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A well-designed PV system needs clear and unobstructed access to the sun's rays for most or all of the day, throughout the year. You can make an initial assessment yourself, and if the location looks promising, your PV provider has the tools to trace the sun's path at your location and determine whether your home or business is a good site for PV.
The orientation of your PV system (the compass direction that your system faces) will affect performance. In the United States, the sun is always in the southern half of the sky and is higher in the summer and lower in the winter. Usually, the best location for a PV system is a south-facing roof, but roofs that face east or west may also be acceptable. Flat roofs can also work well for solar systems because the PV modules can be mounted flat on the roof facing the sky or mounted on frames tilted toward the south at the optimal angle. To make the best use of your PV system, the PV modules must have a clear "view" of the sun for most or all of the day-unobstructed by trees, roof gables, chimneys, buildings, and other features of your home and the surrounding landscape. Note that even though the area where a system is mounted may be unshaded during one part of the day, it may be shaded during another. If this is the case, then this shading may substantially reduce the amount of electricity that your system will produce. If a rooftop can't be used, your solar modules can also be placed on the ground, either on a fixed mount or a "tracking" mount that follows the sun to orient the PV modules for maximum performance. Other options (used most often in multifamily or commercial applications) include mounting structures that create covered parking or provide shade as window awnings. Do you have enough area on your roof or property? The amount of space needed by a PV system is based on the physical size of the system you purchase. Most residential systems require as little as 50 square feet up to as much as 1,000 square feet. Commercial systems can be even larger. If your location limits the physical size of your system, you may want to install a system that uses more-efficient PV modules. Greater efficiency means that the module uses less surface area to convert sunlight into a given amount of electric power. PV modules are available today in a range of types, and some offer more efficiency per square foot than do others. What kind of roof do you have, and what is its condition? Some roof types are simpler and cheaper to work with, but a PV system can be installed on any type. Typically, composition shingles are easiest to work with, and slate is the most difficult. In any case, an experienced solar installer will know how to work on all roof types and can use roofing techniques that eliminate any possibility of leaks. Ask your PV provider how the PV system affects your roof warranty. If your roof is older and needs to be replaced in the very near future, you may want to replace it at the time the PV system is installed to avoid the cost of removing and reinstalling your PV system. Panels often can be integrated into the roof itself, and some modules are actually designed as three-tab shingles or raised-seam metal roof sections. One benefit of these systems is their ability to offset the cost of roof materials.
As a starting point, you might consider how much of your present electricity needs you would like to meet with your PV system. For example, suppose that you would like to meet 50 percent of your electricity needs with your PV system. You could work with your PV provider to examine past electric bills and determine the size of the PV system needed to achieve that goal.
You can contact your utility and request the total electricity usage, measured in kilowatt-hours, for your household or business over the last 12 months (or consult your electric bills if you save them). Ask your PV provider how much your new PV system will produce on an annual basis (also measured in kilowatt-hours) and compare that number to your annual electricity demand to get an idea of how much you will save. In the next section, we'll provide more information on estimating how much you will save. To qualify for "net metering" in Vermont, your PV system must have a peak generating capacity of not more than 15 kilowatts (15,000 watts). One optional feature you might consider is a battery system to provide back-up power in case of a utility power outage. Batteries add value to your system, but at an increased price. As you size your system, you should consider the "economies of scale" that can decrease the cost per kilowatt-hour as you increase the size of the system. For example, many inverters are sized for systems up to 5 kilowatts, and if your PV array is smaller (say 3 kilowatts), you may still end up buying the same inverter. Labor costs for a small system may be nearly as much as those for a large system. Therefore, it's worth remembering that your PV provider is likely to offer you a better price to install a 2-kilowatt system all at once, than to install a 1-kilowatt this year and another similar system next year-because multiple orders and multiple site visits are more expensive.
The value of your PV system's electricity will depend on how much you pay your utility for electricity and how much your utility will pay you for any excess that you generate. Because all Vermont utilities now offer net metering (and so pay the full retail price for your excess electricity), your calculation may be fairly easy because you and your utility will each pay the same price for each other's electricity. You can use the calculation box to roughly approximate how much electricity your PV system will produce and how much that electricity will be worth. Keep in mind that actual energy production from your PV system will vary by up to 20 percent from these figures, depending on your geographic location, the angle and orientation of your system, the quality of the components of your system, and the quality of the installation. You should realize that even if an estimate is accurate for an average year, actual electricity production will fluctuate from year to year due to natural variations in weather. Calculating Electricity Bill Savings for a Net-Metered PV System
Energy from the PV system = (kW of PV) x (kWh/kW-year) = kWh/year Divide this number by twelve if you want to determine your monthly energy reduction. Energy bills savings = (kWh/year) x (Residential Rate)/100 = $/year saved (Residential Rate in this above equation should be in dollars per kWh; for example, a rate of 10 cents per kWh is input as $0.10/kWh.) For example, a 2-kW system in Vermont, at a residential energy rate of $0.10/kWh will save about $200 per year (1,000 kWh/kW-year x $0.10/kWh x 2 kW = $200/year).
