utility customers throughout the U.S. who were tired of the
high cost of electricity have taken advantage of generous
rebates and tax credits which are available for the
installation of solar electric systems on their homes and
For example, the
State of California is currently offering a cash rebate of
$2,200.00 per kilowatt of installed solar power as well as a
Federal 30% tax credit ! Many other state are participating in similar
programs. Click here to
find out whether or not your state offers a rebate program
And unlike the
old solar systems of yesteryear that only produced hot water,
these new systems actually produce electricity. Clean
reliable electricity to run lights, TVs, pumps, refrigerators,
computers and many other appliances, all with free energy from
a solar system produce electricity for your home.
solar electric system consists of several solar modules that
contain many individual solar cells. A solar cell or photovoltaic cell is made of special materials
called semiconductors, the most common semiconductor material
which is used in the manufacture of a solar cell is known as
silicon. When a light source strikes a solar cell, a portion
of it is absorbed by the semiconductor material. The absorbed
light energy knocks electrons loose, allowing them to flow
freely. See illustration below.
Picture of an individual
A solar electric module consists of an aluminum framed sheet
of highly durable low reflective, tempered glass that has had
individual solar cells adhered to the inner glass surface.
These individual solar cells are wired together in a
series/parallel configuration so as to obtain the necessary DC
voltage and current.
The back of the solar module is
then sealed by a long lasting weather proof material
such as Tedlar shown in white in the following image and a
weather proof junction box or flying leads are attached so
that an electrical connection can be made to the solar module.
Using an aluminum framework, several
solar modules are mounted onto the roof of a home and are
wired together in series to produce a high voltage DC current.
Multiple series solar module circuits can be wired in parallel
to increase a solar system's power. See
Solar modules produce DC current. This
type of current is not compatible with your
your home's electric supply nor
is it compatible with the utility company's electric
grid so in must be converted to AC current. This is the job of
the DC to AC grid intertie inverter.
See image below.
The DC to AC grid intertie inverter not
only converts the solar module's DC current into AC current,
it also performs many other duties. Among them are:
1. The inverter constantly monitors the
utility company's electric supply for changes in voltage,
frequency and outages. The inverter is designed to
automatically shut down in the event of severe electrical
deviation or grid failure. The inverter does this not only to
protect itself from damaging currents but also to protect
unsuspecting utility line workers from being injured by
electric current generated by the inverter.
2. The inverter includes an LCD
display which provides the user with information concerning
the solar system's general performance including real time and
historical power production as well as the status of the
3. The inverter
also synchronizes the AC current that it produces with the
utility company's AC
current and then feeds that current through your utility meter
and on to the grid. Because you are producing power, your
utility meter will actually slow down and in many cases will
actually run backwards. If you are in a "Net Metering
State" such as California, your utility company is
required to credit you full retail price for the power that
Residential Solar Electric System Question and Answers
Do I have to
disconnect from the electric company ?
No, you remain connected to the power company, but instead of
only using the energy that the power company produces, you
actually become an independent power producer. Or in essence
your own power company.
electric systems have just about reached plug and play
simplicity. There are no moving parts to break, no critical
monitoring and virtually no noise. Solar modules simply sit in
the Sun and generate electricity, year in and year out, in
fact, the typical solar module carries a warranty of 25 years
and in most cases are expected to last double that amount of
Below is a graphic which
illustrates the basic configuration of a typical solar
electric system. The Solar PV Array or Photovoltaic Array on
the left is the actual energy collecting unit, it may be
mounted on the ground, on a a roof top or on a pole as
illustrated. The array should be pointed due South and tilted
so that there is maximum exposure to the Sun.
Will I be paid for the excess power that
I feed to the utility company ?
You won't receive a payment but you will
receive a credit from the utility company for the excess power
that you produce. In states that have enacted net metering
laws, the utility companies will actually issue you a credit
for the full retail value of the the power that you do not
consume. If you over produce power lets say in June, then that
over production credit is carried over to the subsequent
months until you credit is used up. On the anniversary date of
your system's installation, any remaining credit is zeroed out
and you start the year's energy production over again. This is
why it's important to limit the size your system so that you
reduce or eliminate your electrical consumption for the year
and not over produce.
Will I need batteries for my system ?
The choice of whether or not to use batteries is a personal one and there are tradeoffs involved . Both battery-less and battery backed up solar electric systems will perform grid intertie, meaning that they both will sell the surplus power that you produce back to your utility company, although there are efficiency differences when comparing both systems.
It is mainly during a utility power failure that the difference becomes obvious. With a battery-less system, should there be a power failure, the system is designed to automatically shut down. You will not have electricity available to your home until the utility company has restored their power.
The reason for this is a matter of safety. If the power has failed and the utility company has sent a lineman up a pole to implement repairs, the last thing you want to do is feed power down the line when the lineman thinks that the power has been cut. This is why the system has been designed to make it impossible to operate the inverter when there has been a power failure.
The battery backed up system utilizes a completely different design. Like the battery-less inverter, as long as the utility company's system is operating normally, your solar system will continue to feed power through you meter providing you with a reduction in your electric bill. In the event of a power failure the battery backed up system will also stop feeding power to the utility company for the same reasons mentioned above, the difference is that during a power failure the battery backed up system will divert
backup power to your home and not to the utility company thus
protecting anyone working on the power line.
Depending on the size of the battery pack that you choose you can supply your home with power for several hours or even days.
When the power company restores power, your system will automatically begin selling power back to the grid. Note : Because batteries are involved in a backup type system, the overall power production efficiency of a battery backed up system
will be less than that of an equally sized battery-less system.
The decision to choose a battery-less or battery backed up system mainly boils down
to the following issues: Do you need back up power during a power failure ?
Are you willing to sacrifice efficiency, which means less
payback from the utility company and are you willing to spend
the additional expense of replacing the battery pack every 5
to 6 years. When considering all the issues, most people opt
for the battery-less type system.
How do I determine what size solar system I'll need ?