Solar Electric Archive

In this article we will go through the process of determining the size and cost of a photovoltaic (PV) system for a home located in Austin, Texas. The same method can be used in other locations with minimal adjustments.

This is important information to have prior to consulting a professional who will provide a more definitive estimate. It’s also a good place to begin if you are considering installing a system your self.

The term kWh represents one kilowatt hour. This is a unit of energy most often used as a billing unit by utility companies. A 100 watt (0.1kilowatt) light bulb consumes 100watts/hour or .1 kWh if operated for one hour.

A number of factors will alter the required size and cost of a PV system. These include the amount of shading your panels will be subject to, the efficiency and cost of the PV panels you choose, the direction the panels are facing, your home’s location etc.

The first step in determining the size and cost of solar panel installation in Austin or anywhere, is determining your electric consumption. The easiest and probably most accurate way is to simply look at your electric bill. That of course assumes you have been living in the home for which you are going to install solar. It is best to do this with at least 12 monthly bills. Look at the number of kilo-watt hours (kWh) used during the billing cycle and then divide by the number of days in a billing cycle. The result will be the number of kWh per day that you consume. This number will vary from month to month. You can add the daily averages from each month and divide by the number of months to determine an average daily amount. For example the average US home uses about 935 kWh/ month or 30.74 kWh/day.

Then you will decide how much of your current usage you will be replacing with solar generated electric. In the case of the example above, if we choose to replace 50%, we will need to generate, on average 15.37 kWh/day (30.74 kWh x 0.5).

Solar systems are not measured in square feet or meters but in kW generating capacity. A 1 kW solar system will generate one kWh of DC current with one hour of direct sunlight. The electric used in most American homes however is AC. The electric from the solar panels must be converted to AC and this conversion results in the loss of about 10%. As a result you will receive about 900 watt hours (0.9 kWh) of usable AC, with a one kW system receiving one hour of direct sun.

The next piece of information need is the average daily hours of direct sunlight in your area. Austin, Texas receive an average of 5.4 hours of direct sun daily. Therefore you can expect a 1 kW PV system to produce 4.86 kWh daily (5.4 X 0.9 =4.86). In our example we want to generate 15 kWh per day. We divide 15 by 4.86 and get 3.09. Therefore we will need approximately a 3 kW PV system to generate 15 kWh per day.

In the US, the current average for an installed PV system is about $10,000 pew kW of system. We multiply our 3 kW of system times 10,000 and see that our 3 kW system will be about $30,000 installed. That is a considerable amount but the good news is that there are significant tax credits and rebates to off set this cost. Also, PV panels are continuing to become more affordable as more are produced more efficiently.

You can receive free reports detailing tax credits and rebates by going to http://austin-solar-panels.com. There is also a solar calculator that will easily perform all the above calculation for you.

At Austin Solar Solutions you can receive free answers to FAQ’s, Federal tax credit reports, a solar calculator and more.

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