photovoltaic systems

PV systems have recently gained strong popularity because of lowered equipment costs coupled with ever increasing electric rates. Additionally, Virginia residents enjoy some of the most generous financial incentives in the country to install PV. Unlike solar hot water systems, which are essentially a plumbing device, PV is an electrical system hard-wired to your electric circuit breaker box. The core of a PV panel uses silica wafers, when exposed to sunlight generates direct current (DC) electricity. The more solar modules a PV system has, the more electricity is generated. This DC electricity is then “inverted” into alternating current (AC), which can be used for household use to reduce (or even eliminate) you electric bill.

Sunpower and GE Photovoltaics and BP Solar


Net metering is the practice of using a single meter that tracks both what you’ve “taken” from the grid and what you’ve “fed-back” into the grid. When your PV system generates power beyond what your house is consuming, this surplus power is “fed” back into the utility grid, making your electric meter actually spin backwards. If you generate more electricity than you consume at the end of the month, you receive full retail credit and possibly cash from your utility provider (depending on their policy). Dual metering configurations use two separate meters to track power from the grid and to the grid individually for billing purposes. Either way, most homeowners will install a solar hot water system in addition to a PV system because this will allow the PV system to satisfy a higher proportion of household electric demand, making the PV system even more cost-effective.

PV systems typically fall into the following configurations:

  • "Grid-Tied" PV systems use special inverters to allow electricity to flow safely back into the electric grid, augmenting the utility company’s electric capacity. Grid-tied PV systems may have battery back-up capability (with additional cost), but are not necessary to the system. Grid-tied PV systems are the most cost effective way to generate your own "green" renewable energy from the roof of your home.
  • "Off-Grid" or stand-alone systems are just that. They are completely independent of a utility company and almost always use some kind of electric back-up system for surge power and night time electricity needs.

PV systems are sized by wattage capacity during full sun, or maximum insolation. In Virginia, a straight grid-tied PV system will typically range in capacity from 2 kilowatts to 5 kilowatts and generate approximately 300 and 750 kilowatt-hours per month, respectively and significantly reduce your electricity costs with clean, green, renewable energy generated on your own roof.

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