A solar inverter converts electricity generated by your solar panels (this is direct current, or DC, power) into power that can be used in your home for your computer, television and other wired products (this is alternating current, or AC, power). A solar panel cannot create AC power on its own; it needs help in the form of an inverter.
How AC power differs from DC power
In AC power, the current moves both forward and backward along a wire. In DC power, the current flows in just one direction. There are some products, such as light bulbs, that can run on either AC or DC power. However, electricity networks in the U.S. were built to use AC because that form of power can easily travel over long distances.
Devices that use DC power
It is true that televisions, phones and computers use DC power, and have to convert AC power back to DC power. That is what is going on in the small black box attached to the power cord of your laptop. However since the U.S. grid is designed for AC power, the products we buy are obviously also designed to use AC power. When a solar panel creates DC power, the inverter converts it to AC power so that it is compatible with the gird. That power is then inverted back to DC by the power supply on your electronic devices. Many countries use DC networks, but because we are in the U.S. we have to have inverters.
The efficiency of DC to AC (and back again) conversion
Usually, inverters have about 95 percent efficiency, meaning the conversion of DC to AC results in only about a 5 percent loss of power. Converting from AC to DC, however, is less efficient and results in anywhere from a 10-40 percent power loss. This is the case whether you are getting your power from the grid or your solar power system. If the black box on your laptop power card is hot to the touch, that means the conversion from AC to DC is low in efficiency.
The different kinds of inverters
The typical home has a central inverter, a box that converts DC power to AC. Many homes have that box on a garage wall. There are newer kinds of inverter, called a “micro inverters,” that work independently from each other and are located under each solar panel. These inverters take longer to install and are more expensive.
If you have any questions in regard to power inverters or any other components of a solar power system, please call POCO Solar at (408) 970-0680.