What is Solar Electricity?

 Solar photovoltaic (PV) systems, also referred to as solar electric systems, capture sunlight energy and convert it into electricity. PV systems can be used to power everything in your home from lights and appliances to an electric vehicle.

How Does PV Work?

The graphic below explains how solar electricity is produced, where the energy flows, and the bill-crediting mechanism known as “Net Energy Metering”.

 

1. Individual photovoltaic (PV) cells are embedded onto panels. Sunlight striking the panels is chemically converted into direct current (DC) electricity.
2. The DC electricity goes to an inverter that transforms it into alternating current (AC) for household use.
3. The utility meter records the net amount of energy (kWh) consumed. When the system creates more electricity than needed in the home, the meter will "spin backward" and the excess electricity is released onto the electric grid and 'credited' to your utility account. These credits help offset the cost of kWh usage at night or on cloudy days when PV systems are not producing as much electricity.

How can I compare PV panels?

PV panels can be evaluated by cost, efficiency and power capacity. Typically the higher the power rating and efficiency, the higher the panel cost. Discuss with your contractor about the expected performance of each type of panel to understand if the kWh production from a higher efficiency rating may offset the higher cost of the panel.

For more information on evaluating PV panels visit the EnergySage Solar Marketplace.

How do I choose an inverter?

There are two types of inverters: central and micro.

Central inverters – One individual inverter per array. This is the classic technology that is installed with most solar systems. The kW size of these inverters is determined by the total number of panels linked to it. Therefore, any plans to increase the system size due to future appliance additions, should be considered during the initial stages of design. While the main drawback of central inverters is performance limitations, such as shading tolerance, this can be improved with the installation of power optimizers.

Microinverters – One individual inverter per panel. Microinverters allow overall systems to be more tolerant to shade by allowing electrons to bypass any shaded cells, avoiding a severe drop in total production and allowing for more flexible system placement. They more easily allow for future panel additions by simply adding an additional microinverter for each additional panel.

Comparison of Inverter Options

	Central Inverter	Central Inverter with Power Optimizers	Microinverters
Tolerant to shade	No, one or two shaded panels can affect the power output of the total array	Yes, a mechanism bypasses the shaded panel	Yes, shade from one panel will not affect the other panels in the system
Flexibility in system design	Yes, installing a higher wattage inverter can allow for adding panels in one array (azimuth and tilt may be a factor)	Yes, panels can be installed in multiple tilts and orientations	Yes, the tilt and orientation of one panel will not affect other panels in the system
Cost	$	$$	$
Easy system size increases*	No, the central inverter is sized to the capacity of the entire system	No, the central inverter is sized to the capacity of the entire system	Yes, since each panel has its own inverter, your options are open for system expansion
Warranty	10-12 years	10-12 years for the central inverter, 25 years for the power optimizers	25 years
Panel selection	Unlimited	Unlimited	Limited

*If you think you may want to add panels to your solar PV system in the future, it may be more cost-effective to install the infrastructure (racking, wiring, conduit, upsized inverter size) during the original installation.