What does a typical PV system look like?
A typical PV system consists of solar cells connected electrically to form a module that can measure two to four feet wide and four to six feet long. Many interconnected PV modules are called an array. An array is often mounted on the roof of a building, facing south at an angle, so the modules receive the maximum amount of sunlight. Another typical feature of a PV system is the inverter, which changes your electricity from direct current to alternating current so it can be used by most standard appliances and computers. Batteries may also be added for emergency backup in the event of power outages or in cases where your PV system is not connected to utility power lines. 
Image above shows a residential Grid-Connected Photovoltaic System.
1. solar panels 2. inverter 3. breaker box 4. home power and appliances
5. meter 6. utility power grid. (1) Solar Electric or PV modules convert sunlight to electricity. The PV modules generate DC electricity - or direct current - sending it to the inverter. (2) The inverter transforms the DC power into AC electricity for ordinary household needs. (3) Existing electrical panel distributes solar electricity and utility power to (4) loads (appliances). For systems with a battery backup (optional), the inverter also regulates the charge of batteries. The electricity stored in the batteries can be used at night or during blackouts.
A valuable feature of photovoltaic systems is the ability to connect with the existing power grid which allows owners to sell excessive electricity back to the utility with a plan known as (5)
Net Metering. At times when you are not using all of the electricity produced by your system, your meter will spin backwards selling the electricity back to the (6) utility power grid at retail rate.
How is power measured from a PV or solar electric power system?
o The capacity of a PV system is stated in terms of the number of watts, kilowatts or megawatts it produces in standard sunlight conditions. A good estimate for New York is that each kilowatt of PV capacity (alternating current) will produce approximately 1,000 to 1,300 kWh (kilowatt hours) per year, depending on the angle at which the solar panels are mounted. Thus, a 3 kW system will generate about 3,000-3,900 kWh per year, or about 50-60 percent of the average residence’s electric consumption.