a generator that doesn’t have the juice to fulfill your expectations.

 Do you live in a warm weather climate? If so, your concerns will be chiefly to keep freezers and refrigerators running, and possibly to run fans, power-hungry air conditioners, and wet-dry vacuums, which go a long way towards cleaning up flooded rooms and minimizing the long term damage from mold infestations.

Do you live in a cold weather climate? Being snowed in certainly presents a very different existential quandary. In this case, refrigeration is not an issue if the air outside is freezing. Perishables that are adequately sealed fare well outside, if food preservation is an issue. The big issue in a cold weather emergency is hypothermia! Getting power to the furnace or to space heaters and making sure the best insulated room in hour house can stay warm until power is restored is going to be your chief concern.

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Determine Power Requirements
You will need to determine your power requirements first, bearing in mind the limits of a portable generator. The table below shows approximate voltage for different appliances. The nameplates or manuals of most electric devices will usually show their power requirements. The number you are concerned with, is watts. If watts aren’t displayed, just remember that watts = volts x amps. Otherwise, a trained electrician can measure the energy requirements of any given appliance with a device called an ammeter.

 

If a device has many moving parts, such as fans, gears and other components, they will have a much higher power requirement to start up. Once started, the power required is much lower, but this should be factored into your requirements. If you are careful to turn these more power hungry devices on, one at a time, you should avoid overtaxing a generator. Note that air conditioners are the most voracious appliances of all, especially in terms of startup requirement, but these numbers are in a steady decline as manufacturers try to design more energy efficient models, so it’s crucial to check the individual unit’s power requirements rather than relying on these ballpark figures:

Appliance or Tool	Running Wattage	Startup Wattage
Air conditioner 12,000 BTU	1900	7600
Air conditioner 24,000 BTU	2800	11200
Air conditioner 32,000 BTU	3500	14000
Air conditioner 40,000 BTU	5000	20000
AM /FM Radio	225	225
Battery charger, 12 volt	200	200
Circular saw	1500	1900
Coffee maker	600	600
Computer, desktop	800	800
Computer, laptop	250	250
Crock pot / slow cooker	250	250
Dishwasher	500	1000
Electric blanket	1000	1000
Electric clothes dryer	750	2100
Electric range	2000	2000
Fan, 1/4 HP	600	1200
Freezer	600	1200
Furnace fan	1100	2000
Garage door opener	600	1200
Gas clothes dryer	1200	1200
Hand drill	500	750
Home security system	100	100
Hot plate	1200	1200
Hot water heater	5000	5000
LCD Monitor	30	30
Light bulb, 100 Watt	100	100
Light bulb, 50 Watt	50	50
Microwave oven	1300	1300
Mini-fridge	500	2000
Refrigerator	1200	1950
Space heater	1500	1800
Sump pump 1/2 HP	1200	3600
Toaster oven	1500	1500
TV, 20" flat screen	120	120
TV, 46" flat screen	190	190
TV, tube	400	400
Washing machine	1000	7500
Water pump 1 HP	1920	5760
Water pump 2 HP	2500	7500

 

Once you have an idea of what your energy needs are, give yourself at least 20% of headroom. This lets you plug a few extra devices in, as well as making sure the generator isn’t overburdened and extends it’s operating lifetime.

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Pick a Generator Type

Depending on your budget, you’ll have to decide what type of generator you need. The most common type of generator is a portable generator. They vary in size from less than a kilowatt to seven kilowatts, and range from $300 to $3000. They are easily available from most chain hardware stores, and don’t require an electrician if a [transfer switch] isn’t needed. Most run on gasoline, and will require a considerable amount of fuel stored to run for any length of time.

A larger sub-class of portable generators can exceed 200 Kilowatts, but are designed to be towed by trucks and run on diesel fuel. Homeowners that need something more powerful are better served with a permanently installed standby generator, hardwired into a home’s electrical system. These start at seven kilowatts and go up to hundreds of kilowatts. They will require professional installation by an electrician and will require a transfer switch. Like portables, they can run on gasoline or diesel fuel, but many use propane or natural gas. They are also fully enclosed and are designed to run much quieter that portables.

A third type of generator, is not really a generator at all. They are battery-inverter systems, and rarely exceed two-kilowatt capacities. As they only store, and do not generate electricity, they are not useful for more than short interruption in power. They run $600 to $1200 for models, but should a homeowner really want to think out of the box, some manufacturers now offer battery-inverters with solar panels and wind turbines connected to them in the $4500 to $6000 price range.

 

Transfer Switch
A transfer switch, once installed by an electrician, enables the generator to connect directly to a home electrical system. Standby generators will usually require automatic transfer switches. These smart switches automatically start the generator when power fails, and then will stop the generator when power returns to normal. Certain appliances, such as a furnace fan, will require a transfer switch to run on generator power.

Of course, if the generator is not of sufficient power to run all the appliances currently plugged in or turned on during the outage, it will require a mad dash of unplugging to get it to start. This can be avoided by having an electrician install a dedicated electrical sub-panel, which only connects to essential equipment. This ensures that during a power outage, only specific devices will connect to the generator, and will not overburden it.

 

Fuel Requirements and Storage
Unless you decide to go with a green-friendly battery inverter, your generator is going to require fossil fuels to burn. If you are looking to run it for multiple days, that’s going to require storing a significant amount of fuel.

Natural gas /liquid propane generators rely on utilities gas mains for power. While this is very convenient, ruptured gas mains are often the result of disasters like hurricanes and earthquakes, and cannot be relied on to power your generator.

Gasoline power is usually the domain of smaller portables. If you intend to use a portable during the day to keep your freezer from thawing out, and use a few essential tools, your fuel needs can be met with a few 5 gallon cans of gas, which should last long enough until gas stations are back in business.

Long term, heavy-duty operation, as in the case of standby generators is best served by 1800 RPM diesel generators. Fuel usage will be considerably more. Generator Joe (generatorjoe.net), the largest generator supplier on the internet, maintains a diesel fuel consumption chart on their site. According to the chart, 24 hours of use at ¾ capacity for a 20-kilowatt generator consumes roughly 31 gallons of fuel. With these kinds of fuel requirements you will want at least one standard 55 gallon drum to store your fuel. These drums are the only containers exceeding a five gallon capacity approved by the Uniform Fire Code to hold fuel.

Stored fuel, degrades over time, so you will want to buy a fuel stabilizer such as Sta-Bil or Pri-G., available at any auto supply store. Read the directions carefully and add the stabilizer first to your tank, and fill the tank to 95% capacity before closing .the cap as tight as possible. This keeps water vapor and air out of the tank . Adding stabilizer to fuel that has already begun to deteriorate won’t be nearly as effective, as these products are meant to be used with fresh gasoline. Store the fuel away from sunlight, preferably in temperatures under 80 degrees Fahrenheit.

 

Generator Safety

As combustible engines, portable generators must always be placed on a flat surface, well away from the home, as they generate large amounts of toxic carbon monoxide. Do not put a generator in your garage or in an enclosed space!

Generator also should be protected from the elements by an awning or carport. If the generator is not connected to a [transfer switch], homeowners should only use outdoor rated, grounded (3 prong) extension cords to connect the unit, and only directly to the appliances in question. Never, ever connect a generator to a wall socket!

For more information about generator safety please read our guide on how to operate a generator safely.