How to choose an inverter size for home
Power inverters come in many sizes, measured in watts (W). 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 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. For example, if you have a two-outlet inverter and will be plugging in 2 devices at once, add up the total wattage of both devices, then add at least 50% more to account for peaks or spikes in the power draw. For example if your DVD player draws 100W and your laptop another 100W, a minimum 300W inverter ((100W + 100W) x 150% = 300W) is recommended.
Make sure the power of the inverter is listed as "continuous". Some inverters are listed at a certain wattage, but can only draw that wattage for a short period of time (i.e.: 5 minutes) and then will shut off, reset themselves and resume functioning. These outages can be frustrating to you and harmful to the device you are powering.
If the item is motor driven, it requires additional start-up (surge) wattage (typically 2-3 times the continuous wattage required) to start the device. For example, a saw that runs at 700W might require 1400W to start up. If your inverter only supplies 1000W, you will not be able to start it up. In this case, you would want to select an inverter rated at least 1400W surge to handle start-up needs.
