In order to
select an solar electric system for your home, it is important
to determine how much electricity you are currently consuming
and how much of that consumption you wish to eliminate. To
determine your current consumption simply gather your last 12
months electric bills, add the monthly total kilowatt hour usage
for each month together then divide that number by 12, that will
give you your average electrical consumption in kilowatt hours
per year. Or call your utility company and ask them to tell you
what your average monthly kilowatt hour consumption was for the
last year.
Once we know
your average consumption, it's a simple matter to choose a
system that will take care of what ever portion of your
electric bill that you wish to eliminate, whether that be 10
percent, 50 percent or even 100 percent of your bill !
A second consideration when
selecting a solar electric system for your home is whether or
not you wish to have back up power in the event of a power
failure or do you wish only to reduce your monthly electric
bill. You may think that's a silly question, after all you
wouldn't want to have backup power in the event of a power
failure ? But adding backup power to a solar electric system
comes at a price.
Basically, there are two
different types of solar electric systems available for home
use: The battery-less grid intertie system which only feeds
power back to your utility company, thus reducing your electric
bill and the battery based grid intertie system which not only
feeds power back to your utility company but also provides your
home with electricity in the event of a power failure.
The key word to consider here
is batteries. Batteries are expensive and require periodic
maintenance. Batteries also require additional hardware such as
cables, a disconnect switch, a containment box and must be
periodically replaced at considerable expense. Batteries are
also notorious for reducing the efficiency of a solar electric
system, in other words they reduce the amount of power that you
are able to feed back to the utility company. Batteries can also
be dangerous if caution is not used during their handling.
If backup power is an absolute
must for your home, then a battery based system is the only
option. On the other hand if you can tolerate the occasional
blackout, then a battery-less grid intertie system is the only
way to go. In a battery-less system there is virtually no
maintenance. System efficiencies are very high. There is no
periodic replacement of product. In other words a system that's
hassle free.
When shopping for a solar electric system for your home or
business, make sure that the dealer that you are speaking with
is quoting you in real world PTC rated watts
or kilowatts. In what appears to be an effort to inflate the
capabilities of the systems that they are selling, many dealers
on the Internet are only providing STC rated performance which
is unrealistic. Make sure when comparison shopping that you are
comparing apples to apples. Insist upon receiving an actual
system PTC rating which includes the efficiency
rating of both the modules and inverter. Solar Kits will always
post both the PTC and CTC ratings so that you get a true
comparison when shopping for a system.
STC
(unrealistic) in an acronym for
"Factory Standard Test Conditions" which is 1,000
watts per square meter solar irradiance, 1.5 Air Mass and a 25
degrees C. cell temperature. PTC
(Real world) is an acronym for "PV USA
Test Conditions" which were developed at the PV USA
test site at the University of Davis, California. The PTC rating
represents a more real life condition of 1,000 watts per square
meter solar irradiance, 1.5 Air Mass, and 20 degrees C. ambient
temperature at 10 meters above ground level and wind speed of 1
meter per second.
The ambient temperature rating
is a better standard than factory conditions because silicon
solar cells average about 20 degrees C. above ambient
temperature in the real world, cell voltage drops as temperature
increases. A module's power output in real life conditions is
lower than the power measured at the factory where cell
temperature is maintained at a controlled 77 degrees F. (25 C).
Cell voltage drops about 0.08 volts per degree C. in
environments which exceed 25 degrees C. Thus, an STC rating of
17 volts can actually become a PTC rating of 15 or 16 volts.
Using Ohm's Law, volts times amps is equal to watts which equals
power, so a reduced voltage, means reduced watts.
And finally, be cautious when
purchasing a system of this magnitude over the Internet. Get to
know who you're dealing with. Many websites on the Internet that
would appear to be large reputable companies are actually home
based affairs that operate from an impossible to trace POB
(PO Box). Remember,
you're about to give this individual your personal information
and more importantly your credit card number. Is his company
solvent ? Does he have insurance ? Does he really have the
items that you're about to purchase in stock ? Does he
have any stock ?
Even if you don't live nearby, ask the dealer if you can get
directions to his place of business so you can stop by and take
a look at some products. If you cant get directions or a
straight answer from him, then in our opinion, steer clear !
It's important to remember that it takes only minutes to upload
a website to the Internet and only seconds to take it down.
If you
would like to learn more about protecting yourself when shopping
on the Internet
Click Here
