Frequently Asked Questions

Q: Where can PV modules be installed?
Q: Is my roof appropriate for a PV installation?
Q: What is the optimal tilt angle for modules in MA and NY?
Q: How big are the solar modules?
Q: Do we have enough sun in New England for PV?
Q: How much energy will my PV modules produce?
Q: What are the environmental benefits of a PV system?
Q: What are the costs, and why is PV so expensive?
Q: How long will it take for my PV system to return my investment?
Q: What are REC's, or Renewable Energy Certificates, aka Green Tags, aka...?
Q: Can I add more capacity to my system in the future?
Q: Do I need to be connected to the power grid to use PV?
Q: Does a grid-tied system require batteries to store electricity?
Q: Will my grid-tied PV system serve as emergency backup in case of a blackout?
Q: Which photovoltaic modules do you use in your installations?
Q: What about PV roof shingles?
Q: Does BPVS install or repair solar hot water systems?
Q: Does Massachusetts or NY have any tax incentives for renewable energy?
Q: Will I realize significant savings on my next electric bill?
Q: How long do your PV systems last? What if my system needs service?
Q: I heard that more energy is required to produce a PV module than that module will ever produce in its' lifetime. Is that true?
Q: Is it true that production of PV modules is hazardous to the environment, and that there are hazardous materials in PV modules?
Q: The computer I bought two years ago is now "obsolete". Is this going to happen to my PV system components?
Q: I have heard about many problems with the inverters used in PV systems. Is this a reliable component of the system?
Q: What if there is a small amount of shading on my site at different times of the year? How much could this affect the performance of a system?
Q: My roofs face east and west; does this mean my site fails?
Q: All I want is a quantity of modules. What's your price for...?
Q: I want to buy modules or a PV system from a web supplier? Is this a good deal, will you install them?
Q: I heard BPVS is famous for energy efficiency and conservation retrofits; do you still do that work?
Q: What about snow covering the PV array? What about array maintenance?



Q: Where can PV modules be installed?
A: PV can be installed anywhere that receives unobstructed sunlight. Roof installations generally work very well because the modules are close to the point of use. Modules can also be installed on ground, pole, or wall mounts.

Q: Is my roof appropriate for a PV installation?
A: The ideal roof is a south-facing, slanted roof with no shading on the area where the modules will be located. PV can be installed on roofs with other characteristics, but the efficiency may be lower. Please call BPVS to discuss your buildings details and a site assessment.

Q: What is the optimal tilt angle for modules in MA and NY?
A: There is an old "rule-of-thumb" circulating that says the optimal angle of inclination for absorbing solar radiation is latitude of the location plus 15 degrees for winter optimization, or latitude minus 15 degrees for summer optimization. This rule was adhered to by many solar thermal installers, optimizing their systems for winter production, and the use of the rule resulted in many of the dramatically tilted solar thermal panels you see on peoples homes in New England (Most of MA is near 42 degrees north latitude, putting winter optimal inclination at 57 degrees). However, in order to truly address the question of what is the optimal tilt angle of any panel that must be structurally incorporated with or near your home in the North East there are a number of factors to be considered beyond solar performance; wind loads, snow loads, snow shedding, and aesthetics are all important considerations. Furthermore, optimal solar performance is not as simple as differentiating between summer and winter; if your system is grid-connected and you are primarily interested in deferring carbon production you may want to optimize for summer while another grid-connected system owner might prefer to optimize for year round production, and if you are a system owner in a remote location without a grid connection you may want to optimize for winter. Commercial and Institutional system owners may have different stipulations for solar performance optimization than residential system owners. Finally, in terms of solar performance, it is important to note that the difference in solar performance that is exhibited while varying module inclination between 5 and 30 degrees (28 degrees being the year-round-optimum for MA) is not more than 8%, and between 12 and 30 degrees it isn't more than 4%. Between 17 and 45 degrees (covering the range for most residential roofs), you will make use of 98 to 100% of all available sunlight. BPVS will take all factors into account when we design your system, and will work with you to arrive at the system design that is truly optimal.

