How to Size an Inverterby Anthony Smith
A power inverter is a device that will take DC, or direct current, electrical power and convert it into an AC, or alternating current power that is compatible with nearly all devices that "plug in" to get their power. These are very valuable to someone that is on the road with DC power available from their vehicle, but want to run AC devices. With quite a few different sizes of inverters available, it is important to know how to determine what size you will need before starting your shopping.
Make a list of all the AC powered items that you wish to be able to power with your inverter. For example, you may want to be able to power your laptop computer, a coffee maker, and your cell phone charger. Those traveling in an RV may have more items on their list.
Look at each device and find its power requirements in watts. This is usually found right on the device, on a label in the back, but occasionally you may need to refer to the owner's manual.
Total the power requirements in watts for all the devices. Also take a look at which devices you would normally be operating at the same time and take the total power requirements of just these devices.
Shop for an inverter while keeping these two numbers in mind. Purchase an inverter that meets one of these needs and also fits your budget. You may find that you can get by with using just a couple of devices at a time, and thus can buy a less expensive inverter with less capacity.