Frequently Asked Questions


1. What is PV?

"PV" is an acronym which stands for "photovoltaic," the production of electricity from light. The photovoltaic effect is an aspect of the photoelectric effect. It is defined as the conversion of electromagnetic radiation to electrical voltage by a specific material. 

2. What is a solar cell?

A solar cell is a single piece of photovoltaic material for  incorporation into a larger module. Usually it looks like a piece of  blue stone or plastic with connection leads for an electric circuit. The solar cell is built with several layers, including at least two semiconductor layers--often designed to absorb light at different wavelengths. Two conductive layers draw off the charge, and often the conductive layers will be metallic or transparent metallic oxide such as zinc oxide. An anti-reflection layer is on top and a on the bottom is a  reflection layer. On top may be an encapsulating layer as well, which is commonly glass to protect the material. There are trade-offs between efficiency, product complexity, manufacture cost and product lifetime depending on the PV cell design. 


3. What is the history of PV?

1839: Edmund Becquerel discover the photovoltaic effect using copper oxide in an electrolyte. 

1860s: Willoughby Smith discover the photoconductive properties of selenium. 

1870s: W.G. Adams and R.E. Day further investigate the photovoltaic properties of selenium. 

1874: Charles Fritts makes the first solar cell from gold and selenium. Efficiency was less than 1%. 1887: The photoelectric effect is discovered in metals by H. Hertz. 

1904: Albert Einstein publishes his monograph on the photoelectric effect.  

1954: Gordon Pearson discovers the photovoltaic properties of silicon. Pearson, Charles Fuller and Darryl Chapin work to improve the efficiency of the silicon solar cell and efficiency is improved to 4% and then 6%.

Late 1950s: NASA determines that solar cells are an ideal energy source in space. Serious funding of PV research begins. 

1959: A 10% efficient commercial solar cell is produced by Hoffman Electronics. 

1962: The Telstar communication satellite is powered by solar cells.  

Late 1970s: The OPEC-inspired oil embargo unsettles the first world nations who begin funding many forms of alternative energy research, including PV.  

1979: Jimmy Carter installs 32 solar panels on the White House, saying "A generation from now, this solar heater can either be a curiosity, a museum piece, an example of the road not taken, or it can  be a small part of one of the greatest adventures ever undertaken by the  American People." Late 1990s: With rising consciousness and concern about the availability, consumption and consequences of modern energy resources, interest, funding and production in photovoltaics begins to rise exponentially. 

2008: The 46 MW Moura photovoltaic power station in Portugal and the 40 MW Waldpolenz Solar Park in Germany are completed. Solar power continues trend of doubling in world output every 2-3 years, at which rate it will be the dominant energy source on the planet by the end of the century. The US Department of Energy has established the  goal of generating 10-15% of the nation's energy from solar sources by  2030. 

2006 - 2010>>>: The US Federal Government, State Legislatures and local utility companies commit several billion dollars in funding and incentives to construct massive solar arrays and for rebates and incentives for homeowners to go solar, following and building momentum in the worldwide trend with Germany, Japan, Spain, China, Taiwan and many other countries. 

4. How do photovoltaics work?

To describe it at the simplest and most practical level, you shine light on a solar cell and you get electricity. 

On a slightly more sophisticated level, photons of a high energy are absorbed by semiconductor material creating electron-electron hole pairs which come under the influence of an electric field and are conducted through an external circuit.  

5. What types of PV cells are there?

Besides using a variety materials, those materials are also used in different ways. All of the materials are semiconductors. Some exotic materials have  even been utilized, though mostly in the laboratory. Sometimes more  than one semiconductor is used in a single device. The commonly seen forms of photovoltaic devices are: 




thin film 


One of the significant trade-offs in these different forms is  the cost of production. As an example, amorphous silicon bypasses the  expensive step of crystal ingot production. Another trade-off is the efficiency of the resulting device.  

6. What constitutes a complete PV system?

It depends upon your circumstances and what you are trying to do. A backwoods system running off the grid will be different from a grid  tied system in an urban area. Likewise, a standalone installation will  be different from an integrated construction PV shingle system. In its  simplicity, a complete PV system essentially consists of your solar  panels, the simple equipment used to mount them (whether to your roof or another location), an inverter which takes the solar DC and adapts it  to your household AC, and the wires and conduits that join it all  together and to your electric panel (for the typical grid-tied systems) or to batteries (for off-grid or back-up systems). 

