A: What do we mean by photovoltaics? The word itself helps to explain how photovoltaic (PV) or solar electric technologies work. First used in about 1890, the word has two parts: photo, a stem derived from the Greek phos, which means light, and volt, a measurement unit named for Alessandro Volta (1745-1827), a pioneer in the study of electricity. So, photovoltaics could literally be translated as light-electricity. And that's just what photovoltaic materials and devices do; they convert light energy to electricity, as Edmond Becquerel and others discovered in the 18th Century.

A: When certain semiconducting materials, such as certain kinds of silicon, are exposed to sunlight, they release small amounts of electricity. This process is known as the photoelectric effect. The photoelectric effect refers to the emission, or ejection, of electrons from the surface of a metal in response to light. It is the basic physical process in which a solar electric or photovoltaic (PV) cell converts sunlight to electricity.

Sunlight is made up of photons, or particles of solar energy. Photons contain various amounts of energy, corresponding to the different wavelengths of the solar spectrum. When photons strike a PV cell, they may be reflected or absorbed, or they may pass right through. Only the absorbed photons generate electricity. When this happens, the energy of the photon is transferred to an electron in an atom of the PV cell (which is actually a semiconductor).

With its newfound energy, the electron escapes from its normal position in an atom of the semiconductor material and becomes part of the current in an electrical circuit. By leaving its position, the electron causes a hole to form. Special electrical properties of the PV cell—a built- in electric field—provide the voltage needed to drive the current through an external load (such as a light bulb).

A: A PV system is made up of different components. These include PV modules (groups of PV cells), which are commonly called PV panels; one or more batteries; a charge regulator or controller for a stand-alone system; an inverter for a utility-grid-connected system and when alternating current (ac) rather than direct current (dc) is required; wiring; and mounting hardware or a framework.

A: A PV system that is designed, installed, and maintained well will operate for more than 20 years. The basic PV module (interconnected, enclosed panel of PV cells) has no moving parts and can last more than 30 years. The best way to ensure and extend the life and effectiveness of your PV system is by having it installed and maintained properly. Experience has shown that most problems occur because of poor or sloppy system installation.

A: There are four main types of solar energy technologies:

1. Photovoltaic (PV) systems, which convert sunlight directly to electricity by means of PV cells made of semiconductor materials.

2. Concentrating solar power (CSP) systems, which concentrate the sun's energy using reflective devices such as troughs or mirror panels to produce heat that is then used to generate electricity.

3. Solar water heating systems, which contain a solar collector that faces the sun and either heats water directly or heats a "working fluid" that, in turn, is used to heat water.

4. Transpired solar collectors, or "solar walls," which use solar energy to preheat ventilation air for a building.

A: PV can be used to power your entire home's electrical systems, including lights, cooling systems, and appliances. PV systems today can be blended easily into both traditional and nontraditional homes. The most common practice is to mount modules onto a south-facing roof or wall. For an additional aesthetic appeal, some modules resemble traditional roof shingles.

A: A photovoltaic (PV) system needs unobstructed access to the sun's rays for most or all of the day. Shading on the system can significantly reduce energy output. Climate is not really a concern, because PV systems are relatively unaffected by severe weather. In fact, some PV modules actually work better in colder weather. Most PV modules are angled to catch the sun's rays, so any snow that collects on them usually melts quickly. There is enough sunlight to make solar energy systems useful and effective nearly everywhere in the USA.

Solar leases and solar PPAs are similar to renting your solar panel system. You enter into an agreement with the solar leasing company that entitles you to the benefits of the system (i.e., the energy that the solar panels generate) for the term of the contract, which is generally around 20 years.

Under these arrangements, the solar leasing company owns and maintains your solar panel system, so it is entitled to the rebates, tax breaks, and financial incentives that are available for the solar panel system. Consumers can indirectly benefit from those savings through lower electricity rates.

While the terms “solar lease” and “solar PPA” are used interchangeably on this page, and are very similar in practice, there is a key difference between the two. With a solar lease, you agree to pay a fixed monthly “rent” or lease payment, which is calculated using the estimated amount of electricity the system will produce, in exchange for the right to use the solar energy system. With a solar PPA, instead of paying to “rent” the solar panel system, you agree to purchase the power generated by the system at a set per-kWh price.

