What value of electricity could I expect my system to produce over its lifetime?
We expect the LG panels to last for in excess of 25 years and so for your return on investment calculations we have assumed 25 years. You return will be affected by a wide range of factors which will continue to change, such as the annual cost of electricity in kW/h, the tariff you are on, the feed in tariff return you can expect and where you are located and therefore the amount of sun your system is likely to receive.
Other factors to consider are: How much electricity you consume during the day, which you would have had to pay for in the past and which is now generated by your solar system.
Lets also use a specific example. In our sample, in a city in NSW a 5kW solar system will generate 7000kWh of electricity per year. 5000kWh are used during the year by the owner. Normally they pay 30c per kWh to the energy retailer. Therefore the value of this electricity is $1500. The remaining 2000kWh are exported to the grid and the energy retailer will pay the owner 8c a kWh. Therefore the value of the exported electricity is $160. In total the value of the one year solar generation is therefore $1660 ($1500 self consumption + $160 export feed in tariff payment). If this 5kW system did cost $9130, the Return on investment will be 5 1/2 years, as 5.5*$1660 = $9130.