Q: How big are the solar modules?
A: 1 kW of solar modules will occupy an area of approximately 11 square meters (118 square feet).Each ASE-300 watt module is 50 inches wide by 76 inches high.

Q: Do we have enough sun in New England and NY for PV?
A: Yes as do most regions on Earth! A system rated at 2 kW will produce about 2,400 kWh annually in New England & NY. This is enough to provide one quarter of the average New England home's electricity. For homes with efficient appliances and lighting, and conservative energy users, a 2 kW system may provide much more of the energy than the household needs. Because New England uses more energy in summer time when photovoltaic production is at its peak, the clean electricity produced by grid-connected systems is especially valuable.

Q: How much energy will my PV modules produce?
A: A 1 kW PV array installed in Massachusetts or New York should produce on the order of 1,200 kWh per year.

Q: What are the environmental benefits of a PV system?
A: Photovoltaics produce clean, free energy. When connected to the grid, this clean energy displaces conventionally produced energy and its carbon dioxide, nitrogen oxide, sulfur dioxide, mercury and heavy metal particulate emissions. Even better, a PV system in this region will produce its maximum amount of power in the summer when electricity demands on the grid are at their highest, stabilizing the grid and displacing the dirtiest emissions. In Massachusetts, every Kilowatt Hour of energy produced by PV displaces about 1.39 lbs of Carbon Dioxide, 3.0345 grams of Sulfur Dioxide, 0.9117 grams of Nitrogen Oxides, and 2.449 mg of Mercury.

Q: What are the costs, and why is PV so expensive?
A: Residential PV installations cost roughly $10 per peak Watt of installed power capacity, a number that has been dropping over the years. Larger systems generally cost between $7.50- $10.00 per peak watt. The ultra-pure silicon used to make PV cells is the single largest expense involved in PV systems. The crystal growth process is very costly, but essential to the effectiveness of photovoltaics. The energy needed to manufacture the PV modules installed by BPVS will be reclaimed within the first fourteen months of their operation, however. When we examine the external costs to the environment and to future generations for conventional power, PV is a bargain.

Q: How long will it take for my PV system to return my investment?
A: A brutally conservative analysis, for a utility interactive system, at present value, with Massachusetts and New York incentives puts the return of investment at between 20 and 40 years. Without these incentives, return of investment could take as long as 80 years. You may see estimates addressing this issue that are much more liberal; by manipulating factors and speculating about changes in utility provider structuring and market prices for RECS, one could arrive at values as low as 5-15 yrs.We encourage potential owners of PV systems to accept conservative estimates toward return of investment, and to commit to renewable energy in their life based on the environmental benefit. The price of electricity will likely go up, and incentives offered by utility providers and legislatures may decrease, disappear or emerge where they don't presently exist. Speculating about the details of these potential changes is difficult since energy is such a volatile commodity. It is certain that PV's external values are beginning to be monetized.

For stand alone systems, there is no easy answer. In some off-the-grid cases, the cost of a PV system may be less than the cost of running cable and hooking up to the grid. In this case, PV is an immediate savings. In other cases, the PV system cost may be comparable to or more than a grid connection, and you can think of paying for a PV system as paying your entire utility bill up front, minus the costs of system maintenance. Maintenance costs for a stand-alone system will be greater than for a utility interactive system due to the necessity for local storage of power (batteries).

Q: What are REC's, or Renewable Energy Certificates, aka Green Tags, aka...??
A: A REC or "Green Tag" is effectively a certificate representing the "green" attributes of the electrical energy generated via a renewable energy source such as photovoltaics, micro-hydro turbines, wind turbines, etc. REC's enable the green attributes of the energy to be separated from the energy itself such that they can be traded on an open market using the same metrics as electricity. Why and how does this market exist? Every kilowatt hour your system produces whether you use it or it is exported to the grid accrues to making a REC which is equivalent to 1 megawatt hour or 1000 kilowatt hours. The most frequent end-purchasers of REC's are utility providers who must adhere to a Renewable Portfolio Standard (RPS), which is a set of requirements stipulating the allowable mix of electrical energy the utilities may supply in terms of minimum percentages of energy from renewable sources.