7. What is an Inverter?

An inverter is an electric device which converts direct current [DC] to alternating current [AC]. Solar cells produce a direct current. Most of the electrical  devices we commonly use expect a standard AC power supply. An inverter takes the DC from the solar cells and creates a usable form of AC. In addition, an Inverter may also be connected to the electric grid and/or a battery backup system.

8. What does a Grid Connected (grid tied) system mean?

A PV power system, by its very nature and function, produces energy during the daytime only, while energy is used day and night. How does one deal with this situation? There are two solutions, depending upon the specifics of the  installation. Either one delivers extra power during the day into a reservoir, whether a battery backup system or one uses an inverter which can also be connected to the electric grid. In the latter case, one delivers excess power into the public grid during the day, and then withdraws it at night. This is called a grid-tied system.

9. What is a hybrid system?

It is a combination photovoltaic and solar thermal system. Usually  water is circulated behind the solar cells to both collect heat and to cool the cells. This can result in a substantial increase in system efficiency.  

10. What is Net Metering?

Your solar panels generate electricity which is brought to the mains coming from your utility power meter. Any excess power you generate will feed back into the utility meter/grid and drive your power meter backwards. This is called Net Metering. Effectively you will be paid the going price for your electricity up to the amount of energy you use per billing cycle. Any excess energy you generate may be credited at a lower rate or not at all. This arrangement is mandated in the USA by federal law [PURPA, Public Utilities Regulatory Policy Act (1978)]. Space permitting and with a properly sized PV system, your electric bill can be essentially zeroed out or, in the least, greatly reduced. 

11. How does solar system connect to my house? 

It is wired into your existing electrical panel via a breaker.  

12. What type of roofs can solar panels be installed on? 

PV can be installed on any roofing material. Some ceramic, cement, and metal tile may increase the installation cost. 

13. How can I tell if my house/building is suitable for Photovoltaic Panels? 

Several things will need to be evaluated to determine whether your home is a good solar site or not, such as its orientation, the space available, any shading, and your current electricity usage. An ideal site will be one with adequate south-facing roofs that have little or no shade. Variations on that will reduce the productivity of the system,  but even imperfect solar locations can still likely benefit from a well-designed system.

14. What do I do if I need to re-roof? 

In most cases, the solar panels can be easily removed and re-installed. If the roof is a tar and gravel design, it may even be possible to simply tilt the panels up and then re-tar and gravel.  

15. How do I determine what size of system I need? 

Any size solar system will make an impact on your yearly power consumption. The bigger the system, the bigger the impact. To figure out how much of an impact, you can find the total number of Kilowatt-hours you used in the last 12 months from your power bills, or by annualizing your average daily consumption (also found on most power bills). Part of Moore Solar's on-site inspection and estimate involves going over your power usage, your specific needs, consulting with you on ways to increase efficiency in your home and sizing your solar system  accordingly. 

16. How long will a home solar power system last? 

Most home solar power systems are predicted to last between 25-35  years. Most manufacturers guarantee that after 25 years your solar panels will output about 80% of the electricity they did in their first year of installation.   

17. What if a majority of my utility bill is comprised of natural gas charges? 

Solar electric systems offset only the electricity portion of your utility bill. It won't help reduce your natural gas bill. However, if you're paying anything over $100 or $150 per month for electricity only, solar will make a lot of economic sense for you. To reduce gas charges,  you might consider a solar thermal system.

18. What if I just moved and am uncertain how much electricity I will use in my new home? 

Moore Solar & Green Contruction can provide a very accurate and specifically tailored design for you based on your past electricity usage patterns, your new home size and predicted future electricity usage.  

19. Will a home solar power system increase my property taxes? 

No - property taxes are unaffected. Even though your property's value will increase, there is legislation that prevents your property taxes from increasing. In California, that specific legislation is Section 73 of the California Revenue and Taxation Code. This code provides a property tax exclusion on most types of solar power systems,  including home solar power systems.

20. Can my homeowners association (HOA) stop me from installing a home solar power system on my home? 

Most often not. In unfortunate circumstances, an HOA may try to,  but in many states this is not allowed. In California specifically, the California Solar Rights Act states that homeowners associations (HOAs),  governments, and other organizations cannot stop you from installing a  home solar power system. They may ask you to modify the design and/or location for aesthetic reasons, but can even only do this legally so long as the changes don't significantly impact your solar electricity  production (a decrease greater than 10%) or cost you more than $2000.