Solar Questions & Answers

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• What is renewable energy?
• What does "energy conversion efficiency" mean?
• What are the environmental benefits of solar energy?
• What is the major concern of using solar energy?
• When will renewable energy replace coal and other energy sources?
• How do I use the electricity from a solar system?
• Will a solar system produce enough energy?
• What happens at night?
• What if it's a cloudy or rainy day?
• In what temperatures will a solar system operate?
• What does a solar system consist of?
• What types of materials are used in making a solar / PV (photovoltaic) cell?
• How much space does a solar system need?
• How long will it take to install a solar system?
• What are the factors to consider for installing a solar system?
• What long does a solar system last?
• What are the typical problems during the operations of a solar system?
• How much electricity does a solar system produce?
• What is Net Metering?
• Who is eligible for Net Metering?
• Can I use my current electric meter?
• Do I need to be connected to the grid?
• Do I need batteries?
• Do I need a generator?
• How can I know whether my solar system works?
• Can I add a battery backup after installation?
• How can I calculate the savings of a solar system?
• Is my roof right for a solar system?
• Can my roof support the weight of a solar system?
• Will my property taxes increase?
• How much does a solar hot water system cost?
• What about insurance for a solar system?
• Are there tax credits available if I install a solar system?
• What are the property tax benefits of a solar system?
• What's the ideal situation for using solar panels?
• Solar is so expensive, shouldn’t I wait until the technology is cheaper?

Q:What is renewable energy?

Renewable energy is any energy that is self-replenishing. Examples are wind, solar or geothermal energy.

Energy conversion efficiency means the amount of energy produced in proportion to the amount of energy consumed. Today's typical PV systems are between 7% to 17% efficient. Many PV systems degrade a little bit (i.e., lose efficiency) each year upon prolonged exposure to sunlight. For comparison, a typical fossil fuel generator has an energy conversion efficiency of about 28%. As the solar technologies advance, this efficiency gap is becoming smaller and smaller every year, and therefore making solar energy more affordable.

Every kilowatt-hour of electricity produced by renewable energy displaces the same amount of electricity produced by conventional power generation methods that consume fossil fuel. This means less CO2, SO2, and NOx in the air. Renewable energy production also reduces suspended particulates we usually call smog. As we all know, smog is a significant health problem during the hot summer days.

Cost is still the #1 concern. Currently, using solar energy technologies require a significant initial outlay. In nearly all cases, this initial cost is high, and can only be recovered through substantial fuel savings over the life of the product (typically 15-30 years). However, to encourage the spread of solar energy, governments and manufacturers around the world provide rebate and incentives to reduce, sometime significantly, the cost of using solar energy. Today, in many areas, such rebates and incentives make solar energy affordable, and even profitable. Please SolarCentral.org's Benefits and Cost page to find out the details of these rebates and incentives.

Renewable energy is still more expensive in comparison to traditional energy source, such as coal and fossil-fuel-based energy. However, the price of fossil fuels is continuing to rise and the price of renewable energy continues to decline. Peak oil production is right around the corner, and people are increasing their demand for clean energies. In Japan, Germany and some developing countries, renewable energies are already competitive due to a number of market forces. These same market forces are becoming increasingly relevant to consumers in North America. If considering environment benefits, renewable energy will save our world.

The electricity generated by a solar system works just like the electricity delivered by electricity company. After passing through a component called an inverter, the direct current (DC) electricity generated by the solar panels is converted to alternating current (AC), the type of electricity that you access through the outlets in your home.

For average residential customers, a solar system can produce 10% - 50% of their annual energy needs. The exact amount of electricity generated depend on where you are living. Also system size impacts production. The size of a solar system that is right for you depends on how big your investment is and how much un-shaded roof space is available.

Since a solar system requires sunlight (not heat) to produce electricity, it does not generate electricity at night. Utility electricity company will continue to supply electricity to houses at night if a solar system is connected with the utility electricity network or a battery backup is used.

A solar system performs optimally when it is sunny. It generate electricity during cloudy or rainy days too, but at a lower level as some of the sunlight is blocked.

A solar system typically operates in temperatures ranging from -13 to 122 degrees Fahrenheit. A solar system is an electronic device that generates electricity directly from sunlight. Output drops off as the system gets hotter. In summer months, the increased daylight hours increases production.

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

The most widely used material for PV cells is silicon, a semiconductor. The silicon is "doped" (that is, it has a certain amount of impurities placed into the silicon crystal) with either boron or phosphorus to give it the properties needed to be a PV cell and give up electrons when exposed to light. The photons of light (photons are actually small particles of light) "knock" the electrons out of the outside band of the silicon atom and that is what creates the PV effect.

A typical solar system requires about 7 to 8 square feet for each dollar of your monthly electric bill. For example, if you spend $100 per month on electricity, your solar system would be about 700 to 800 square feet. This figure varies depending upon your electric rates.

It will typically take two to three days to install a residential rooftop solar system by a professional installer. For commercial installations, consult your solar installer.

Geographical location (more sunshine is better), air quality (clear places are better) and the facing of panel (facing the sun is better) are the major factors.

