An inverter converts direct current (DC) electricity from solar panels and Batteries into alternating current (AC) electricity for household appliances. The inverter is a critical component of any solar power system, and its selection affects system efficiency, power quality, and compatibility with appliances. Inverters are rated in watts of continuous power output and surge capacity for starting motors.
String inverters connect multiple solar panels wired in series. They are the most economical for grid-tied systems with consistent sun exposure. String inverters have a single maximum power point tracker and operate most efficiently when all panels receive similar sunlight. Partial shading of even one panel in the string reduces the output of the entire string.
Microinverters attach to each individual solar panel, converting DC to AC at the panel level. Each panel operates independently, so shading of one panel does not affect others. Microinverters provide panel-level monitoring and eliminate the high-voltage DC wiring required by string inverters. They cost more per panel but can improve system yield in partially shaded conditions.
Multi-mode inverters (also called hybrid or bimodal inverters) handle both grid connection and battery storage. They can operate in grid-tied mode, off-grid mode, or mixed mode with battery backup. These inverters include a built-in battery charger and transfer switch.
Continuous power rating is the maximum power the inverter can deliver continuously. A 3,000 watt inverter handles most household loads except well pumps, air conditioners, and large power tools. Surge rating is the maximum power the inverter can deliver for a few seconds to start motor loads. A well pump may require 3 to 5 times its running wattage to start. Efficiency ranges from 85 to 98 percent, with higher efficiency at higher DC input voltages.
Pure sine wave inverters produce power identical to utility grid power, suitable for all AC appliances. Modified sine wave inverters produce a stepped approximation of a sine wave. Some devices, including variable-speed tools, medical equipment, and some electronics, may not function correctly on modified sine wave. Pure sine wave inverters are recommended for all homestead applications.