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Answers to common questions about solar power

Answers to common questions about solar power
You've got questions, we've got answers. We've organized these FAQs by topic. If you don't see the answer you're looking for, please contact us toll-free at 866-GET-SOLAR (866-458-7652), 415-655-4540, or via email.

Photovoltaic Technology

Q: How do photovoltaics work?
A: Here's a short answer: Sunlight on photovoltaic modules produces direct current (DC) electricity which is converted to alternating current (AC) by a device called an inverter, which is then wired into your main service panel where it feeds your internal power grid. For more details, click here.

Q: I know people that have broken solar panels for their homes. How is this different and why is this more reliable?
A: Good question! The broken solar panels you're referring to are solar hot water panels, in many cases date back to President Carter-era tax credits, which President Reagan promptly repealed early in his first term. The resulting slack in demand put many solar hot water panel manufacturers out of business, leaving an unfortunate legacy. Photovoltaic technology is completely different, is for the purposes of making electricity, not heating water, and has a 50+year history of reliable performance. Click here for more on the history of PV technology.

Q: How long will PV modules last?
A: Based on manufacturers' in-field experience and reliability testing, PV modules will probably last longer, and are more reliable than just about any other capital investment for your business. In 2003, BP Solar published the results of their analysis of warranty claims and reported that of more than two million modules in service over nearly ten years, approximately one-tenth of one percent were reported faulty, noting “this represents one module failure for every 4,200 module-years of operation.” Put another way, if your system has one thousand modules, you may experience the failure of ten modules in 40 years.

Q: Are there any major advances in technology on the horizon that I should hold out for? (e.g., plastics, nano, thin film, etc.)
A: Unlike the other major use of silicon – computer chips – photovoltaic technology is not subject to Moore's Law. Instead of rapid performance gains, PV technology has slowly improved over time and as such there are no reported major advances. There are some promising innovations being explored, but to our knowledge they are all in the research phase and have not been commercialized or offer improvements in cost-efficiency ($/KW generated) while greatly compromising energy density (KW generated/square foot), which makes them inapplicable for most dense, developed areas.

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System Design

Q: How do I (we/you) determine how large a system I'll need?
A: The size of the system is usually directly proportional to the amount of power you use. As part of the proposal process Sunlight Electric will perform a site assessment, analyze at least twelve months' worth of utility statements, and raise the question of near-term (3-5 year) expansion and business plans. With that information, taking into account the specifications and limitations of the components, Sunlight Electric will present recommendations for your input and feedback the goal of making sure you feel the ultimate path chosen is ideal.

Q: Roof-mounted or ground-mounted?
A: It depends. Roof-mounted tends to be less expensive as they require no support structures and are most often not visible to passersby. On the other hand, ground-mounted systems can usually be oriented and tilted to optimize production. Through understanding your business and your needs, Sunlight Electric will present a solution that optimizes for your business and your needs.

Q: What happens on dark/cloudy days?
A: Unlike the early days of solar power when systems had to be sized for peak loads, a grid-connected PV system seamlessly switches to draw from the utility grid when needed. As such, Sunlight Electric uses an annual production target, averaging out sunnier days with cloudy days.

Q: Do I need batteries?
A: Is back-up power critical to your business? For most businesses, the answer is “no” and if you don't have a back-up solution today, an ordinary grid-connected PV system will leave you in the same position. However, if you require back-up power or are looking to upgrade your business's disaster preparedness, Sunlight Electric can design a battery storage solution for your PV system to automatically switchover in the event of a power outage. Most customers inquire about batteries and ultimately choose to do without based on cost.

Q: I have plans for expansion. Can I plan for this now?
A: We frequently take into account future growth plans when designing your system. The choice of inverter can be influenced by near-term expectations about power usage and in some cases it may make sense to include excess capacity now and simply add more modules later. We'll discuss this with you and explore a variety of options to meet your needs now and in the future.

Q: How much weight will this put on my roof?
Sunlight Electric PV systems typically weigh no more than 3-4 lbs/sq ft, and most roofs can accommodate 2-3 times that amount of 'dead load' weight and your specific roof load capacity will be taken into account with our proposed design.

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Q: I hear XXXXXXX's modules are the most efficient. Wouldn't those be the best choice?
There are some performance differences between manufacturer's products and often differences within a given manufacturer's product line. As you might expect, when a manufacturer introduces a product that performs better (i.e., greater power output per square foot), that becomes license to charge more for it. As such, there's an almost perfect correlation between price and performance, the best metric is cost-per-watt, rather than absolute performance. Available space may dictate the choice of higher efficiency modules, but in every case, Sunlight Electric seeks to design the most cost-effective solution, maximizing your return on investment while minimizing the initial investment.

Q: I've never heard of the companies that make inverters (e.g., Xantrex, SMA, SatCon). How can I trust them?
A: SMA-America, located in Grass Valley, CA, is the US subsidiary of SMA, located in Niestetal, Germany, has been in business since 1981, has over 900 employees, and has sales of nearly $100 million. Xantrex is a public company located in Vancouver, BC with local offices in Livermore, CA, has been in business since 1983, has over 500 employees, and has sales of nearly $150 million. Satcon Technology is located in Boston, MA, was incorporated in 1986, has over 225 employees, is an industry leader in the development and manufacturer of power electronics and control systems for the Alternative Energy and Hybrid-Electric Vehicle markets.

Q: I've read articles noting a shortage of PV modules. Can Sunlight Electric provide the components I may want in a timely fashion?
A: It's true. Due to industry demand that continues to outstrip manufacturing capacity and semiconductor market growth putting strains on silicon feedstock supplies, PV manufacturers are behind in meeting shipments. As with most industries, major buyers tend to have greater influence. Sunlight Electric continues to meet our customers' needs with relatively little delay, 8-10 weeks at most.