With the right size solar energy system, you can produce enough electricity to match your home's electricity use for the entire year. However, the amount of electricity your solar panels produce will vary throughout the year. Net metering (also known as net energy metering, or NEM) helps you account for these differences by crediting you for the excess electricity your panels produce so you can use it later.

While net metering is not the only way that utilities compensate homeowners for going solar, it is by far the most common: as of 2016, 41 states and Washington D.C. have mandatory net metering rules, and two more have utilities that permit the practice.

Solar energy systems typically hit peak electricity production in the afternoon, when many people aren't home using electricity. By contrast, home electricity use is typically higher in the mornings and evenings. Net metering helps you to account for these ups and downs in your day-to-day electricity production and usage.

With net metering, excess electricity is fed into your electric utility's grid when your system is producing more than you need. When this happens, your meter actually runs in reverse. When your system isn't producing enough electricity, you can draw it from your utility just as you did before you went solar. This “back-and-forth” between your system and the grid ensures that your excess production will still be used and your shortages will be met. With net metering, the excess electricity your home produces covers the times when you don't produce enough.

When your solar power system generates more electricity than you use over the course of a month, your utility bill will receive a credit based on the net number of kilowatt-hours you gave back to the grid. If you produce less electricity than you use in a given month, you must buy electricity from your utility to make up the difference. In these instances, you would pay for the electricity you use, minus any excess electricity your solar panels generated.

FICTION.

With net metering, you can receive utility bill credits for the electricity that your solar panels produce. However, you won't receive a cash payment from your utility for your excess solar electricity, no matter how much you generate. If you do generate more electricity than you use in a year, utilities in some states will let you carry credits over into future years, while others will reduce your credits.

In general, most homes will produce excess electricity in the summer months and will use more electricity from the grid in the winter. Because these variations in production are fairly predictable, your utility won't send you a monthly check when you produce more than you need. Instead, you will build up extra credits during the summer months so that you can draw from them at night and during the winter months when you need them. With the right design, your system can generate enough power to match your total electricity use for a year.

In essence, net metering is like having the grid serve as a giant solar battery. If you install an energy storage system to take your home “off the grid,” you won't have access to the benefits of net metering. In most cases, staying connected to the electric grid is your best option - while home solar battery systems can account for hour-by-hour variations in solar electricity generation, they aren't large enough to provide the seasonal “smoothing” benefits of net metering.

Thanks to net metering, homeowners are credited for the energy that their solar panels generate at the same rate that they would pay to their utility. As a result, you can save tens of thousands of dollars on electricity costs over the lifetime of your solar energy system.

If you can afford to pay your electricity bill every month, you can afford to install a solar panel system. With a $0-down solar loan, solar lease or PPA, you can finance your system and see immediate savings.

Investing in a solar panel system can deliver better returns than stocks and bonds - and now is the right time to make that investment. While solar photovoltaic technology is improving incrementally each year, financial incentives and rebates will decrease as solar becomes more popular.

Solar photovoltaic systems are a well-proven technology first invented in 1954 by scientists at Bell Labs. Today, solar panels are installed on over three million homes in the U.S.

Solar photovoltaic panels are made of tempered glass and can withstand hail, snow, rain, and high winds. They can even extend the life of your roof by protecting it from daily wear and tear.

Most solar panel manufacturers offer a 25-year power production warranty guaranteeing that their solar panels will continue to generate electricity at a certain capacity for the warranty's duration.

Solar panel systems are incredibly durable. Except in extreme circumstances, they don't need to be washed or cleaned.

Most locations in the United States get enough sunlight to produce sufficient electricity from solar panels. The most important factors to consider when you evaluate your solar panel options are the rates you pay for electricity and the rebates and incentives available to you.

When you install a solar energy system on your property, you remain connected to the electricity grid. At times when your system produces more electricity than you use, you receive credit for the electricity you send to the grid; if you need more electricity than your solar energy system is producing, you can draw it from the grid.

With the right planning, your solar panels can generate enough electricity to meet your needs over a 12-month period. If you have enough roof space to install the right size solar panel system, the power that your panels will produce will effectively eliminate most of your electricity bill.

Solar panels can be installed practically anywhere that receives direct sunshine for most of the day and is not shaded by trees or buildings. Panels that face south will produce the most electricity, but your panels can also face east or west.