How Solar Works
A residential or commercial solar-energy system uses solar PV modules, made up of photovoltaic (PV) cells, to harvest the sun’s energy and convert it into electricity that can be used to power your lights, appliances and other electrical devices in your home or business. Every day, light hits your solar panels (roof mounted or ground mounted) with photons (particles of sunlight). The solar panel converts those photons into electrons of direct current (DC) electricity. The inverter converts that DC power (the type commonly used in batteries) into alternating current or AC power. AC power is the kind of electrical power that your television, computer, and everything else uses in your home or business.
Sunlight Requirements for PV Systems
A PV system needs unobstructed access to the sun’s rays for most or all of the day in order to be effective. Shade on the system can significantly reduce energy output. Climate is not a major concern because PV systems are relatively unaffected by air temperatures, and snow cover typically melts quickly because panels are positioned directly in sunlight. Abundant year-round sunshine makes solar energy systems useful and effective nearly everywhere.
What is Net Metering?
Electricity meters can record in both directions — how much energy is being used and how much energy is being created. This allows consumers who have solar power arrays to bank excess electricity production for future credit. Any solar energy that you do not use while it is being made will go back into the electrical grid through the meter. At night or on cloudy days, when your system is not producing more than your building needs, you will consume electricity from the grid as normal. Your utility will bill you for the “net” consumption for any given billing period and provide you with a dollar credit for any excess during a given period. You can carry your bill credit forward for up to a year or your annual anniversary.
How much energy from the sun reaches the surface of the earth on average? We measure energy in units of Watt-hours. A watt is not a unit of energy, it is a measure of power.
Energy = Power x Time 1 Kilowatt Hour = 1KWH = 1,000 watts used in one hour = 10 100 watt light bulbs left on for an hour
Solar Energy that reaches earth:
- Across the entire earth = 164 Watts of solar energy per square meter reaches the Earth every 24 hours. So the entire planet receives 84 Terrawatts. Our current worldwide consumption is about 12 Terrawatts.
- 8 hour summer day, 40 degree latitude 600 Watts per square meter.
Over an 8 hour day one receives:
- 8 hours x 600 watts per sq. m = 4800 watt-hours per square meter which equals 4.8 kilowatt hours per square meter.
- This is equivalent to 0.13 gallons of gasoline.For 1,000 square feet of horizontal area (typical roof area) this is equivalent to 12 gallons of gas or about 450 KWH.