There is no single answer, but keep in mind that a solar rebate and other incentives may reduce the cost. Your system's price will depend on a number of factors, including whether the home is under construction or whether the PV is integrated into the roof or mounted on top of an existing roof. The price also varies depending on the PV system rating, manufacturer, retailer, and installer. The size of your system may be the most significant factor in any equation measuring your costs against your benefits. Small, single PV-panel systems with built-in inverters that produce about 75 watts may cost around $900 installed, or $12 per watt. These small systems will offset only a small fraction of your electricity bill. A 2-kilowatt system that will offset the needs of a very energy-efficient home may cost $16,000 to $20,000 installed, or $8 to $10 per watt. At the high end, a 5-kilowatt system that will completely offset the energy needs of many conventional homes may cost $30,000 to $40,000 installed, or $6 to $8 per watt. These prices, of course, are just rough estimates, and your costs will depend on your system's configuration, your equipment options, and other factors. Your local PV providers can provide you with estimates or bids.
Incentives have been available intermittently to Vermont residents who install grid-tied systems. Check our incentives page for up to date information. As of July 1, 1999 all equipment purchased to construct and install a net-metered renewable energy system is exempt from the state's sales tax. This tax exemption provides Vermonter's with an extra incentive to produce green power. In 1998 the Vermont legislature passed H.605 requiring electric utilities to offer net metering for all electric utility customers. Net metering makes it easier and more cost-effective for Vermonters to generate some of their own electricity. When your PV system generates more power than you need, the meter runs backwards resulting in an even swap for the grid power that you use at other times. If a net metering customer uses more electricity than is generated, the customer will pay the utility only for the difference. If, at the end of the year, a net metering customer still has a credit on the bill that credit reverts to the utility. In essence, you receive full retail value for all the power that your PV system generates up to the level of your household's total consumption. Net metering customers must pay the same customer service charges and other monthly fees required of other consumers. To qualify for net metering in Vermont, PV systems must have a peak generating capacity less than or equal to 15 kilowatts (15,000 watts). For additional net metering information, including an application for a certificate of public good (required for all net-metered systems), and the Public Service Board's interconnection safety and technical requirements, you can link to the Department of Public Service web-site at http://www.state.vt.us/psd/ee/ee20.htm. Retail Sales Tax Exemption Sales Tax- Starting July 1, 1999 all equipment purchased to construct and install a net metered renewable energy system in Vermont is exempt from the state's sales tax. This five percent savings provides an additional incentive to help Vermonters produce their own green power. During the last legislative session, attempts were made to expand the sale tax exemption to include off-grid PV and solar hot water system; however, it did not pass. Vermont legislators and renewable energy proponents will continue their efforts at future legislative session in extending the sale tax credit to include solar hot water and off-grid solar electric systems. The current bill can be viewed at the following site: http://www.leg.state.vt.us/docs/2000/bills/passed/H-705.htm. If you have specific questions on eligibility of renewable energy systems for sales tax exemptions, or on claiming a tax exemption ask your solar installation professional or contact the RERC. The U.S. government also provides financial support for PV technology through a tax credit for commercial uses of solar energy. This energy investment credit provides businesses (but not individuals or utilities) with a 10% tax credit and 5-year accelerated depreciation for the cost of equipment used to generate electricity by solar technologies. Burlington Electric Department (BED) Burlington Electric Department's SunWise Program was started in 1999, offering Burlington's residents with technical assistance and financial incentives for the installation of PV and solar hot water systems. BED will continue to offer SunWise program services in 2000, providing technical assistance, project management and financing for utility- interactive PV and solar hot water systems. To find out more about the SunWise program, call BED at (802) 865-7337.
A portion of Vermont's electricity comes from nuclear and fossil fuel-burning power plants, which produce emissions including long-lived radioactive wastes, greenhouse gases and other air pollutants, including those responsible for acid rain. By using renewable solar energy to meet a portion of your household's electric needs, you can significantly reduce your household's contribution to the release of these pollutants. |
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