Not all states have developed RPS requirements, and thus markets for RECs do not exist in all states (NY is one of these states). In states with an RPS requirement, like Massachusetts, utilities cannot purchase enough renewable generating capacity from electricity suppliers to meet the requirements, and so are allowed to purchase the attributes of renewable energy. Alternately since supply of renewable energy and thus RECS is constrained utilities pay a penalty for not meeting the RPS. Can you sell your REC's directly to the utility? No; one REC amounts to the green attributes of one megawatt-hour of electrical energy, the amount of energy generated by a 1 kW pv system in almost a full year. RECS are authenticated in our area on the New England Generational Information System -NE-GIS and are traded on the wholesale market for electricity. That is where buyers and sellers meet.

It is possible for small renewable generators to register their RECS and trade them on the open market but it is a cumbersome process and must be done annually. You cannot register anything less than 1 REC (1 megawatt-hour or 1000 kilowatt hours) and cannot carry over one year's production to the next. This is why there are REC aggregators, who work like brokers of the energy attributes, collecting them in small amounts of kilowatt-hours, registering these as RECS on the NE-GIS and selling them to buyers on the wholesale market. You can find contact information for REC aggregators at www.dsireusa.org.

Some REC aggregators have developed an alternate market outside the mandated Renewable Portfolio Standard. They purchase your clean energy attributes in small amounts, register them and those of others as RECS on the NE-GIS and then sell Green electricity directly to consumers, in effect retiring the RECS and offering a clean energy mix for purchase at a premium. The Massachusetts Technology Collaborative which manages the Massachusetts Renewable Energy Trust Fund is actively involved in making sense and assuring the integrity of RECS markets. You can learn much more at www.masstech.org.

What is the BPVS policy on RECS? We recognize that the true costs to society and the environment for "dirty" power are not reflected in your electric bill. To the extent that RECS help balance that inequity we support this infant market for green electricity and the Renewable Portfolio Standard. Thus every PV system we install includes a new "revenue grade" sealed kilowatt hour meter to tally your clean energy production and assure you eligibility to sell your RECS. We guarantee the accuracy of the meters we supply. We are happy to pull our meter so your local inspector or a utility engineer or a RECS aggregator can see that we have wired the meter base to Code and thus safely and just as importantly have not "gamed" the wiring to allow the meter to measure more electricity than the PV system can truly produce. Our system handbook explains fully how you can read this meter and we only use digital read out meters so you do not have to figure out kWh production from multiple analog dials.

BPVS considers it a conflict of interest to go any further and so we do not accept RECS as part of your payment for the PV system hardware and installation or in any other form of transaction including donation. The minimum purchase price for one REC is now (Spring 2005) $50.00 or 5 cents per kilowatt hour but they can trade in large blocks at much higher rates; we've heard as much as $650.00 per REC in volatile market moments. If you make a deal with a RECS aggregator and they in turn require you to install their meter and automatic telephonic or modem reporting equipment we will install that equipment for you to National Electric Code standards and to only register the production of the PV system. We will not guarantee the accuracy of their metering equipment or the warranties of the RECS aggregator. We do not recommend particular RECs aggregators but do urge you to consult the information on the websites listed above before you enter into a contract with a RECs aggregator. We do not give out or sell the names of our customers to anyone (so if you are a RECs aggregator reading this, please stop calling us).

You do not have to sell the "green attributes" of your electricity production. Most of our customers are not bothering with the RECs for two reasons: they feel the value of their resource will improve as the market matures or believe that in short, virtue is its' own reward.

