This is a bad hurricane season. You want to be ready so you ask yourself, “What size portable generator do I need?”
A storm like Harvey doesn’t happen very often, thank goodness. Here at the Generator Grader, our hearts go out to all those affected by this storm of the century.
When a storm threatens, we consider our options in a power outage. Will we be lucky again? Or unlucky again? Truth is, it’s better to be safe than sorry. A portable generator is a good investment even when the weather is nice. If you’re visiting this site for a possible emergency, or if you already own a portable generator, just remember, “Always be safe!”
To save you some time, many new generator purchasers are only interested in one that can handle their refrigerator/freezer in a power outage. If that is you, look at one that provides at least 2000 surge watts. Although most refrigerators require less than 1000 watts to run, when the compressor cycles on, they need the additional watts.
You’ve made a decision to get a portable generator. Great! A common question that I get from shoppers looking for a portable generator is, “What size portable generator do I need for home use?” The best answer to this question is not very popular. The answer is, “It depends”.
Many people go make their portable generator purchase and wish that they had considered all the factors first. Let’s face it, generators are expensive and you don’t want to waste one while you purchase the one you should have bought in the first place.
Take for example two best selling generators. The Earthquake ig800w is an 800 watt inverter generator that can only power one or two items at a time. The equally popular Generac xg8000e is an 8000 watt generator that has enough power to hook up to your home’s power panel to supply most of your needs in a power outage.
Why one group of people think that one size is what they need and another group of people think a completely different size is what they need is why “it depends”.
For a better explanation of “it depends”, read below and take a look at the handy table which provides the estimated requirements of some standard household devices and appliances.
Running Watts vs. Surge Watts – What’s the Difference?
The two columns on the table that you need to understand are the “running” watts and “starting” or “surge” watts. The difference is that all devices require a certain number of watts to run continuously AND some require an additional number of watts to start or to cycle on. This is why portable generators are rated for their running watts and their surge watts. Running watts are generally 90% of surge watts on most portable generators. A generator should not be expected to run continuously above their rated running watts.
device running watts starting (surge) watts
Electrical Water Heater (40 gal.) 4000 0
Hot Plate 2500 0
Electric Stove - each element 1500-2500 0
Window Air Conditioner - 12000 BTU 1200 1800
Microwave - varies 625 800
Well Water Pump 1000 1000
Sump Pump 800 1200
Refrigerator Freezer 800 1200
Deep Freezer 500 500
Furnace Blower 800 1300
Computer 800 0
Television 500 0
Stereo 400 0
DVD Player 100 0
Box Fan 300 600
Clock Radio 300 0
Light Bulb 75 0
Radial Arm Saw 2000 2000
Circular Saw 1500 1500
Miter Saw 1200 1200
Reciprocating Saw 960 1040
Electric Drill 600 900
Air Compressor (1 HP) 1500 3000
Garage Door Opener 480 600
Security System 180 0
Resistive type devices do not require surge watts. These are generally heat producing devices such as light bulbs, toasters and coffee makers. Devices and appliances with an electric motor in them require an additional requirement of watts to “start” them. Starting can be as simple as flipping a switch as in a hair dryer or power drill. “Starting” in a refrigerator is quite different and will start and stop repeatedly. Listen closely to your refrigerator and you will hear it cycle on periodically as its fan, compressor or defrost cycle starts. These “surge” watts can be sometimes be two or three time the watts necessary to simply run the device.
What Size Portable Generator Do I Need?
When calculating the watts that you’ll need, you must consider this extra watt requirement. In reading this table, take a standard refrigerator/freezer for example. To continuously run the unit, you need approximately 800 watts. However when the compressor kicks in, it requires a the additional 1200 surge watts. So it takes 2000 watts to supply ongoing power to your refrigerator/freezer.
As it settles into its running watt requirement of 800, the difference of 1200 watts can then be used to power something else. If you have a low to mid watt generator (up to 3500 running watts) you may opt to run your refrigerator most of the time and and rely on it keeping itself cold with the doors closed, then unplug and switch the power to other needs.
Be aware when looking at other tables on other sites which explain estimated wattage requirements. Some include the running watts already added in the surge watt column.
So to give a better answer than, “It depends”, you need to ask yourself, “What do I need the portable generator for?”
- emergency use in power outage situations
- to hook into your home’s power as a standby
- for now and then use around the house
- for use on the job in remote locations away from electrical outlets
- for camping, tailgating, RV use
- all of the above?
Here’s a good rule of thumb, add up the running watts for the MOST devices that you’ll need at any given time. Then add in the highest surge watt requirement for any of those devices.
You then have the minimum watt requirement for the generator you’ll need. With well timed use of devices that don’t need to be used constantly, this should be enough power for you. If not, remember that you will have to unplug one or another to have enough wattage available. But here’s some wise words, no one ever said, “I wish I had LESS power.”
Let’s say for example that you have a power outage and you want to keep your refrigerator/freezer running continuously. According the the estimated watts on the table, you need 800 watts to power it, but will need periodic “surge” watts of 1200. Now if you’re running other devices off of the generator at the same time, for example a TV, stereo, and several lights, for an approximate total of 2000 running watts, and you are drawing at, or near the peak rated watts of your generator, when your refrigerator “surges” and you exceed the rated watts of your generator, you can trip the breaker and you’ll lose power output.
What Do I Need to Know about Watts and Amps?
Remember, this table is for convenience only and the figures are only estimates. Most appliances have their watt requirement (or Amps) usually printed somewhere on your device. The watts that you read on your device are not always the wattage that it will require. For example an 1100 watt hair dryer will produce 1100 watts of heat, but require more watts than that to power it. More accurately, if you know the Amp draw of your device, there is a handy formula that will let you calculate your watts:
Amps x = Watts
Volts is nearly always 120 in the US. If you know that your device requires 10 amps, then 10 amps x 120 volts = 1200 watts. Similarly you can calculate your Amps with the formula:
Amps = Watts/Volts
So you know your appliance is 1200 watts. Divide that by 120 (Volts) and that gives your your Amps equal to 10.
Sorry for the math lesson, but here at the GeneratorGrader we want to make sure that what you should know is available to you. See the article titled How a Portable Generator Works for a more detailed explanation of volts, watts and amps.
After you determine the size that will make you happy, you might want to consider other factors in determining the right portable generator for you. There are noise considerations. Whether you want to fuel with gas, propane, or diesel, or a combination of two or more fuels. Whether you require pure electrical energy for sensitive electronics. As you can see, when asking yourself, “What size portable generator do I need?”, you might want to arm yourself with more knowledge available in the other articles on this site.
In summary, ask yourself these pertinent questions before you decide on power alone. There is quite a difference between a 2000 watt All Power and a 2000 watt Yamaha inverter. More than just the $800 price difference! Once you know what size you want, know the advantages of an inverter type vs. a standard generator.
Filed under: What Size I Need