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Homeowners wanting to reduce or eliminate their electric bill 

 

Thousands of 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 businesses. 

 

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 the Sun.

 

 

How a solar system produce electricity for your home.

 

A residential 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 solar cell.

 


 


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 image below.

 

 

 

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 inverter itself.

 

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 you produce.

 

 

 

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. 

 

Solar 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 time.

 

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 ?

Although we don't mind it, we hear the same question a dozen times a day "I have a 2,000 square foot home, what size solar system do I need ?" or I have an average sized home with average appliances, what size system do I need ?" We've been designing solar systems for a long time and one thing that we've learned though the years is that the size of the home has absolutely no bearing on the size of the system.

 

We've seen customers with 1,200 sq foot homes that consume 3,000 kWh per month and then we've seen customers with 2,800 sq ft home that consume 1,000 kWh per month. The size of the system boils down to, how much electricity do you consume in kilowatt hours and much much of that consumption would you like to eliminate. 

 

It's best to call one of our representatives and let them calculate an appropriate system size that will meet your needs. But in a nutshell we will need to know your average monthly or daily electrical usage in Kilowatt hours or Kwh, you can obtain this information by calling your utility company and ask them for this data. Be sure to determine whether the number that they are providing you with is Kilowatt hours per day or Kilowatt hours per month.

 

Although the following method is not as accurate as calling your utility company, you can approximate this number if you have a few copies of your electric bill. What you will need is a copy of your bill which represents your average Winter usage lets say January as well as your average Summer usage, lets say July. Add the two bills together and then divide the sum by two. For example if your Winter monthly usage is typically 600 Kwh and your Summer usage is typically 1,000 Kwh then your average monthly Kwh would be approximately 800 Kwh.

 

Next we will need to determine your average daily usage. This is simply done by taking the average monthly Kwh number and divide it by 30 days. In the above example 800 Kwh per month divided by 30 days equals 26.67 Kwh per day. This is how much power your system will need to produce per day in order to approximately eliminate you electric bill.

 

Next we must take the daily Kwh number and divide it by the average number hours of full sunlight that is available to you on a daily basis. In California for instance, that number is approximately 5 hours. There is obviously more sunlight available during an average day especially in California, but what we're concerned with here is FULL sunlight. 

 

So in our above example 26.67 Kwh or 26,670 watt hours, ( Remember Kilo means One Thousand ) divided by 5 hours equals 5.33 Kwh or 5,334 Watt hours.

 

Finally we will need to factor in the size of the solar module that we are using and we'll know how many modules we'll need to approximately eliminate the above mentioned electric bill. 

 

A typical sized module used in this type of system has a PTC adjusted rating of 103.9 watts. So we would take the 5,334 Watt hours mentioned in the above calculation and divide that number by 103.9 watts per module and we get 51.338 modules. There is no such thing as .338 of a module so we will need to round up to 52 modules.

 

The above example would apply if you wanted to eliminate your bill, cut it in half or eliminate what ever increment you wanted from your bill. Simply take the number of modules that you would need to approximately eliminate your bill and multiply that number by .75 to approximately reduce your bill by three quarters, .50 to approximately reduce it by half or .25 to approximately reduce it by one quarter.

 

The above calculations may seem a bit daunting but don't worry, that's what our staff is here for. We're experts at helping you to choose the perfect system for your needs, whether that is to reduce your bill by 10% or eliminate it entirely. Just give us a call 1-888-955-3471

 

 

 

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