How to Select an Inverter for Your Needs

Home-Sized Inverters

The largest share of inverters being sold on the worldwide market today are for use in home energy systems. In the early days of the industry, inverters were built for remote, off-grid use where commercial power was unavailable. However, today most inverters in developed countries are being used for on-grid applications where utility feed-ins or interties allow for clean, renewable energy to be produced and distributed into the larger public utility systems, displacing some of the energy previously supplied by burning coal and oil, or nuclear reactors.

Off-grid and on-grid inverters serve two entirely different types of needs. On-grid inverters are subdivided into two further categories -- with and without battery backup. The type of inverter you will need is based on whether or not utility service is available at your location, and if available, how reliable that service is compared to your needs.

Off Grid

As primitive as the earliest inverters were, they provided the ultimate luxury and modern conveniences for living in wilderness locations far from civilization. While this market still exists to a limited extent in the United States, off-grid systems are more prevalent in countries with a less developed nationwide utility infrastructure. No matter where you are, if your property is off-grid, it's likely that bringing in the utility even a short distance will cost a great deal more than setting up your own off-grid electrical system.

Off-grid inverters are much more sophisticated these days, with capabilities of coordinating battery maintenance and charging regimens, and turning on backup power automatically, making these systems easier to maintain, simple to use, and worry free. As with portable systems, while less expensive inverters are available for off-grid homes, the difference in price hardly compensates for putting up with the inconvenience and inadequacies, except for the most primitive of cabin or remote application systems.

Choosing the right inverter for your off-grid system is based on accurately calculating your electrical loads and usage patterns. This assessment needs to be done carefully and with absolute honesty to yourself so that your entire system is sized correctly and will function without failure. The size inverter you need is based on what is called your "peak load" requirements -- all the AC loads that could be turned on at the same time.

You may find that you need to approach your load calculation exercise more than once in your planning phases because reducing your loads will yield very big savings in how large your system needs to be and how many hours your backup generator may need to run. The standard axiom in the industry is that every dollar spent on efficiency will yield $3 to $5 in system cost savings.

Inverter efficiency is another factor to monitor carefully for a home energy system. Inverters are generally most efficient when operated at or near their peak output, for example, a 1,500-watt inverter powering close to a 1,500-watt load. Most of the time, however, your inverter will be running a wide range of loads, usually not at its peak capacity. So, choose an inverter that has high efficiency over a broader range of loads. Other considerations are to match the inverter to the system's input voltage (often 12,24, or 48 volts), and an output voltage that matches the loads, i.e., 120 or 240 volts. Collect manufacturer's specification sheets and study them carefully, and ask for advice from the pros about any questions you may have.