Volts (120) x Amps = Watts. To determine if several appliances can be operated at the same time, simply add up their wattage ratings to see if the total falls within the specifications of the power inverter.
This is known as peak or surge, and this information should also be listed on the device's label. Most inverters also have a peak rating, so make sure the inverter's peak rating is higher than the peak wattage of the device you intend to power. Microwaves are a special case. As an example, you may know that your microwave is a 500-watt microwave. This is actually the cooking wattage. Watts, Peaks and Surges. The first step in selecting an inverter is to match the inverter to the voltage of the battery you'll be using for power. In the majority of cases, you'll be using a 12-volt battery, so you would want to select a 12-volt inverter. The next step is to determine which devices you plan to power with the inverter. Look for a label somewhere on each device that tells you the wattage it requires to operat All inverters are rated in watts and most electrical appliances have a wattage rating. Use our online Calculator Tool to ensure the wattage rating of the largest load is within the wattage rating of the inverter you select. Pure sine wave inverters can run any of the modified sine wave inverter loads, as long as they meet the same operating and surge requirements of the load 4. Check your inverter or circuit. If the watt value of the circuit/inverter is less or equal to the number of watts your device uses, you should not use it. Also, when a device starts, especially one with a starting capacitor like a motor, it may draw more power than it is rated at. Use the numbers you found to calculate the device's wattage. Take the formula Watts = Amps x Volts and plug the numbers you found for the Volts and the Amps into their appropriate spots. 1  For example if the Amps = 12.52 and the Volts = 20, then the wattage of the device would equal 250.40 (that is 250.40 = 12.52 x 20). DC to AC power converters, or Inverters, are used to provide standard 120-volt AC power from a 12-volt DC source, such as a car or truck. Inverters allow you to power AC equipment that requires 120-volts and are rated in watts. This rating describes the maximum wattage that the inverter can provide.  To select an inverter from DonRowe.com that has enough power for your application, add the watts for items you may want to run at the same time. Use the total wattage, plus 20%, as your minimum power requirement. Note: The wattage's given below are estimates. The start-up load of the appliance or tool determines whether an inverter has the capability to power it. Be sure to check the specific wattage requirements and operating instructions for appliances / tools to be used. Also, air conditioners are a very difficult load because of the high start-up surge. At any rate to determine the amount of power required for a device it is best to base it off of the peak amount. Add the peak wattage, or amperage if you prefer, of each device together and the total is the amount of required power your inverter must generate to allow for the usage of these devices.  Choosing the Right Inverter Size. Power inverters come in many sizes, measured in watts. The amount of wattage you will require depends on the total draw of the devices you’d like to use. Many appliances and power tools have their wattage rating indicated on the product itself. Wattage rating can also be calculated by using this formula: Volts (120) x Amps = Watts. To determine if several appliances can be operated at the same time, simply add up their wattage ratings to see if the total falls within the specifications of the power inverter. A power inverter changes DC power from a battery into conventional AC power that you can use to operate all kinds of devices ... electric lights, kitchen appliances, microwaves, power tools, TVs, radios, computers, to name just a few. You just connect the inverter to a battery, and plug your AC devices into the inverter ... and you've got portable power ... whenever and wherever you need it. The inverter draws its power from a 12 Volt battery (preferably deep-cycle), or several batteries wired in parallel.
http://electronics.howstuffworks.com/gadgets/automotive/dc-ac-power-inverter3.htm http://gpelectric.com/company/how-determine-what-size-inverter-use http://www.wikihow.com/Calculate-Wattage http://support.radioshack.com/support_tutorials/batteries/pwrgde-8.htm http://www.donrowe.com/usage-chart-a/259.htm http://www.powerinverters.org/pages/Inverter-FAQs.html http://learn.compactappliance.com/power-inverters-guide/ http://www.donrowe.com/power-inverter-faq-a/258.htm
how is wattage determined on power inverter