How Solar PV Works
Photovoltaic (PV) devices generate electricity directly from sunlight using a process that naturally occurs in some materials. Within a certain class of crystals, electrons are freed when tiny packets of light from the sun — called photons — are absorbed.
These electrons that are freed travel through a circuit as electricity. This process does not emit any harmful pollutants, making solar a clean, safe source of energy.
Solar PV systems are groupings, or “arrays,” of modules wired together along with an inverter and utility meter to produce electrical power. The panels are commonly protected with a 25-year warranty and are designed to withstand hail, lightening, and high winds.
The PV system is tied to the utility grid to ensure a steady supply of electricity. Any excess electricity the system produces will be fed back to the grid. To move “off-the-grid,” a battery backup system will be needed to supply electricity at night.
A PV system is typically installed on a roof, but can also be installed on the ground as a “ground-mount” system.
Residential solar systems are mounted to the roof with a racking system designed to secure the panels while not damaging your roof. They are generally not adjustable and designed to position the solar panels at a consistent elevation above the surface to which they are mounted. Residential systems can be mounted to all roof types including shingles, tiles, and metal roofs. Commercial systems can be mounted on a flat roof with a ballasted roof mount, which does not penetrate the surface. Systems can also be mounted on the ground if there is enough un-shaded area available.
Solar Panel or Solar Module
Solar panels are comprised of many individual solar cells. Solar cells are made from layers of silicon, phosphorous (which gives the negative charge),and boron (which provides the positive charge). The solar cells are wired together in a circuit. When photons from the sun strike the surface of the solar panel, electrons are knocked out of their atomic orbits and released into the electric field. The circuit of solar cells then pulls the free electrons into a directional current (also known as DC electricity). This entire process is known as the Photovoltaic Effect. Multiple panels are required to meet the electricity requirements of an average household. The DC electricity generated from the solar panels is then sent to the inverter.
Solar inverters convert the electricity from solar panels, DC (direct current) into AC (alternating current), which is the type of power used in most homes. The inverter will allow the system owner to see exactly how much DC electricity is being generated by the solar system. Once the electricity has been converted from DC to AC, it is then sent to the utility meter.
When a building has a PV system installed, there is a PV meter installed to track the system’s energy generation (output) in kilowatt hours (kWh). The utility company replaces the existing building meter which tracks energy supplied to the home or business with a new dual-read billing meter (net meter). This dual-read meter captures two different readings: 1. The amount of energy supplied to the building by the utilities distribution grid and 2. Any excess energy generated by the solar PV system that was not used by the building at the time it was generated . This excess energy goes back into the distribution grid and is termed “push back.” This energy is “credited” to the customer’s bill.
Solar 101 Menu
Got questions? Let us help.
We are here to help homeowners and businesses along the process of going solar. If you have any questions throughout the process, please call our office or send us an email.
If you are interested in solar, fill out an application and we will distribute it to three local solar installers who will contact you to provide you a quote.
How big is a solar PV system?
The average residential system is 5 kW, which is about 20 panels. Systems come in many sizes and vary depending on your energy goals. The solar installer will review your current and average energy usage to design a system that will produce the correct amount of power to suit your needs.
Is the rebate running out?
Due to an increase in solar applications, the CPS Energy commercial and residential rebates have already been reduced from $2 to $1.60 per watt.
The rebates are expected to run out by the end of the 2015 fiscal year, if not earlier.
The federal tax credit is set to expire in 2016; it is unclear if it will be renewed.
How much is solar worth?
Currently, CPS Energy uses net metering to apply value to solar generated by your system.
Through net metering, CPS Energy credits your utility bill 1-for-1 with the amount of energy generated by your system. The current price of electricity is $.097 per kilowatt-hour.
Each kilowatt produced by your system cancels out a kilowatt-hour you used from the grid. This allows you to have a source of electricity whenever you need it, not just when your system is generating electricity.
How long does the system last?
Solar panels last a very long time. Most companies offer a warranty for 20-25 years, but the system is expected to last longer. The panels are designed to withstand hail, hurricane force winds, and rainstorms.
Do I need to have a new roof?
If your roof is in new or good condition, then there is no need to get a new roof. If you have an older roof that needs to be repaired, you will want to do it at the time the PV system is installed. This is because if you put your solar PV system in place and then have to replace your roof, you will have to pay extra to remove and reinstall your PV system.
Do the panels need to face south?
PV modules should be oriented geographically to maximize the amount of daily and seasonal solar energy that they receive. In general, the optimum orientation for a PV module in the northern hemisphere is true south. However, your modules can face up to 45º east or west of true south without significantly decreasing its performance.
Can my HOA prevent me from going solar?
A Homeowner’s Association cannot legally stop you from going solar unless there is still an undeveloped plot in your neighborhood.
I want to be off the grid. What does that entail?
Well, it is pretty difficult to be completely off the grid. In addition to the solar system, you will need to purchase a battery to store excess energy for use at night. Batteries are still an expensive technology. Additionally, you cannot take advantage of the CPS rebate if you are not connected to the grid. Going off grid will cost at least $30,000.
How much does it cost?
The cost of solar depends on the size of your house. Currently, the rebate amount in the CPS Energy service area is $1.60 per watt up to $25,000 or 50% of the cost of the system, whichever is less. Once the rebate is credited, a 30 percent federal tax credit can be applied to the remaining balance. The average residential home (2,200 to 2,500 square feet) installs on average a 5 kW system. After rebates, the average price for the entire system ranges from $8,000 to $10,000 depending on installer and your house. Keep in mind this is just an estimate based on the average of contracts signed. Your quote will vary.
Is financing available?
Some solar installation companies offer financing. However, there are also a variety of lending institutions in San Antonio that provide home improvement loans.
San Antonio Credit Union
Eloisa Riojas, Loan Originator, Home Loan Production
Randolph Brooks Federal Credit Union
If you take out a loan from one of these institutions, please mention our name when doing so.
Will I make money off of my PV system?
If your solar system overproduces, meaning it generated more electricity than you used from CPS Energy, the amount the utility will pay you is $.02 per kilowatt-hour. Since CPS Energy does not pay the full price of electricity ($.097) for what you over-produce, you will not make a significant profit from this.
Do the solar panels need to be mounted on a roof?
Panels are often mounted on the roof, but can also be mounted on the ground if the space is available. Keep in mind, wherever the panels are located needs to be free of shade. Roof mount systems are most common in residential installations.
What happens if it’s raining or cloudy? Does shade matter?
The panels can still produce if it’s cloudy, but the production will not be the same as it is when the sun is shining. A permanent shade caused by a tree could seriously restrict the productivity of your panels. Your solar installer will make your panels are not shaded.
How long does it take to install a solar system?
The entire process of receiving an estimate, site survey, approval, installation, and inspection takes about 6 weeks.
How do I know that the solar installers are good companies?
The CPS Energy-approved solar companies that participate in the program must become professional members in our organization as well as maintaining professionalism and experience within the city. The companies vary from large electrical and renewable energy businesses to small businesses that specialize in energy efficiency.