>How to Select an Inverter for Your Needs
For portable power needs, smaller inverters, ranging in size from 100 to 2,000 watts or more are available for either marine, RV, or other smaller off-grid applications, such as a tool shed or barn. These portable inverters are meant for locations without utility electricity, and are used to convert DC electricity from a battery that is either charged by your vehicle's motor, or a standalone generating source like a photovoltaic (PV; solar-electric) panel, wind generator, or engine-generator. Marine inverters are built to withstand harsh weather conditions and corrosion from exposure to salt water, so if you're planning to use your inverter on a boat, choose a seaworthy type.
Depending on the types of appliances you will be running and how sensitive they are, you can choose between pure sine wave inverters or what are called square-wave or modified square-wave inverters. Modified square-wave inverters cost less than pure sine-wave inverters because they perform less sophisticated power conversions, delivering choppier transitions in the alternating current's output. When running appliances that have motors (such as refrigerators, drills, fans, etc.), modified square-wave inverters will run these motors hotter and consume 30% more energy than if you used a pure sine-wave inverter. It's a bit like running a car on square wheels instead of round ones. The car will go forward, but it will run far less efficiently and the ride will be darn bumpy.
For some appliances and electronics, such as motors, televisions and computers, and battery chargers for cordless tools, a poor waveform can cause overheating, damage the equipment, or even cause complete malfunction. Other potential problems are inverter noise in devices like compact fluorescent bulbs, radios, stereos, and televisions. For most people, the small difference in price makes it worthwhile to buy a pure sine-wave inverter in the first place so that they don't face limitations later if they want to use their inverter for another appliance.
The size of your portable inverter depends on what appliances or tools you are planning to use and their power requirements, called the "load." You will need to know how many continuous watts your tools require to run, how many different tools you plan to run at the same time, and also how much of a surge, or power draw, they have when first starting up, as with some larger motors like power saws.
This information for each tool is usually found on what is called a "nameplate." The nameplate rating will give the information either in watts or in volts and amps. For general purposes, multiplying the volts times the amps gives you the number of watts (V x A = W). For determining power surge requirements, see the tool manufacturer's specifications, measure with an ammeter, or "guesstimate" it by multiplying the continuous watts times three (although the surge can sometimes be as much as seven times).
