Components for your PV (Solar Electric) System

Inverter

Solectria Inverter on a Prewired Power Panel

An inverter takes direct current (DC) from batteries and turns it into alternating current (AC) which is used to run most common electrical loads. There are two main classes of inverters, grid-tied or grid-capable and off-grid, standalone units. Off-grid inverters require batteries for storage. Straight grid-tied inverters don’t use batteries and grid-capable inverters can work either with or without batteries depending on system design. There is a wide range of available inverter features suited to differing system needs and situations. Some inverters have integrated AC chargers so that they can use AC power from the grid to charge the batteries during periods of low sun. Inverters with integrated AC chargers can also be used in conjunction with fossil fuel-based generators for battery charging or running very large loads. Off-grid inverters meant for whole-home usage must have appropriate conduit boxes and accessories that enclose all live wiring. Usually, whole-home inverters are rated to produce 2,000 Watts continuous power or more. Off-grid inverters come in two flavors: those producing modified sine wave current and those producing pure sine wave current. Some appliances (compressors or other inductive loads) and many sensitive electronics (cordless battery chargers, computers, stereos, etc.) will not function properly on modified sine wave power. Off-grid inverters can cost anywhere between $100 to $3,000 depending on size and type. A straight grid-tied inverter connects directly to the utility grid without the use of batteries. With these inverters, when the grid goes down the PV system also goes down to protect service linemen from injury due to unexpected “live” lines during outages. A grid-capable inverter can both connect to the grid and use batteries, which allows for the possibility of back-up power during outages. Grid-connected inverters also generally produce 2,000 Watts or more and cost about $2,000 to $4,000.