Solar Power Home

This article is intended to guide you through the process of calculating the size and cost of a Solar photovoltaic (PV) system for a residential property in Austin Texas. It can be applied elsewhere but some numbers will need to be adjusted.

A professional evaluation is needed to get an accurate estimate of the size and cost required but this is a good starting point.

The billing unit used by most utility companies is the kWh. As a reference let’s look at an example, a 1000 watt (1000 watts = 1 kilowatt) hair dryer if run for 1 hour would consume 1 kWh of electricity.

There are a number of things that influence what size PV system you will require and therefore the cost of the system. Location, electric consumption, shading, and the direction of the panels will all need to be considered when you size your system.

It is necessary for you to determine your average daily electricity consumption. You can do this from your utility bill. Normally, you are charged per kWh consumed per billing cycle. The billing cycle is generally one month. Divide the total kWh used during the cycle by the number of days in the cycle to get the average kWh use per day. You should do this for 12 or preferably more cycles and find the average. In the US, the average daily residential usage is around 34 kWh per day. You can find estimates online if you do not have your own data.

At some point in the process you will need to decide what percentage of your electric will be provided by solar. This can be any amount up to 100% or more if you wish to provide for future increase or sell power back to the utility company. For our purposes here we will do our estimate with a desire to replace 50% of the US average or 15 kWh.

PV systems are measured in generating capacity in watts or kilowatts and not by square feet. A 1 kW system will produce 1 kW of DC electricity with one hour of direct sunlight (if all parameters are ideal). The DC electric must be converted to AC electricity to be used in your home. This process results in a total power loss of 7-10 percent. Therefore a 1 kW system will actually produce around 900 watt hours (0.9 kWh)per hour of sunlight, of AC electricity.

In the case of Austin which receives an average of 5.4 hours per day of direct or near direct sunlight, you can expect a 1 kW system to generate 4.86 kWh of AC electricity daily. 5.4 x .9 (90% of 1 kW)= 4.86 kWh. In our example we wish to replace 15.37 kWh/day. We therefore need a 3.16 kW system to generate an average of 15.37 kWh/day. We arrived at that by dividing 15.37 by 4.86.

The average cost of installed solar PV systems in the US is around $10,000/kW. Our final cost is determined by multiplying 3.16 by 10,000. Therefore our system would cost about $31,600 before credits and rebates. There are federal tax credits and Austin Energy offers a number of rebates as well.

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

Visit Austin Solar Solutions to use the solar calculator or for detailed reports about Federal tax credits, local rebates and answers to FAQ’s. Don’t reprint this exact article. Instead, reprint a free unique content version of this same article.