We'd prefer a simpler market force for the benefits of clean energy from small renewable generators. The activity around RECs, their emphasis on tradable attributes, is reminiscent of the sale of indulgences in the Middle Ages. At policy meetings in Massachusetts BPVS has urged a strategy for valuing highly only the exported kilowatt hours a PV system produces. Thus a PV system is interconnected behind the utility meter as it is now and your home or business uses the clean electricity first, deferring purchase from the grid. However we recommended excess electricity you export to the grid be compensated well above retail rates and those decremented kilowatt hours be measured on the utility meter and read and reported by the utility. In this way the PV system owner has an incentive to conserve electricity and export as much as possible. It would make larger PV systems more cost effective capturing economies of scale; it would ensure that real green electricity is compensated and measured. The cost of course would have to be recovered in the rate structures and in diminished subsidies for fossil fuel and nuclear power. Our position is politely and understandably ignored but some concede privately that a transparent mechanism like this is inevitable.

Regulators and policy makers are beginning to see that the verification of clean energy production should be regulated strictly. To us it makes no sense for solar kWh meters to be supplied and read by unregulated entities whether a PV contractor, the PV system owner, or a RECs aggregator. Utility companies follow strict standards on the metering of electricity you purchase, are audited, and have in place the infrastructure to accurately read and report the electricity production of distributed generators like PV systems. The protocols and incentives in place in Germany ( which is the largest market for PV systems in the world) do just that. The State of Washington is now considering a variant of the German model originated in Aachen and generally known as the Aachen plan.

RECs are certainly a positive market incentive especially for large commercial projects. The Northeast is on the right track in pioneering clean energy market forces like RECs; we need a national policy of renewable energy production incentives guaranteed for the long term like the Aachen plan.

Q: Can I add more capacity to my system in the future?
A: Yes, assuming you still have available space for added modules on your roof or on your property grounds. Most of the system components we use (inverters, esp.) are designed to create modular systems. If, in the design stages of your first ever pv system, you have a strong feeling that you may be interested in adding modules to the system in the future, we can incorporate very subtle design details that will make adding on in the future a simple and less costly project. If you presently have a system, and wish to add to it, please contact us and we'll help you decide what the add-on will entail.

Q: Do I need to be connected to the power grid to use PV?
A: No. If you are not connected to the grid, you can use what is called a stand-alone PV system. This includes a battery bank to store energy for use at night and cloudy days. BPVS is a recognized leader in stand-alone design and installation. PV is versatile, so stand- alone systems may power a full size remote home or a single water pump in a remote pasture.

Q: Does a grid-tied system require batteries to store electricity?
A: No, a grid-tied system is connected directly to the electric grid. This means that the grid in effect acts as a battery. If at times your system generates more energy than the home is using, the excess energy is sent back into the utility network and your utility bill is credited. This is called net metering.

Q: Will my grid-tied PV system serve as emergency backup in case of a blackout?
A: That depends. A standard grid-tied system shuts down when the utility grid goes down and will not provide you with emergency power. This is a safety feature of the system. A hybrid system is possible in which you also have a battery bank and isolating transfer equipment that can provide you with power safely should the grid go down. These system designs are a less efficient use of the PV resource; battery bank storage and charge maintenance introduce wasteful losses. Hybrid systems are much more expensive and require significant maintenance. BPVS will provide you with objective data on various emergency power designs and we do have several customers for whom the benefits of a hybrid system outweigh the losses and maintenance inherent in storage batteries.

Q: Which photovoltaic modules do you use in your installations?
A: Whenever possible, BPVS uses solar modules made in Massachusetts, supporting the local economy. The two Massachusetts manufacturers are RWE Schott Solar Inc. of Billerica and Evergreen Solar of Marlboro. The Schott and Evergreen silicon wafer manufacturing processes are some of the most resource efficient in the world, using much less raw silicon in production than competitors who saw wafers from silicon ingots. The Schott process, developed at MIT and called Edge Defined Film Fed Growth (EFG), has been in continuous production since 1978. Their ASE-300 watt module is our favorite. Evergreen Solar is using a similar process called String Ribbon Growth, and has a 12 year track record. We use their EC-100 and 115 watt modules in some applications.

