Solar Energy – Frequently Asked Questions


How Does Solar Energy Work?

Q: How do photovoltaics (PV) work?

A: PV technology produces electricity directly from electrons freed by the interaction of sunlight with certain semi-conductor materials, such as silicon, applied to a PV panel. Sunlight on PV panels (or modules) produce direct current electricity, which is converted to alternating current by a device called an inverter. The inverter is wired into a main service panel where it feeds the internal power grid of a home or business. (Note: Some PV systems are not connected to the power grid and are designed to serve remote locations.)

Q: What happens on dark, cloudy days?

A: On cloudy days the solar panels generate much less electricity; the electric energy requirements of the home or business are supplied by the local electric utility grid.

Q: Do I need batteries for my PV system?

A: Unless back-up power is critical to your lifestyle or business, in the event of a weather-related disaster, for example, you do not need batteries. However, it should be noted that advances in batteries have made them a more viable option than they once were.

Q: What is the difference between PV panels and old-fashioned solar systems I often see in disrepair on some homes?

A: Old-fashioned, broken solar panels are likely solar hot water panels in many cases date back to the late 1970s. PV technology is completely different and is for the purpose of making electricity, not heating water. PV systems have a 50+ year history of reliable performance.

Q: Could a PV system become “obsolete”?

A: PV technology is evolving, but slowly. Prices are coming down because the PV industry is expanding as demand grows internationally. As with any investment in technology, floppy discs, for example, there is an element of risk that the market may change drastically. This is not in the foreseeable future for PV systems, however.

Q: Do PV systems work well in the cold?

A: Yes. In fact, silicon PV systems generate more electric energy when the temperature is lower. However, because of the shorter hours of daylight and lower angles of the sun in winter PV panels, in total, generate less energy than in summer. Also, thin film PV panels may generate less energy when cold.

Q: Are PV systems safe?

A: Solar panels are a quiet, non-polluting source of electric energy. In and of themselves, they are quite safe unless one were to fall on you. However, like all large electrical devices, PV systems generate electricity and should be treated with care and maintained in most cases by a solar professional. Panels should be installed in accordance with all state and local electrical codes.

Q: What happens during a power outage?

A: With a grid-connected PV system, the inverter will automatically disconnect itself from the utility grid when there is a power outage. This is to prevent “back feeding” the grid and putting line technicians who are working to restore power in danger. If you have a grid-connected PV system with battery back-up, it will automatically switch to back-up power with little detection. Both these systems will automatically reconnect to the electric grid once power is restored.

Q: Will adverse weather affect a PV system?

A: Most solar PV installations are designed to withstand nearly all weather conditions. Lightning, winds up to 80 miles per hour, and extreme temperatures and within the typical PV systems tolerance levels; however, those conditions would temporarily reduce the system’s energy production. Large hail and extremely high winds could potentially damage systems.


Customer-Owned Solar Systems

Q: How do I know if my site will work for a PV system?

A: Solar designers look for sites that provide an optimal southern orientation, good exposure to the sun and an adequate amount of structural support and space for solar panels to be mounted. The best location for a PV system is on a south-facing roof, but an east- or west-facing roof might also work. Flat roofs provide a base for a variety of solar modules. Locating the PV system on the ground can work with either a fixed-mount or tracking-mount (the PV panels rotate to follow the sun across the sky) system.

Q: How do I determine how large a solar system I will need?

A: The size of the system is usually directly proportional to the amount of power you use. The general rule is you should try to size your PV system equal to or less than your annual electric energy consumption.

Q: How much weight will a solar system put on a home’s roof?

A: PV systems typically weigh approximately 3-4 lbs. per sq. ft., and most roofs can accommodate two to three times that amount of weight. A roof’s load capacity is generally taken into account when assessing whether a solar system is appropriate for your home, and in the ultimate design of the system.

Q: Does a roof-mounted PV system void my roofer’s warranty and/or affect my home insurance policy?