Q: What about foam insulation-backed PV panels?
A: These products have advantages and disadvantages. The primary advantage is they require very few roof penetrations and the insulation is a nice-to-have side benefit, though most commercial buildings that require insulation already have it. There are two major disadvantages: First, foam-backed modules suffer from a lack of air space under the modules for cooling. Specifically, framed modules from 160-200 watts DC have as much as 5% greater AC yield than their foam-backed counterparts. Second, foam-backed modules offer limited tilt angles available (~10°), further lowering their output.

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Subsidies & Economics

Q: What rebates are available?
A: Rebates vary from year to year depending on the funding for particular programs and the size of the PV system. Sunlight Electric will give you the most current information and include that in your proposal.

Q: How do we apply for a rebate?
A: Relax, that's our job. We believe that the easier we can make the purchase of a clean photovoltaic system, the more people will buy them, the better off we'll all be. That's why we work to make the process as easy as possible, and handle all the rebate and utility company paperwork for you.

Q: Can the rebate request be rejected?
A: In most cases, rebate reservation requests are processed in 6-8 weeks. When funds are not available, projects are waitlisted. No evaluation of the recipients are made beyond making sure the components of the system are on the “approved” list.

Q: Is financing available?
A: The best source of financing is usually the bank or finance company that you currently work with. If you like, we're happy to make arrangements with a number of independent mortgage brokers we've worked with on other projects.

Q: How much are these systems and how much money will I save each year? (Or, how long will it take to pay back my investment?)
A: The size of the system is the largest determinant of the price, and the savings rise accordingly. In most cases, the payback period for the investment in a photovoltaic system is 5-7 years.

Q: What's the impact on my property taxes?
A: Photovoltaic systems are exempt from property taxes in California.

Q: We don't own the property on/in which we operate. Can we still go solar?
A: Yes, it's relatively commonplace for property owners to allow their tenants to make improvements in their facilities.

Q: Since the return on investment hinges on selling power to my utility, how can I be confident this will be accurately accounted for?
A: The power you generate is metered by your inverter and the utility meter tracks power in both directions – both power you buy and power you sell back to the utility. Plus, you can track your production and the power you export via our online monitoring software. Finally, you'll receive a monthly statement from your utility company. All these provide ample reassurance that the accounting will be done, as it has been done for the nearly 15,000 interconnected photovoltaic systems all across California.

Q: What are the critical assumptions for modeling ROI?
A: The key drivers are savings from power no longer purchased and the value of the state and Federal subsidies.

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Q: Will a roof-mounted system void my roofer's warranty?
A: We frequently coordinate our work with roofers to ensure warranties remain in force and the PV system installation also comes with a 5-year warranty which includes roof integrity.

Q: My building's roof needs replacing soon. Does it make sense to integrate the installations?
A: Yes. If you're planning to replace your roof in the next few years, it may make sense to move that up and install the PV system at the same time as the new roof is going on.

Q: What if my roof needs repair after the PV system is installed?
A: Spot repairs are easily accommodated as any since module is secured with only four 5/16” hex bolts. Non-penetrating ballasted systems can also easily be moved to accommodate repairs.

Q: What kind of county/city permits will I need?
A: We always need an electrical permit from the city or county and some require a building permit as well. Sunlight Electric and our licensed installers will handle all of this, from applications to inspections.

Q: How long will my installation take?
A: This depends mostly on the size of the system, site access, and the distance between the array(s) and the main service. In general, figure one week for each hundred modules to be installed.

Q: Will installation interfere with my normal business operations?
A: Most work is conducted on the site of the array installation (roof or ground) so your operations will likely not be impacted. We coordinate our efforts with your team, from deliveries, securing equipment, to crane usage. For example, we always schedule the final tie-in around your schedule.

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Q: What are the maintenance procedures and costs?
A: Solar PV systems are solid state technology, have no moving parts and require no maintenance beyond cleaning, which can typically be done with a garden hose. Most systems should be cleaned 2-4 times a year, concentrated in the drier seasons. Systems in agricultural areas will likely require monthly cleaning. (We have an automated washing solution – ask us about it.)

Inverters are also solid state and require little to no maintenance beyond regularly checking the cooling fan outlets and cleaning when necessary. Mounting hardware is either aluminum or stainless steel and is rust-proof.

Q: Does cleaning the modules require any special expertise or equipment?
A: A garden hose will typically do, though some customers prefer to use a high-pressure sprayer from the ground when the array is accessible.

Q: What parts will break first?
A: The inverter(s), which typically have a useful life of 15-20 years, will be the first thing to fail.

Q: What about rust and oxidization?
A: All hardware is made for outdoor use and is made of either rust-proof stainless or galvanized steel or aluminum.

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Q: Someone told me that the energy required to make PV panels is greater than they will every produce. True?
A: Glad you asked! We've heard this one before. Numerous studies indicate it takes 2-3 years to generate as much power as is required to manufacture photovoltaics, and the Environmental Working Group's Green Energy Guide reports an energy return on investment for photovoltaics of 9-to-1, greater than most other electricity sources (i.e., coal: < 8:1, wind: 5:1, nuclear: <5:1, biomass: 3:1).

Q: I hear manufacturing PV panels creates toxic by-products and waste. True?
A: Another good one, which we've also heard before. There's less documentation on this than the energy return on investment question, suggesting it's probably not an issue, but the Environmental Working Group's Green Energy Guide reports the manufacturing and operation of photovoltaics creates far less emissions than any other source of electricity analyzed.

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Photovoltaic Technology
System Design
Subsidies & Economics