Why You Need an Inverter

Independent electric energy systems are untethered from the electrical utility grid. They vary in size from tiny yard lights to remote homes, villages, parks, and medical and military facilities. They also include mobile, portable, and emergency backup systems. Their common bond is the storage battery, which absorbs and releases energy in the form of direct current (DC) electricity

In contrast, the utility grid supplies you with alternating current (AC) electricity. AC is the standard form of electricity for anything that "plugs in" to utility power. DC flows in a single direction. AC alternates its direction many times per second. AC is used for grid service because it is more practical for long distance transmission.

An inverter converts DC to AC, and also changes the voltage. In other words, it is a power adapter. It allows a battery-based system to run conventional appliances through conventional home wiring. There are ways to use DC directly, but for a modern lifestyle, you will need an inverter for the vast majority, if not all of your loads (loads are devices that use energy).

Incidentally, there is another type of inverter called grid-interactive. It is used to feed solar (or other renewable) energy into a grid-connected home and to feed excess energy back into the utility grid. If such a system does not use batteries for backup storage, it is not independent from the grid, and is not within the scope of this article.

Not a Simple Device
Outwardly, an inverter looks like a box with one or two switches on it, but inside there is a small universe of dynamic activity. A modern home inverter must cope with a wide range of loads, from a single night light to the big surge required to start a well pump or a power tool. The battery voltage of a solar or wind system can vary as much as 35 percent (with varying state of charge and activity).

Through all of this, the inverter must regulate the quality of its output within narrow constraints, with a minimum of power loss. This is no simple task. Additionally, some inverters provide battery backup charging, and can even feed excess power into the grid.

Define Your Needs
To choose an inverter, you should first define your needs. Then you need to learn about the inverters that are available. Inverter manufacturers print everything you need to know on their specification sheets (commonly called "spec sheets"). Here is a list of the factors that you should consider.