A: It depends. Check with your roofer and your insurance agent. It is likely that the cost of your PV system will have an effect on your home insurance rates.

Q: Does cleaning the PV panels require any special expertise or equipment?

A: A garden hose is typically all that’s needed to clean PV panels.


Community Solar Systems

Q: What is Community Solar?

A: Community Solar is typically an array of PV panels located remotely serving groups of participants, rather than a single PV system mounted atop a single customer’s home or business.

Q: Why is Community Solar a viable alternative to a Customer-Owned Solar option?

A: It is estimated that less than 25 percent of roofs are suitable for solar panel installation; therefore, many home and business owners interested in solar energy do not have a way to participate. Community Solar allows a method for them to participate.

Q: If I wish to, how can I participate in Community Solar?

A: Participation methods vary greatly with each sponsoring utility. Typical methods may allow the customer to purchase a panel and then receive the energy generated or simple agree to purchase a set amount of energy monthly.

Q: What is NPPD doing to assist communities wishing to move forward with Community Solar?

A: NPPD helps communities interested in Community Solar by providing those interested with consulting expertise.


Utility-Scale Solar Systems

Q: What is Utility-Scale Solar?

A: Utility-Scale Solar is typically a larger PV installation that serves as an additional central generation source for the electric utility tasked with generating and delivering energy to a specific area with the intent of meeting the electrical needs of customers within that area. The National Renewable Energy Laboratory uses a minimum power generation capacity of five megawatts for a solar array to classify as a utility-scale system.

Q: What are the benefits of Utility-Scale Solar?

A: Utility-Scale Solar is a renewable energy form and does not contribute markedly to a utility’s carbon footprint. Utility-Scale Solar typically generates energy when it is most needed (hot summer days), effectively helping to meet system demands when they are high. Utility-Scale Solar systems are highly adaptable and can be as large as needed to meet an area’s energy demand while being as small as is practical. Utility-Scale Solar is often used as a balance to wind power’s unpredictability.

Q: Why would NPPD be interested in Utility-Scale Solar?

A: NPPD has an enviable variety of power production resources, including wind, water, coal, natural gas and nuclear. Utility-Scale Solar would add to that variety by providing additional renewable, highly green energy at key locations within the District’s electric grid.


Q: How do I determine how large a solar system I will need?

A: The size of the system is usually directly proportional to the amount of power you use. As part of the process, a representative from NPPD can assist in determining the appropriate size based on site limitations and financial parameters.

Q: Should I use a roof-mounted or ground-mounted system?

A: It depends. Roof-mounted tends to be less expensive. On the other hand, ground-mounted systems can usually be oriented and tilted to optimize energy production. Through understanding your needs and goals, NPPD or your local electric utility representative can help present an option that is optimal for you.

Q: Should I act now or should I wait to see if any major advances in technology occur?

A: Unlike some modern technologies, like silicon chips in computers, for example, PV technology has not been subject to rapid performance gains. PV technology has slowly improved over time; however, there do not seem to be any major advances on the horizon. If favorable conditions exist, it would be prudent to act now rather than wait for technological improvements to come down the pipe.

Q: How many years will a PV system work?

A: The inverter is usually the first component to break. The typical life-span of an inverter is 15-20 years. On average, a PV system can be expected to last 20-25 years.

Q: Are rebates and tax credits available to help defer the capital costs of installing a PV system?

A: At this time, there are considerable incentives available for installing PV systems. Consult with your local electric utility representative and your PV system contractor to take advantage of any federal, state or local tax incentives.

Q: If I install a PV system, how much money will I save each year?

A: There are many variables – including size of the PV system you decide to install, current electric rate your energy provider is charging, weather and amount of sunlight your area receives, orientation of your PV system, and more – when it comes to determining “payback” period. This is a topic you, your local electric utility representative and your prospective PV system contractor should discuss in depth.


Information taken from: Energy and Sun: 2015 Solar Strategy, Report and Recommendations – NPPD;;; and