The technology, price and aesthetics of photovoltaic systems have improved to the point that PV arrays are now the most popular choice for homeowners, versus years ago when thermal solar products for heating water were often the first consideration. PV cells convert sunlight directly into electricity, and the cells are typically contained in panels that are installed on a home’s roof; a group of solar cells is called a module or panel, and a group of panels is called an array. A typical PV installation for a 2,000-2,500-square-foot house in New England that uses air conditioning would include an array of 20-40 PV panels each with micro-inverters (or DC optimizers with a central inverter) to convert the solar-harnessed electricity to AC electricity that can be used in the house or sold back to the power company.