Q: What about PV roof shingles?
A: BPVS does not feature these products. New England & NY weather demands robust pv arrays. The multiple wire connections and other design features of the roof shingle and metal roof products don't meet our standards of reliability and waterproofing.

Q: Does BPVS install or repair solar hot water systems?
A: No, but solar hot water systems can be quite cost effective. Please go to the Northeast Sustainable Energy Association's Sustainable Yellow Pages at www.NESEA.org for firms specializing in Solar Domestic Hot Water.

Q: Does Massachusetts or NY have any tax incentives for renewable energy?
A: Yes, Massachusetts has an income tax credit for individuals who install renewable energy systems (solar or wind power) for their primary residences. The credit is 15% of the cost of the system, including installation, up to a maximum of $1,000. For commercial owners, BPVS will explain other federal and state incentives. Additionally, the purchase of a PV system to be installed on a primary residence is exempt from Massachusetts sales tax. See our Grants and Incentives page for more information on State incentives.
(These statements are for informational purposes only; further details are available at www.dsireusa.org. The Customer should consult a professional tax advisor on eligibility and application for these tax incentives.)

Q: Will I realize significant savings on my next electric bill?
A: We'll do the calculations for you based on your usage and the capacity of your PV system. Many customers do realize large reductions and renew their efforts to conserve as a result of being both a generator and consumer. Overall , dollar to dollar per kWh, conventional electricity is cheaper than PV; it takes a long time for monthly savings to re-pay the capital investment of a PV system.

Q: How long do your PV systems last?
A: The inverter comes with a five year warranty, and a life expectancy of fifteen years: the PV modules come with a 20 year warranty and a life expectancy of 50 years in our region. Our workmanship warranty is five years, and includes waterproofing. We're committed to our warranty services and are happy to provide references to customers we first served with PV installations in the 1980's.

Q: I heard that more energy is required to produce a PV module than that module will ever produce in its' lifetime. Is that true?
A: The modules we use will replace their embedded energy in the first twelve to fourteen months of generation. This misinformation you hear about PV is typically referring to very old studies when the technology was under development and manufacturing processes did not benefit from the technological advancements or economies of scale that exist today.

Q: Is it true that production of PV modules is hazardous to the environment, and that there are hazardous materials in PV modules?
A: The production of the modules from RWE- Schott Solar using their proprietary, conscientious production techniques, is environmentally benign, and no toxic or hazardous materials are part of the completed product. Evergreen Modules do contain small amounts of lead solder. As with most industry, there are materials and chemicals used in PV module production that are designated as toxic by the EPA, however research conducted by the National Renewable Energy Laboratory (NREL) concluded that through careful engineering of manufacturing processes PV manufacturers have reduced the environmental risks such that they are far less than those in most major industries. The manufacturers of the modules we use are dedicated to recycling, and safe disposal of hazardous chemicals and materials required by the manufacturing process. What's more they have shared their expertise with other manufacturers globally through Industry Associations and National Research Institutes. Most of the media myths referring to hazardous materials in the PV industry are generalizing about the entire technology based on PV cell research, some solar cells used in space applications, and a few products not carried by BPVS.

Q: The computer I bought two years ago is now "obsolete". Is this going to happen to my PV system components?
A: No. Since the early years of the development of PV systems as power production for building electrical systems, few changes have been made in the various "black-box" components and their roles in system operation. Changes made to the electronics within some components (inverters, charge controllers, mainly) have improved their performance and reliability. The modules themselves have changed very little in structure, or materials, though small improvements in efficiency have been made and, hopefully, will continue to be made. The rate of improvement and magnitude of change in efficiencies is nowhere near that of the computer related semi-conductor industry.