A well-designed and maintained solar system will operate for more than 20 years. The solar / PV module, with no moving parts, has an expected lifetime exceeding 30 years. Typically, solar installers provide 25 years of warranty.

Experience shows most problems occur because of poor or sloppy installation. Failed connections, insufficient wire size, components not rated for dc application, and so on, are the main culprits. The next most common cause of problems is the failure of electronic parts - the controller, inverter, and protection components. Batteries will fail quickly if they are used outside their operating specification.

The amount of electricity generated by a solar system is dependent upon several factors, primarily system size, orientation of the system and shading. The rule of thumb is that a solar system using 120 square feet of solar panels will generate 1,000 - 1,440 kWh per year.

Net Metering is the agreement between an owner of a solar system and the local Utility Company that allows the owner to spin the meter backwards, and therefore selling extra electricity to the Utility. The owner can be a net producer or net consumer based on the electricity produced and used. Exact provisions vary with each state, but the effect is to allow you to generate excess power during the day, and use it at night, without needing batteries.

In USA, 26 states have established law requiring utility company supporting Net Metering. Everybody is eligible for Net Watering if you are an electricity customer in one of those states, and some of your electricity is generated by solar or wind energy, or a combination of both, with a system capacity of one megawatt or less, and your electric generating system is located on your premises and connected to the grid.

Most residential and small commercial customers have simple meters that are bi-directional, capable of turning in both directions. Some electric utilities may want two meters for net metering, one to measure electricity going from the grid to your home or business, and one to measure the excess going from your system to the grid. If your electric utility wants two, unidirectional meters, they must pay for them, not you. If you enter into a time-of-use billing agreement, you must purchase a bidirectional time-of-use meter. Contact your electric utility for more information.

It depends. If you want to be qualified for solar rebate you need to be connected to the grid in most states in USA. While you generate the bulk of your own electricity during the peak hours of daylight and demand, your utility will seamlessly take over and continue to supply your electricity at night and on very cloudy days. If you decide to include battery storage, the additional cost for the battery system will not be covered by the rebate.

You do not need batteries if you are tied into the public utility grid. Essentially your utility company stores your solar electricity for free. Batteries would only be necessary if you need power during blackouts or if you are not connected to the grid.

You do not need a generator if you are installing a solar system. A generator can be integrated to work with solar to power your house for a certain number of hours in case of a black out.

Since solar technology is motionless and noiseless, a meter is required to keep track of how much electricity a solar system is producing. The inverter display can show you how much power is produced at any given time. Also, if the disc on your solar meter is rotating, your solar system is generating. There are also monitoring services that help you monitor and manage your solar system.

Yes. If you start with some battery backup, it is easy to add more. However, if you start without a backup, it will be rather expensive to add batteries due to the high cost of adding a different type of inverter. Systems without battery-backup use a different inverter than those with battery backup.

A 10% efficient solar system in most areas of the United States will generate about 180 kilowatt-hours per square meter. A solar system rated at 1 kilowatt will produce about 1800 kilowatt-hours a year. Most PV panels are warranted to last 20 years or more (perhaps as many as 30 years) and to degrade (lose efficiency) at a rate of less than 1% per year. Under these conditions, a solar system could generate close to 36,000 kilowatt-hours of electricity over 20 years and close to 54,000 kilowatt-hours over 30 years. This means that a solar system generates more than $10,000 worth of electricity over 30 years.

A solar system can be installed on many different types of roofs. They include a flat composite, tar and gravel, bitumen, composite shingle, cement tile, or metal roof top. Solar panels are usually installed parallel to the roof surface. For this reason the orientation of your roof is important. South facing roofs offer the most annual production, while east and west facing roofs will produce less. However, west facing roofs produce more power during "peak" times when power can be worth more money.

Solar panel and mounting equipment add very little load to your roof. In most cases a solar system will add less than 4lb per square feet of load to the roof. Virtually all modern construction is designed to support loads far greater than this. Some older homes may require some structural work prior to installing a system. However this is very rare and is still an exception even for older homes.

No. Despite the fact that your property value will increase, there is legislation that prevents your property taxes from increasing.

A solar hot water system costs between $3,500 and $5,000 installed. It can reduce your hot water heating bill by up to $100 per month. The payback period for an investment in a solar thermal hot water system is three to five years. After that, the savings are all yours and systems have been known to last longer than twenty years.

A home-owner insurance company is obligated to insure a solar system, just as to other household items.

Yes. Over 25 states in USA offer a personal income tax credit for the installation of a solar system. For the latest tax credit and other government incentive programs information pertaining to your state, visit www.dsire.org.

Many states in USA allow for the exclusion of a solar system from property taxation as long as the property does not change ownership. In other words, while the market value of your house will go up with the installation of a solar system, however, it can be excluded from your property's assessed value. For the latest information pertaining to your state, visit www.dsire.org.

The following situations are ideal for considering to use a solar panel system: has flat roof, or a roof facing southward, or building a new home.

It is possible that there will be a cheaper, better technology in the future but how much money will you pay your utility company in the meantime? More than likely, it will be more money than you save on the new technology. The time is now to make an environmental impact and invest in green energy.