Grid interconnected solar generation systems are widely considered to be the most efficient form of small-scale, photovoltaic power. The following information explains grid-tie systems, net metering, and available incentives.
Grid-tie System Fundamentals
Grid-tie systems are designed to offset a portion of the average annual energy consumed at a home or business. In other words, investment in a solar system is proportional to the amount of energy one wishes to produce to offset utility costs.
Systems will range in cost. The final price is based on the size of the system and how the solar array is mounted. An array can be mounted on either the roof, the ground, or on a pole.
Generally speaking, 1000 watts of solar panel capacity will produce around 1050 kilowatt hours of power per year. A 3000 watt system will produce around 3150 kilowatt hours per year. If 6300 kilowatt hours per year are consumed, this system would offset 50% of the power consumed. A solar electric system half that size would cost roughly half as much, and it would produce half the power. One’s investment is proportional to power generation with a slight decrease in price per watt as the system size increases. Prices and the amount of energy produced vary based on site-specific requirements.
Trackers that follow the sun’s movement during the day produce 30 to 40% more power than fixed mount systems, and in some cases, a tracker proves to be the most cost effective solution as demonstrated by the increased return on investment.
Key requirements for a good solar site include maximum sun and limited shade for most of the day. An array southerly oriented is preferred, but avoiding shading on the panels is of greater importance than an array facing perfectly south. Tracker sites require exposure to the east and west horizons as well as the south.
The grid-tie system has few components. It is made up of solar modules, a mounting system, disconnect switches, metering, wiring, and an inverter. Solar modules produce direct current (DC) power. A home operates on alternating current (AC) power. The conversion from DC to AC is made by the inverter. Power is controlled and back-fed by the inverter into a standard household service panel. The inverter typically carries a 10-year warranty. The solar modules are warrantied to produce at least 80% of their rated power in 25 years. Solar electricity components produced today are efficient, durable, and reliable.
Grid-tied systems can also be set up as a hybrid that combines the energy independence of off-grid solar with the benefits of Net Metering. These systems are very similar to off-grid systems but the battery banks tend to be smaller since they are used less often than those in off-grid homes. During a utility failure, the system will supply power to select essential circuits. Refrigeration, well pumps, and furnaces are often chosen as circuits to backup with the battery bank. We typically choose sealed batteries that don’t require maintenance or venting for backup applications. These systems cost more than grid-tied systems since they have additional components and batteries.
Combining the benefits of being on the main utility grid with the confidence of having your own system in place, grid-tie battery systems truly provide the best of both worlds. Whether you’ve got a cabin in the mountains that has a tendency to lose power, or you just want to be sure that you’ll stay comfortable if a strong storm rolls through your area, grid-tie solar with battery backup keeps your home or commercial building powered when the main system goes down.
All work completed meets or exceeds National Electric Code and State of Vermont requirements.