Q: I have heard about many problems with the inverters used in PV systems. Is this a reliable component of the system?
A: Today, yes. We have examples of inverters in installations done by BPVS's founder that have been operating, trouble free, for over 25 years. In the early to mid-1990's there were many inverters on the market that were problematic, and many failed after startup. BPVS provided replacements and warranty services for the few we encountered. At present, we have a number of very reliable, and well performing inverters to choose from depending on the type and size of the installation. Inverter failure is really no longer a concern in the PV industry.

Q: What if there is a small amount of shading on my site at different times of the year? How much could this affect the performance of a system installed at my location?
A: When we initially consider a site for feasibility, shading is a primary concern. We’ve found that for many people the perception of shading is under or over estimated. Call us for instructions on accurately assessing your "solar window". The PV modules we use are equipped with bypass diodes, a feature to lessen the effects of shading on system performance, but even so shading can significantly reduce annual production. At 20% or more of annual sun hours shaded we will advise against installing a PV system. It is essential to select a site and mounting configuration that precludes all but the most minimal shading (under 12% is best) from stationary obstructions. Trees, chimneys, dormers, utility poles and other buildings are typically the greatest concern among residential sites. Even utility lines and limbs of deciduous trees in winter can provide significant shading. On commercial and institutional roof sites chillers, vent pipes and ductwork are often the culprits and restrict array locations.

Q: My roofs face east and west; does this mean my site fails?.
A: No, in our service territory a PV array facing true east or true west on a steep roof will see a 15% penalty in production compared to true south. Low pitched east and west facing roofs fare much better. We can set array mounts askew to the roof orientation or mount the array as an awning on the south wall of a building. In our area arrays should never face north of true east and true west.

Q: All I want is a quantity of modules. What’s your price for...?
A: There is a worldwide shortage of PV module manufacturing capacity for the demand this year and it will remain tight through 2008 so because we're one of the oldest businesses in the technology this has been a frequent phone call and e-mail query. We have a consistent supply of modules for our NY and New England customers under contract and seeking system installations this year and for years to come. We do not market quantities of modules to re-sellers.

Q: I want to buy modules or a PV system from a web supplier? Is this a good deal, will you install them?
A: This too has become a common question. Unfortunately there is a lot of mediocre equipment and poorly designed system kits available on the web by auction and web retailers. We have installed these systems in special cases and have had to modify them to meet Code, always resulting in higher costs for the customer than if they just contacted us before buying.

Q: I heard BPVS is famous for energy efficiency and conservation retrofits and consulting; do you still do that work?
A: Our firm has a long history in this field and pioneered instrumented energy retrofits in the region. We still serve selected new residential and commercial customers. If you have an interesting project close to Adams, Ma please call us.

Q: What about snow covering the PV array? What about array maintenance?
A: Sometimes winter snows are so heavy they will block enough light to prevent electricity production. A light snow cover will diminish capacity. Typically snow melts off arrays quicker than on roof surfaces. We do not recommend cleaning snow off roof top arrays unless you can do it from the ground with a snow rake made of plastic or wood. It is not necessary and may scratch the glass to vigorously scrape snow or ice off the array. Clearing most of a heavy cover will be sufficient as direct sunlight will melt the rest. Some of our stand alone customers selected a pole mount or wall mount system to make it easier to remove snow. They need every watt hour of production during the winter low sun period of the year. Grid connect customers however can bear with a week or two of snow cover on their array since 70% of their annual power is made between late Spring and early Fall. Our system handbook goes into this and general maintenance thoroughly as well as instructions for when you need to re-roof. 2005 is our twentieth year in business, we will call you to offer an array check-up on the fifth year after installation and every five years thereafter to check the integrity of wire connections and waterproofing and to wash the module glass for a nominal hourly charge. These checks have shown us that our wiring techniques and waterproofing are meeting the tests of time and that normal rainfall keeps modules quite clean. Our workmanship warranty covers the first five years free. We're happy to offer you an annual service contract but only recommend this for PV systems with batteries.

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